Synthesis of Polyethylene-Based Materials, Ion Exchanger, Superabsorbent, Radiation Shielding, and Laser Ablation Applications

Abstract

Polyethylene (PE), ion exchangers and membranes, super absorbents, radiation shielding, and laser ablation are covered initially. In the second part, studies on polyethylene-based ion exchangers and membranes are given. Ion exchangers and membranes chemically modify copolymers to exchange ions in the electrolyte solution. The third segment covers research on polyethylene-based super absorbent copolymers and composites for water retention and heavy metal contamination removal. Super absorbent polymers are hydrophilic, water-insoluble polymers that absorb plenty of water. With their expansion capacity and user-friendliness, super absorbents are widely used in various fields such as biomedicine, drug distribution, personal care products, batteries, tissue engineering, construction, food packaging, heavy metal separation, electronics, cables, cosmetics, and agriculture. Polyethylene-based polymeric composites are used more to minimize radiation. PE’s high hydrogen concentration absorbs neutrons, making it a radiation shield. Block copolymers of polystyrene-b-poly-ethyleneglycol and boron nitride particles can make selenium dioxide a structural material and radiation barrier when paired with nanostructures. The fourth section examines the optical and conductivity properties of laser-ablated polyethylene nanocomposites with metal oxide nanoparticles. Laser ablation polishes metal, transparent materials, composites with surface and interior changes, and nanomaterials. Polymer laser ablation improves surface modification and thin layer deposition. Laser wavelength affects UHMWPE wettability.

1. Introduction

Polyethylene (PE), a polymer of great significance and utility, has been subject to extensive research as a plastic material [1, 2, 3, 4, 5, 6]. PE is widely recognized as a highly advantageous plastic material for commercial applications due to its exceptional mechanical properties, notable flexibility, commendable chemical resistance, lightweight nature, favorable thermal stability, and cost-effectiveness [7, 8]. The size of the global PE market was assessed at USD 105.77 billion in 2022 and is anticipated to increase from USD 110.23 billion in 2023 to USD 146.20 billion by 2030, demonstrating a compound annual growth rate (CAGR) of 4.1% throughout the forecast period [9]. PE is utilized in various industries, such as agriculture [10], manufacturing [11, 12], medicine [13, 14], construction [15], packaging [16], energy [17], outdoor items [18], and others, owing to its advantageous technical properties and cost-effectiveness in comparison with alternative materials.

PE can be classified into two primary categories: High-density polyethylene (HDPE) is characterized by its elevated density and notable resistance to elevated temperatures. This material is commonly employed due to its notable mechanical strength and chemical resistance. Polyvinyl chloride (PVC) is a resilient and environmentally sustainable polymer that finds extensive utilization in various domains, including water pipe systems, water storage containers, plastic bottles, toys, and packaging materials. Low-density polyethylene (LDPE) is a variant of PE characterized by its reduced density and enhanced flexibility in its molecular structure. Seamless plastic bags are commonly employed in a range of applications, including plastic films, closures, coatings, and diverse packaging materials. PE offers several advantages: The polymer in question is characterized by its widespread availability and relatively affordable cost. Due to its lightweight nature and malleability, this material finds extensive utilization across a wide range of applications. The material exhibits resistance to various chemicals and demonstrates waterproof characteristics. Recycling is a straightforward process that allows for the reuse of materials. However, PE also possesses certain limitations: The material exhibits sensitivity to ultraviolet (UV) radiation and elevated temperatures, thereby leading to the occurrence of cracks and alterations in coloration when employed in outdoor environments. At low temperatures, it has the potential to exhibit brittleness. The process of biodegradation is characterized by a lengthy duration, resulting in the potential for environmental pollution. Hence, the significance of recycling and the utilization of PE in environmentally sustainable practices cannot be overstated. The mitigation of PE’s environmental impact can be achieved through the implementation of measures, such as the reduction of single-use plastic products and the enhancement of recycling infrastructure.

Ion-exchange polymers refer to a kind of artificial ion-exchange resin that is composed of cross-linked organic copolymers. These copolymers possess functional groups that have been incorporated into a copolymer matrix through a chemical modification process. These functional groups have the ability to dissociate and exchange ions with ions derived from the surrounding electrolyte solution. Spherical granules, which are insoluble in both water and organic solvents, are often acquired [19]. Ion-exchange membranes (IEMs) play a significant role in a wide range of technologies, primarily due to their crucial characteristics of perm-selectivity and resistance. The membranes can be categorized into two types: heterogeneous membranes, which are created by combining an ion-exchange resin and a thermoplastic polymer, and homogeneous membranes, which possess ion-exchange groups that are chemically attached to a cross-linked backbone [20, 21]. Membranes are classified as anion-exchange (AEM) and cation-exchange (CEM) membranes based on their level of selectivity. The utilization of ion-exchange (IE) procedures has demonstrated its effectiveness in the removal of natural organic matter (NOM), heavy metal ions, and lanthanides. An examination was conducted to examine the sorption and separation of lanthanides using ion exchangers of different types [22, 23]. A set of anion-exchange membranes (AEMs) was made utilizing a straightforward casting approach, employing polyvinyl alcohol/branched polyethyleneimine (PVA/BPEI) as the main components and glutaraldehyde (GA) as the cross-linking agent. The swelling ratio (expressed as a percentage) and ion-exchange capacity (IEC, measured in milliequivalents per gram) of PVA/BPEI were determined to be 99.25% and 3.01 meq/g, respectively [24].

The significance of efficient water resource management is growing, necessitating the implementation of a comprehensive system that encompasses an efficient irrigation infrastructure, minimizes water wastage, and incorporates suitable agricultural practices. Naturally occurring chemicals and heavy metals are introduced in significant quantities into several environmental compartments by anthropogenic activity. As a consequence, the capacity of the environment to support life is diminished, posing a threat to the well-being of humans, animals, and plants [25]. Superabsorbent polymers(SAP) demonstrate a high capacity to absorb water and other chemicals due to their cross-linked architectures, which render them insoluble in water. The utilization of SAP in membrane and agricultural contexts holds significant significance [26]. Furthermore, these materials have applications in the sectors of bioengineering, medicine, and cosmetics. The escalating utilization of radioactive elements contributes to the escalation of radioactive pollution, necessitating the development of modern materials for the purpose of safeguarding humans. Scholars have extensively investigated compounds that provide shielding against irradiation, namely those based on polymers (such as gamma and electromagnetic radiation) [27, 28].

The process of synthesizing colloids using lasers involves the combination of light and nanotechnology, resulting in an increased production yield of nanomaterials throughout the synthesis process. Additionally, this method has the advantage of reducing the cost per unit of laser power required for the synthesis, as stated in Ref. [29]. The utilization of laser ablation in liquids (LAL) has been identified as a viable approach for the production of diverse nanostructures in an efficient and scalable manner [30].

2. Ion exchanger

The distinctive characteristics of ion exchangers can be elucidated by their structural composition, which, as per the prevailing definition, consists of a framework that possesses an excess positive or negative charge, offset by counterions of opposite polarity. Due to the high mobility of counterions, they exhibit a propensity to be readily substituted by ions of equivalent charge. The ion-exchange capacity of an ion exchanger refers to the quantity of counterions present in its content. Selectivity is a significant attribute of ion exchangers, often referred to as the capacity to differentiate between various counter-ion species [31]. Ion-exchange resins are widely utilized in the nuclear industry for the purpose of eliminating radioactive impurities, including neutron activation products and fission products, that may have been released from fuel elements [32].

In their study, Savaskan et al. [33] made block copolymers of polystyrene and poly(ethylene glycol) (PEG) by copolymerizing styrene with two different initiators: PEG-dimethacrylate (PEG-DM) and macromonomer initiators (MIM). The PEG-DM exhibited PEG values of 400, 600, 1000, 1500, 3000, 10,000, and 35,000, while the MIM had PEG values of 400 and 1500. The extent of swelling in water (H₂O) or chloroform (CHCl₃) of both the sulfonated and unsulfonated block copolymers was assessed using similar experimental conditions, revealing significant variations. The investigation focused on examining the ion-exchange capacity and selectivity coefficients of the ion-exchange resins. The ion exchangers that were acquired exhibited a range of capacities, spanning from 0.4 to 2.9 meq/g. The synthesis of polymer-based ion exchangers, also known as ion-exchange resins, was initially conducted in the 1930s [34]. The cross-linked PS-PEG ion exchanger is shown in Figure 1.

Figure 1.

The cross-linked PS-PEG ion exchanger.

The phenomenon of ion exchange takes place when there is interaction between an ion exchanger and a solution. The swelling ratios of ion exchangers were observed to decrease as the degree of cross-linkage increased. In the presence of an extensive quantity of ion-exchanger resins, the system would reach a state of equilibrium. At this equilibrium, the system’s free energy would decrease due to the inclusion of water through the process of diluting the internal solution. This dilution would result in the release of free energy associated with mixing and a subsequent reduction in the electrostatic repulsion between adjacent fixed ions. The limitations of this process arise from the finite elasticity of the resin, which is constrained by the cross-linking mechanism. The majority of ion-exchange resins were synthesized using cross-linked copolymers of styrene and divinylbenzene, which were shaped into beads. This study pertains to the synthesis of ion exchangers using styrene PEG-DM-400, PEG-DM-600, PEG-DM-1000, PEG-DM-1500, PEG-DM-3000, PEG-DM-10,000, and PEG-DM-35,000 as starting materials. The researchers endeavored to synthesize cation-exchange resins containing PEG units through the polymerization of styrene with PEG-DMs or MIMs, followed by the sulfonation process of the resulting cross-linked polymers. In order to examine the impact of polymerization time on the degree of cross-linkage and ion-exchange capacity, the block copolymerization reaction was conducted for a duration of 3 and 22 hours. In order to achieve the desired objective, the process of polymerizing cross-linked poly (styrene-b-PEG) was conducted following the procedure outlined earlier. The swelling ratios observed in water cross-linked polymers were found to be significant, ranging from 48 to 313 weight percent. In terms of comparison, it was observed that the swelling ratios of the resins subjected to a shorter polymerization time (e.g., 3 hours) exhibited higher values compared to those subjected to a longer polymerization time (22 hours). The ion-exchange resin’s capacity is contingent upon various factors, including the duration of the reaction, the molecular weight of the macro-crosslinkers, and the degree of cross-linkage. When the polymerization time was 22 hours, the experimental findings indicated that ion-exchanger resins exhibited a reduced ion-exchange capacity. In particular, the ion-exchange capacity of the ion-exchanger resins decreased as the polymerization time, degree of cross-linking, and molecular weight of the crosslinker all went up. The presence of polar sulfone groups in resins contributes to a higher swelling ratio of cation exchangers in water compared to the untreated cross-linked block copolymer. In the final column, the calculated capacities exhibit higher values compared to the corresponding experimental capacities. In this manner, the sulfonation of the inner core of the resin does not have an impact on the ion-exchange reaction.

Eui-Soung Jang and his colleagues [35] did a study to find out how the amount of water in polymers affects the rate of diffusion of alkali metal chlorides (specifically LiCl, NaCl, and KCl) in cross-linked poly(ethylene glycol) diacrylate (XLPEGDA) hydrogels. This study is a component of a wider endeavor aimed at comprehending the fundamental mechanisms underlying water and ion transportation in hydrated polymers. The determination of salt diffusion coefficients (Ds) was achieved through the utilization of salt permeability and sorption measurements. Hydrogels composed of XLPEGDA were synthesized utilizing three distinct water contents, specifically 50, 67, and 93 grams of water per gram of dry polymer. The Ds of alkali metal chlorides within XLPEGDA polymers exhibited an upward trend with the increase in water content. The utilization of the Mackie and Meares model, which incorporates the influence of polymer chain obstruction (also known as tortuosity) on the diffusion of salt in hydrated polymers, was employed in the analysis of salt Ds. The observed salt diffusion coefficients in these polymers align with the theoretical model, indicating a general trend. The determination of individual ion diffusion coefficients in the samples was achieved by integrating data on salt permeability/sorption with results from ionic conductivity measurements. The Ds of chloride ions exhibited uniformity across all salts. The sequence of alkali metal ion Ds observed in these polymers differed from that observed in aqueous solution, specifically with Ds K⁺ > Ds Na⁺ > Ds Li⁺. Furthermore, it should be noted that the aforementioned order is subject to variation depending on the water content of the polymer. This observation implies that the diffusion behavior of alkali metal chlorides in XLPEGDA polymers is affected by both the hydration of ions and the specific interactions between the polymer and ions.

The present investigation selected alkali metal chlorides, such as LiCl, NaCl, and KCl, as the subject of study in order to examine the impact of ion charge density and size on diffusion within hydrated polymers. The utilization of XLPEGDA is employed as a representative polymer system in this study. The polymer in question lacks substantial electrostatic interactions between ions and polymers, allowing for a methodical examination of the influence of polymer water content on ion diffusion without substantial modification to the polymer’s fundamental chemical composition. Samples of XLPEGDA with three distinct water uptake values were produced by altering the initial water content during the pre-polymerization stage. The calculation of salt Ds was performed by utilizing salt permeability and sorption data, employing the solution-diffusion model. The Ds were compared to a model proposed by Mackie and Meares, which takes into consideration the impact of polymer chain obstruction, also known as tortuosity, on the diffusion of salt in hydrated polymers. The measurement of ionic conductivity in polymer samples was conducted through the utilization of electrochemical impedance spectroscopy (EIS). This technique was then coupled with salt permeability/sorption data in order to determine the individual ion Ds for each polymer sample.

According to Feng et al. [36], sulfonated materials have been widely used in a variety of membrane applications because of their noteworthy qualities such as improved electrical conductivity, admirable chemical stability, hydrophilic nature, and decreased susceptibility to fouling. The presence of fixed charged groups and the hydrophilic nature of sulfonated polymers not only confer enhanced physicochemical properties suitable for membrane applications, but also induce notable alterations in the process of membrane formation. PEG has been extensively employed as an additive for the production of membranes from polymer solutions using the non-solvent induced phase separation (NIPS) technique. The present study aims to investigate and compare the effects of sulfonated polyphenylenesulfone (sPPSU) solutions with those of polyphenylenesulfone (PPSU) solutions, considering various thermodynamic and kinetic factors. The study revealed several key findings: Firstly, it was observed that PEG exhibited hydrogen bonding interactions with sPPSU. Secondly, the introduction of PEG into sPPSU solutions resulted in an increase in viscosity due to enhanced polymer interaction and entanglement. Lastly, the presence of PEG had a retarding effect on phase inversion and inhibited the formation of macrovoids. Furthermore, when an optimal concentration of PEG is incorporated into the dope solution, the resulting membrane exhibits enhanced mechanical integrity, increased hydrophilicity, and improved permeability characteristics. To the best of our knowledge, this study represents the inaugural investigation into the functions of PEG in the production of asymmetric membranes derived from sulfonated polymers. This study has the potential to elucidate the molecular interactions between PEG and syndiotactic polyphenylsulfone (sPPSU), thereby offering valuable insights for the development of membrane fabrication protocols.

The continuous advancement of polymeric membranes for industrial applications has been a subject of research and development for several decades. Sulfonated polymers have garnered significant interest in recent years due to their charge characteristics, which impart membranes with exceptional physicochemical properties that are well-suited for a diverse array of applications [37, 38, 39, 40]. Previous studies have demonstrated that membranes derived from ultrafiltration and forward osmosis exhibit enhanced resistance to fouling and improved permeation properties, making them highly suitable for applications in water purification [41, 42, 43]. According to a study [44], the inclusion of sulfonic acid groups in the nanofiltration process resulted in enhanced rejections of ionic solutes. Through precise manipulation of the fabrication process, the sulfonated polymers can be customized to suit a wide range of applications and processes.

In their study, Kamcev and colleagues [45] carry out a comprehensive examination of the impact of fixed charge group concentration on the diffusion coefficients of salts in ion-exchange membranes. Cation- and anion-exchange membranes (CEMs and AEMs) with varying concentrations of fixed charge groups and comparable levels of water content were successfully synthesized using a one-step free radical copolymerization reaction. The investigation of ion transport through membranes, driven by concentration gradients, involved the measurement of salt permeability coefficients. These coefficients were measured as a function of salt concentration in the upstream solution. The salt permeability coefficients of all membranes exhibited a notable increase of approximately tenfold as the salt concentration in the external solution increased from 0.01 to 1 M. This increase can be primarily attributed to similar enhancements in salt partition coefficients. The salt permeability coefficients for both series of membranes exhibited a decrease in average values as the concentration of fixed charge groups increased with a similar magnitude of reduction. The apparent salt diffusion coefficients, obtained from the salt permeability and salt partition coefficients using the solution-diffusion model, exhibited a more pronounced variation for the AEMs compared to the CEMs despite similar alterations in the concentration of fixed charge groups within the membranes. The observed variations in apparent salt diffusion coefficients between AEMs and CEMs were ascribed to disparities in the membranes’ free volume. The hypothesis put forth in this study received support from measurements conducted using positron annihilation lifetime spectroscopy. These measurements revealed differences in the lifetime values of ortho-positronium, which serves as an indicator of the size of free volume elements within the membranes. These variations were found to be correlated with differences in the apparent diffusion coefficients of salt.

In a study by Qitao Hu et al. [46], it was discovered that the hydrophobic interaction between ions in a complex analyte could make it challenging to detect ions utilizing membrane-based ion-selective sensors. This study showcases the potential of mitigating interference caused by hydrophobic interactions on sensors through the integration of hydrophilic PEG into the membrane. The sensor employed in this study is a silicon nanowire field-effect transistor (SiNWFET) that has been modified on its surface with a mixed-matrix membrane (MMM) containing an ionophore. The ionophore used in the MMM can be either a commercially available Na-ionophore III or a newly developed synthetic metal-organic supercontainer. The inclusion of PEG hinders the distribution of hydrophobic ions within the MMM, thereby diminishing their impact on the identification of desired ions. This is supported by empirical evidence demonstrating a significant enhancement in the ability to selectively detect Na⁺ ions in the presence of interfering methylene blue (MB⁺) ions, surpassing a tenfold increase in selectivity. The utilization of a SiNWFET sensor array allows for the detection of Na⁺ and MB⁺ in a multiplexed fashion while maintaining controlled susceptibility to cross-interference and significantly expanding the dynamic range. The detection of ions in liquid samples, such as river water, sweat, and serum, holds significant importance in the fields of environmental monitoring, disease diagnosis, and medical analysis [47, 48, 49, 50]. The utilization of sensors integrated on a single chip enables the simultaneous detection of multiple target ions, facilitating the acquisition of comprehensive and complementary information regarding the analyte [50, 51, 52]. Nevertheless, it is important to note that in practical applications, liquid samples typically consist of intricate constituents, including elemental ions, molecular ions, and biomolecules. The presence of intricate components has the potential to disrupt the functionality of ion sensors, leading to the generation of inaccurate and irrelevant responses. This interference can result in selectivity issues [52, 53, 54].

Kulshrestha and colleagues [55] present in their study a comprehensive analysis of the extensive production and characterization of interpolymer ion-exchange membranes (IEMs) based on PE. Furthermore, they assess the performance of these membranes in the context of water desalination through electrodialysis. The CEM was fabricated using a cross-linked film made of PE and polystyrene interpolymers. Similarly, the AEM was prepared using a cross-linked film made of PE and polypmethylstyrene interpolymer through an appropriate functionalization reaction. Both the prepared CEM and AEM demonstrated an ion-exchange capacity of 1.5–1.30 meq g⁻¹, ionic conductivity ranging from 2.85–1.15 mS cm⁻¹, and transport numbers of 0.92–0.93, respectively. The AEM and CEM were employed in the desalination of brackish water with a total solid content ranging from 2000 to 3000 mg/L. This process was carried out using a unit with a size of 200 cm², utilizing 30 membranes of each type. The desalination was conducted in a single-pass mode, resulting in a final flow rate of purified water ranging from 7.2 to 8.4 L/h. The desalination processes exhibited power consumption values ranging from 0.789 to 0.796 kWh/kg, while the current efficiency ranged from 87 to 86%. In contrast, the W and CE% values observed for the commercial membrane (IONSEP) during water desalination under similar experimental conditions were found to be 1.125–1.07 kWh/kg and 61–64%, respectively. The aforementioned values demonstrate the superior performance of the developed membranes and confirm the successful implementation of the process on a large scale. Table 1 presents the ion-exchange capacity (meq/g) and swelling ratios (%) of ion-exchange resins and membranes that incorporate polyethylene glycol and polyethylene.

Sample	Ion-exchange capacity exp (meq g^−1)	Swelling ratio (%)
R-DM-400 [33]	2.82	311.00
R-DM-600 [33]	2.04	300.00
R-DM-1000 [33]	0.55	133.46
R-DM-1500 [33]	1.81	280.80
R-DM-3000 [33]	0.30	399.23
R-DM-35000 [33]	1.00	467.54
CA200 [45]	2.04	—
CA238 [45]	2.48	—
CEM-1 [55]	1.43	—
AEM-1 [55]	1.00	—
PE-g-PVBC-TOH (8.3%) [56]	0.40	9.46
PE-g-PVBC-TOH (12.6%) [56]	0.49	14.67
PE-g-PVBC-TOH (15.7%) [56]	0.58	22.53
PE-g-PVBC-TOH (17.4%) [56]	0.63	23.05
PE/PSt [57]	1.32	—
PE/P4-MS [57]	1.30	—
Ionsep [57]	2.20
Nafions [58]	0.84	16
Neoseptas [58]	1.78	17
CMX MSC-0-23 [58]	1.60	26
MSC-0-31 [58]	1.98	25
MSC-1.5-27 [58]	1.73	23
MSC-3.5-29 MSC-3.5-32 [58]	1.57	22
MSC-3.5-32 [58]	1.65	20

Table 1.

The ion-exchange capacity and swelling ratios of some ion-exchange resins and membranes.

Ion-exchange membranes can be categorized into two main types: CEMs and AEMs, based on the specific functional group that is attached to the surface of the membrane [59, 60, 61, 62]. The inter-polymer membrane, which is composed of PE and polystyrene, exhibits several advantageous characteristics. Firstly, it possesses a morphology wherein the ionic phase is dispersed within a hydrophobic matrix. Additionally, this membrane is cost-effective and can be easily processed. The AEMs fabricated utilizing CME exhibit high efficiency across various applications. Nevertheless, in light of the potential harm to human health caused by this process, alternative methods have been utilized for the preparation of AEM. A novel AEM based on the inter-polymerization of PE and polyp-methylstyrene (P-MS) through benzylic bromination was synthesized and employed for the purpose of water desalination [34]. This study showcases the extensive production of CEM and AEM through the utilization of inter-polymer films composed of PE and polystyrene (PSt) for CEM and PE and poly(methyl methacrylate-co-styrene) (PMS) for AEM. These membranes were subsequently employed in the process of electrodialysis (ED) for the desalination of brackish water. The desalination efficiency of these membranes has been evaluated in comparison with the commercially available membrane (IONSEP), as well as the AEM based on PE/PSt interpolymer prepared through conventional means using CME. Research has indicated that the efficiency of a PE/PMS membrane is similar to that of a PE/PSt membrane.

In their work, Mourad Amara et al. [63] examined the utilization of commercial polymer cation-exchange resins for the purpose of separating and recovering Cu(II) and Ag(I) from synthetic solutions. After altering the properties of the cation-exchange resin through the fixation of organic macro-cations under different experimental conditions, these substances exhibit a range of ionic species. The modification process involved impregnating the resin under varying conditions, such as immersion time, concentration, and pH. This was done by immersing the resin into solutions containing tetramethylammonium, tetrabutylammonium, and polyethyleneimine. The determination of the selectivity coefficient and resin capacity for the ions Li(I), K(I), Fe(III), Cu(II), Ag(O), and Cd(II) was conducted in batch operations. Additionally, the kinetics of metal adsorption by both the modified and unmodified resins was investigated. Following the adsorption of the organic macro-cation, the ion-exchange capacity exhibited variability, resulting in a decrease in the rate of the ion-exchange reaction for monovalent ions. However, the modification of the cation-exchange resin in a polyethyleneimine solution led to an increase in the exchange capacity specifically for copper ions. In the conducted batch experiments, various stripping solutions were evaluated for their effectiveness in recovering metals that had been loaded onto the resin during the adsorption operation. These solutions included SCN 0.01 M, HNO₃ 0.5 M, HNO₃ 1 M, and thiourea 0.1 M in HNO₃ 0.5 M. The obtained results were as follows when the tested solutions were composed of a mixture of ions adsorbed in the resin. The elution efficiency of Cu(II) immobilized on PEI-modified resin using acids exhibited a 30% decrease in comparison with the 65% elution efficiency observed with unmodified resin. In contrast, it was found that a solution containing thiourea at a concentration of 0.1 M in nitric acid at a concentration of 0.5 M exhibited the highest efficacy in eluting both silver ions (Ag(I)) and copper ions (Cu(II)), resulting in an equal recovery rate of 80% for each metal.

The physicochemical properties of experimental heterogeneous MK-40 and MA-41 membranes, composed of varying ratios of ion-exchange resin and PE binder, were investigated by V.I. Vasilieva et al. [64] in their study. The data demonstrates that the specific electrical conductivity in NaCl solutions ranging from 0.01 to 1 M exhibits a threefold decrease for cation-exchange membranes and a twofold decrease for AEM as the ion-exchange resin content in the membranes decreases from 69 to 55%. The sensitivity of diffusion permeability in AEM to their composition has been established, whereby an increase in the proportion of ion-exchange resin in the composition naturally leads to an increase in permeability. The impact of the diverse composition of a membrane on its structure, as determined through standard contact porosimetry, is further enhanced by calculating the transport-structural parameters of both the micro-heterogeneous and extended three-wire models of the ion-exchange membrane. The investigation into the interplay between composition, structure, and properties is a fundamental inquiry within the field of membrane materials science [65]. Previous research has investigated the impact of the ion-exchange resin proportion in CEMs on the advancement of electroconvection. However, it is important to note that these studies were conducted using samples of Ralex CM (MEGA a.s.) from foreign sources.

The study conducted in Refs. [66, 67] examined the impact of the PE to polystyrene sulfonic cation-exchange resin ratio on the conductive properties of the MK-40 membrane, which is manufactured by Shchekinoazot in Russia. In the practical application of high-intensity electrodialysis and electrodialysis preconcentration of electrolyte solutions, it is crucial to determine the acceptable ranges of variation in the ratio between the ion-exchange resin and the inert binder. These ranges should ensure that there are no substantial alterations in both the specific electrical conductivity and the diffusion permeability of the membranes. No investigations have been conducted on heterogeneous CEM and AEM. Therefore, the investigation of the structural and electro-transport properties of heterogeneous membranes containing varying proportions of ion-exchange resin and inert polymer remains pertinent. The objective of this study was to investigate the impact of the composition of heterogeneous membranes MK-40 and MA-41 on their structural and electro-transport properties. The objective of this study was to conduct an experimental investigation on the electrical conductivity, diffusion permeability, and water distribution across different binding energies and pore radii in heterogeneous membranes. These membranes were composed of varying amounts of resin and PE. Additionally, the transport and structural parameters of the membranes were calculated using the two-phase and extended three-wire models of ion-exchange material conductivity. The aim was to gain new insights into the influence of membrane composition on their structure and properties, and to evaluate their potential applications in electromembrane processes.

In their study, Naim et al. [68] discuss the preparation of heterogeneous membranes through the incorporation of ion-exchange (IE) resins, specifically cation or anion resins, into a polymer matrix. This integration ensures that the resin is uniformly distributed within the polymer, resulting in a homogeneous structure. This study focuses on the fabrication of new membranes and the investigation of various variables. These variables include the type of polymer matrix used, specifically cellulose acetate (CA) or cellulose acetate butyrate (CAB), as well as the source and properties of the CA. Additionally, the study examines de-esterified membranes, different types of ion-exchange (IE) resins (cationic, anionic, or nonionic), and the use of either ground or pristine resins. The experimental results revealed that the utilization of ground resins led to the production of thinner membranes that exhibited enhanced perm-selectivity for both cationic and anionic ion-exchange resins, using the two tested brands of cellulose acetate. The nonionic ion-exchange resin yielded anticipated unfavorable outcomes, particularly when it underwent pulverization prior to its amalgamation with the polymers. The results obtained from the CAB polymer were found to be unfavorable in comparison with the two types of CA polymers investigated. Additionally, the CAB polymer exhibited lower perm-selectivity, particularly when the IE resins were ground prior to their incorporation into the CAB polymer. Bouzek et al. [69] prepared ion-exchange membranes with heterogeneous characteristics by blending sulfonated poly(1,4-phenylene sulfide) or sulfonated styrene–divinylbenzene copolymer particles with a matrix polymer. A total of four different types of polymers were utilized in this study as a matrix. These polymers included highly flexible linear PE, moderately flexible fluoroelastomer, rigid polystyrene (all of which exhibit high hydrophobicity), and hydrophilic cellulose that was prepared through the process of hydrolysis of CAB. The investigation of membrane morphologies was conducted using scanning electron microscopy (SEM), infrared spectroscopy (IR), and density measurements.

3. Superabsorbent polymers

SAPs are a class of polymeric materials that exhibit exceptional water absorption properties. Superabsorbent materials, known as “slush powder” in the scientific literature, are composed of a complex three-dimensional structure of hydrophilic polymers that are cross-linked. These polymers, which can be linear or branched, possess the ability to absorb and retain a wide range of fluids, including bodily fluids and blood solutions [70]. The master’s project submitted to the patent by the research group led by Savaskan Yilmaz involved the synthesis of the SAP and the ion-imprinted polymers (IIP) using AA and PEG monomers [71]. The present study investigated the adsorption rate, adsorption capacity, and desorption rate of heavy metal ions, including Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Cr³⁺, Co²⁺, and Fe³⁺, using PEG SAPs. The observed adsorption capacity of heavy metal ions ranged from 31.52 to 396 mg/g. The removal of metal ions from the SAPs was achieved with remarkably high efficiency, reaching up to 97%. The maximum water absorbency of the SAPs at pH = 9 was found to be 2585.3 weight percent (Figure 2) [71].

Figure 2.

SEM image of PEG doped superabsorbent polymer and its swelling in water over time [71].

Superabsorbent hydrogels, characterized by their water-soluble structure, can be transformed into insoluble forms through various cross-linking techniques. Hence, these substances can be classified as hydrophilic polymers, exhibiting insolubility in water while demonstrating notable water absorption capabilities. The performance of absorption capacity is directly influenced by the densities of cross-linking and charge in superabsorbent materials [72]. Due to their porous nature, they are frequently favored for the purpose of retaining heavy metal ions. Due to its notable swelling capacity and user-friendly characteristics, this material finds applications in various fields, including biomedicine [73], drug delivery [74], personal care products [75], batteries and tissue engineering, construction industry [76], food packaging [77], electronics and cables [78], cosmetics [79], and agriculture [80]. These diverse applications highlight the widespread utilization of this material.

In recent times, various hydrogel materials, including poly(acrylic acid), poly(acrylic acid) grafted cellulose, and macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), have been documented as effective agents for the elimination of Cu(II), Cd(II), and Cr(III) in scenarios involving competitive conditions. In their study, Tang et al. successfully produced a hydrogel with an interlocking network (IPN) structure by means of a straightforward two-step aqueous solution polymerization process. The hydrogel was synthesized using a combination of polyacrylate and PEG (PAC/PEG) materials (Figure 3).

Figure 3.

Super absorbent hydrogel synthesized from polyacrylate and polyethylene glycol (PAC/PEG) materials.

In the first step of the polymerization process, acrylic acid (AA) and acrylate (AC) monomers are combined to make a prepolymer called PAC. Subsequently, a copolymerization reaction occurs in step II between the PAC prepolymer and PEG, resulting in the formation of an interpenetrating polymer network (IPN) structure. All the above materials were purchased from Shanghai Chemical Reagents Co., China. The hydrogel that was obtained demonstrated a greater capacity for adsorption when the degree of neutralization was increased, the dosage of AA was increased, and the temperature was decreased. The experimental findings indicated that the quantity of heavy-metal ions adsorbed during the deswelling process was greater in comparison with the adsorption observed during the swelling process [81].

SAPs find extensive application in the production of agricultural fertilizers and wastewater treatment processes. This is primarily attributed to the effective interaction between hydrophilic groups present in the polymer network and specific pollutants such as ammonium nitrogen, heavy metals, and various dyes [82]. Nevertheless, traditional SAPs predominantly consist of synthetic polymers derived from petroleum, which exhibit a high manufacturing expense and limited biodegradability. Copolymers typically consist of anionic and nonionic monomers, with acrylic acid and acrylamide being particularly common examples. Consequently, the formulated SAPs exhibit a predominantly polyanionic nature, thereby frequently falling short of fulfilling the demands imposed by intricate circumstances owing to the uniformity of the ionic composition [83].

In the present context, the synthesis of amphoteric SAPs incorporating hydrophilic groups with both positive and negative charges has emerged as a viable and promising approach for producing SAP. This development has garnered significant attention from numerous researchers. According to Sanjuan and Tran [84], the material demonstrates a net charge that can be either negative, positive, or neutral. Zhao and Su [85] have observed that the material also possesses a distinctive reversible stimulation response. Additionally, Xu [86] has found that the material exhibits a counter-ion extrusion effect and displays superior salt tolerance compared to monoionic polyelectrolytes.

The characteristic features of amphoteric SAPs that contribute to their wide range of applications include the ratio of opposite charges, the degree of dissociation of counterions, intramolecular and intermolecular hydrogen bonding, and coulombic interactions between opposite charges in the network structure. These features have made amphoteric SAPs highly desirable in various fields such as agriculture and horticulture, selective adsorption, bio-separation, fertilizer coatings, controlled drug release, smart materials for biomedical devices, and cardiovascular disease treatment [87].

Waste plastics, composed of diverse synthetic polymers, possess the capacity to undergo chemical modifications and functionalization processes, resulting in the formation of SAPs. Despite the commendable characteristics and extensive range of applications associated with plastics, a substantial quantity of plastic waste is generated annually, constituting approximately 10.6 ± 5.1 weight percent of municipal solid waste [88].

According to Zhou and Fang [89], PE is a predominant constituent of municipal plastic, accounting for approximately 69% of total plastic waste. Due to their nondegradable nature, waste plastics have the potential to cause significant adverse effects on both human and animal populations. The predominant method of disposal for these materials involves landfilling and incineration, often without adhering to appropriate waste management practices. In contrast, limited attention has been given to the functionalization of waste plastics in existing reports. Waste plastics possess the potential for modification via hydrogen extraction, enabling their utilization as skeletal materials for chemical reactions with hydrophilic monomers. This process involves the presence of an initiator and crosslinker, facilitating the preparation of SAPs. In contrast to other recycling methods such as incineration, mechanical recycling, and chemical recycling [88], the production of SAPs offers numerous technological and economic benefits. These include the utilization of mild reaction conditions, simplified operational procedures, cost-effectiveness, and the generation of high-value products. The utilization of plastic waste for the production of SAPs presents a viable and advantageous alternative for the management of plastic waste, owing to its notable economic and ecological advantages.

In their study, Zhang et al. [90] conducted research with the objective of producing SAP by utilizing waste PE film. Initially, a mass of 1.00 g of waste PEG film (which main component is linear low-density polyethylene (LLDPE), which was provided by Shanghai CLEANWRAP plastic Co. Ltd. Shanghai, China) is fully dissolved in a specific quantity of toluene (analytical grade) at a temperature of 93°C. Prior to the reaction, the reactor undergoes a nitrogen purging process in order to eliminate oxygen from the system. Subsequently, different concentrations of benzoyl peroxide (BPO) dissolved in toluene are introduced into the mixture as an initiator, thereby generating radicals. Monomers comprising dimethyl diallyl ammonium chloride (DMDAAC) and partially neutralized acrylic acid (AA) at a mass ratio ranging from 1:16 to 3:16 (m/m) are incrementally introduced into the solution. The density of these monomers falls within the range of 0.16 to 0.19 g/mL. In order to determine the ultimate water/oil ratio, a specific quantity of MBA (N,N′-methylenebisacrylamide) solution is introduced and thoroughly blended for a duration of 25 minutes, resulting in the formation of an emulsion. Ultimately, the resulting products undergo multiple rinses with alcohol and distilled water in order to eliminate any residual monomers and acrylic acid homopolymers. The chemical reagents used in this study were DMDAAC, a 60 weight percent aqueous solution, span 60, and benzoyl peroxide (BPO), all obtained from Sinopharm Chemical Reagent Co. Ltd. In Beijing, China. The acrylic acid (AA) used in this study was obtained from Tianjin Kemiou Chemical Reagent Co. Ltd., located in Tianjin, China. The supplied acrylic acid was chemically pure. N,N′-methylenebisacrylamide (MBA), obtained from the Tianjin Fuchen Chemical Reagent Factory in Tianjin, China, was dissolved in distilled water prior to its utilization.

The quantity of crosslinker is a crucial factor in the development of a highly efficient three-dimensional network structure during the polymerization process. Theoretical studies have indicated that the amount of crosslinker is inversely related to the water absorption capacity of SAP. In this study, a series of innovative amphoteric SAR PE films, consisting of grafted glycidyl methacrylate (g-AA) and dimethyl diallyl ammonium chloride (DMDAAC), were effectively synthesized through reverse emulsion polymerization using waste materials. The amphoteric superabsorbent resins (SARs) exhibited maximum water absorption capacities of 286.3 g/g in distilled water and 213.5 g/g in rainwater. Furthermore, the polymer that was prepared demonstrated a distinct poly amphoteric characteristic across a broad pH spectrum and exhibited the ability to be utilized repeatedly. This research paper introduces a novel, intermediate, and user-friendly methodology for the recycling of plastic waste. Moreover, due to their exceptional properties, the products hold significant potential for utilization in various fields such as agriculture, horticulture, wastewater treatment, civil works, smart materials, and sponge city construction [90].

The majority of prevalent and commercially available superabsorbent materials currently utilized are derived from acrylic acid polymers and copolymers, which are sourced from petroleum and possess the characteristics of being nonrenewable and nonbiodegradable. The escalating apprehensions regarding sustainability and the enduring accessibility of petrochemical feedstocks have generated a growing fascination and potential for the production of superabsorbent materials derived from renewable sources. The integration of bio-based superabsorbent hydrogel production aligns effectively with the biorefinery concept, facilitating the comprehensive utilization of lignocellulosic biomass for the production of biofuels and value-added products. Furthermore, it should be noted that superabsorbent materials derived from natural polymers possess the desirable characteristics of being biodegradable, nontoxic, and biocompatible [70].

In order to address these constraints, researchers have investigated the use of natural polymers, including polysaccharides such as starch, cellulose, chitosan, carrageenan, alginate, and gum arabic, as well as proteins and gelatin cross-linked synthetic polymers, as potential substitutes for petroleum-derived synthetic SAPs.

Choi and colleagues [91] recently published a study introducing a novel sustainable SAP based on poly(itaconic acid) (PIA). Itaconic acid (IA) is an organic acid that is synthesized by the fungus Aspergillus terreus. It is derived from the thermal decomposition of citric acid and possesses a hydrophilic functional group. IA, a bio-derived fermentation feedstock, finds extensive utilization in various industrial sectors such as the manufacturing of synthetic resins, synthetic fibers, plastics, rubbers, surfactants, and oil additives. This is primarily due to its favorable characteristics of being biodegradable and nontoxic. PIA is synthesized through a radial polymerization process, employing IA as the sole monomer. The aforementioned procedure involves the formation of double bonds with IA through the utilization of potassium persulfate (KPS) as an initiator. IA (>99%) monomer and KPS (95%) were purchased from Samchun Pure Chemistry Co., Ltd. (Pyeongtaek, Korea).

The cross-linked PIA superabsorbent (c-PIAS) was then prepared by adding different amounts of PEG diacrylate (PEGDA) as the cross-linking agent to the water-soluble PIA. PEGDA (MW 700 Da) was purchased from Sigma-Aldrich Corporation (St. Louis).

In brief, the production of bio-based c-PIAS was effectively achieved by employing IA as the monomer and PEGDA as the cross-linking agent. The morphology of c-PIAS exhibited two distinct forms, namely a porous mixed structure and a honeycomb structure. According to Choi and Park [91], certain c-PIAS samples that possess a mixed structure exhibit a notable capacity for water absorption. Conversely, c-PIAS samples with a honeycomb structure demonstrate a significant absorption capability when subjected to pressure.

4. Radiation shielding

Radiation shields have been of utmost importance in safeguarding against ionizing radiation in various industrial and medical contexts [92, 93]. The failure to adhere to radiation protection measures poses a significant risk to individuals as exposure to ionizing radiation is considered a highly perilous threat [94]. This risk is applicable regardless of whether the source of radiation stems from the extraction of materials during mining and oil extraction activities or their subsequent transportation and storage. The growing advancements in mining and oil extraction techniques have led to a heightened interest in the development of materials that can effectively prevent radiation leakage. This is crucial in order to safeguard individuals from potential exposure to ionizing radiation [95]. The fundamental and significant factors in radiation therapies and the associated advancement procedures revolve around safeguarding individuals from the detrimental consequences of neutron radiation, as well as the photons discharged by gamma rays and X-rays.

The utilization of polymeric composite materials is progressively growing as a means to mitigate radiation hazards. PE is frequently employed as a material for storing and transporting naturally occurring radioactive substances due to its high hydrogen content, which enables it to effectively absorb neutrons and function as a radiation shield. According to Reis et al. [96], HDPE is considered to be highly suitable for use in packaging and manufacturing various products. High-density HDPE exhibits favorable mechanical characteristics as a hydrocarbon-based polymer. It is cost-effective, possesses high impact resistance, is easily processed, and demonstrates compatibility with a wide range of other polymers [97].

The researchers, Khozemy et al. [98], were able to effectively produce composites that serve as radiation shielding materials. These composites were specifically designed for the purpose of managing naturally occurring radioactive waste. The composites in question were fabricated utilizing a polymer matrix composed of HDPE, which was further strengthened through the incorporation of Pb₂O₃ and Al(OH)₃ materials. The manufacturing procedure entailed the utilization of thermal molding methods. The composites that were prepared demonstrated adjustable attenuation coefficients, which showed a proportional increase with the Al(OH)₃ content present in the sheets. The incorporation of 50% aluminum hydroxide (Al(OH)₃) and 10% lead oxide (Pb₂O₃) into the sample results in a notable enhancement of its gamma-ray shielding capabilities. This improvement is approximately sixfold when compared to the shielding properties of pure HDPE without any reinforcing materials. The increase in the concentration of Al(OH)₃ and the level of irradiation dosage result in a slight improvement in the tensile strength while simultaneously causing a decrease in the elongation. Additionally, it has been observed that the inclusion of Al(OH)₃ composites in HDPE samples results in notable enhancements in thermal stability, thereby yielding favorable and satisfactory outcomes. The composite sheets employed in this research demonstrate cost-effectiveness and exhibit superior efficacy in reducing the impact of ionizing radiation. Moreover, these materials demonstrate significant mechanical characteristics and display advantageous thermal stability, making them suitable for the construction of large containers that are appropriate for storing and transporting naturally occurring radioactive materials.

Aldhuhaibat and colleagues [99] conducted a study to examine the properties of HDPE reinforced composite shields. These shields were enhanced with different metal oxides to assess their effectiveness in attenuating γ-ray radiation, as measured by parameters such as linear attenuation coefficient (μ), mean free path (MFP), half-value layer (HVL), and transmission factor (TF). The researchers discovered that shields coated with PbO demonstrate enhanced attenuation capacity and efficiency in comparison with shields composed of Al₂O₃ and Fe₂O₃. Moreover, the attenuation capacity of the shield is further enhanced by increasing the PbO content. The composite shield consisting of 50% PbO and HDPE demonstrated superior performance across all investigated γ-ray energies, exhibiting the highest value for μ (linear attenuation coefficient) and the smallest values for MFP, HVL (half-value layer), and TF (transmission factor). The composite shield consisting of 50% PbO and HDPE demonstrated superior performance across all investigated γ-ray energies, exhibiting the highest value for the linear attenuation coefficient (μ) and the smallest values for the MFP, HVL, and TVL. The investigation of the relationship between shield material density and various shield types, including pure HDPE and composite shields with varying concentrations of lead oxide (PbO), demonstrated a noticeable increase in the values of μ (a measure of shielding effectiveness). Conversely, the values of MFP, HVL, and TF exhibited a decrease. At the minimum energy level of γ-rays, which is 0.295 MeV, the values of μ are maximized, whereas the values of MFP, HVL, and TVL are minimized. In this study, it was observed that HDPE shields fortified with 0–30% Al and Fe had the lowest values of HVL and efficiency rates of 7.7262 and 18.9230%, respectively. Additionally, it was found that a shield fortified with 0–30% PbO had the lowest HVL values. Demonstrated their core principles and achieved the utmost levels of productivity of 61.4881%. All of the calculations demonstrated a high level of concordance between the experimental and theoretical values. Furthermore, the utilization of PbO as a reinforcing agent resulted in enhancements in both Reinforcement Efficiency Factor (REF) and Displacement of Pb (dPb) calculations. Notably, this improvement was observed to be directly proportional to the concentration of the reinforcement, as observed across all experimental and theoretical energy measurements. Furthermore, it can be observed that the behavior of REF exhibits an inverse relationship to that of dPb as the energy of γ-rays increases. Specifically, the values of REF decrease exponentially, while the values of dPb increase exponentially in response to the escalating γ-ray energy. The utilization of composite shielding comprising 50% PbO/HDPE has been demonstrated as the optimal and highly efficacious method for mitigating the potential hazards associated with radiation exposure.

The study conducted by Malekie et al. [100] aimed to investigate the radiation shielding properties of a composite material composed of bismuth oxide and HDPE. The study focused specifically on the composite’s effectiveness in shielding against gamma rays with an energy of 59.5 keV. To assess these properties, the researchers employed the MCNP, XCOM, and experimental methodologies. The simulation results demonstrated a positive correlation between the weight percentage of bismuth oxide in the polymer matrix and the attenuation coefficient of the composites. This finding aligns well with the data obtained from XCOM. Subsequently, a nanocomposite consisting of 60% Bi₂O₃ was synthesized using the casting technique. The dispersion state of Bi₂O₃ nanoparticles within the polymer matrix was examined using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. The results revealed a semicrystalline behavior, indicating the presence of agglomerations within the polymer matrix. Two techniques, namely the CsI(Tl) scintillation detector and Geiger counter, were employed to measure the attenuation coefficient of the samples against the 241 Am source at an energy of 59.5 keV. The values of μ, μ/ρ, HVL, and TVL quantities for the 60 weight percent composite were determined using various simulation and experimental techniques, demonstrating a strong correlation between the two. The outcomes of the examination conducted on the nanocomposite artifact using a dental X-ray system operating at 60 kV, while imaging an animal jaw revealed that the composite material effectively absorbed the X-rays without causing any detrimental impact on the image’s quality. The findings of this study indicate that the HDPE-Bi₂O₃ nanocomposite possesses the potential to serve as an effective barrier against dental radiography photons and X-rays. It is imperative to underscore the necessity of conducting further comprehensive studies, including precise dosimetry utilizing standard phantoms, in order to employ this nanocomposite, shield for human applications in dental radiography in the future.

The prospective utilization of a polymer with high hydrogen content, combined with a filler material of low atomic mass, exhibits considerable potential as a protective substance, thus offering promising prospects for future applications. The researchers, Harrison et al. [101] demonstrated that the inclusion of boron did not yield a substantial advantage until lower levels of neutron energies were attained. The addition of BN to PE leads to enhanced mechanical characteristics in comparison with unadulterated PE. The implementation of surface modifications on BN particles yields enhanced mechanical properties in comparison to untreated powders. The inclusion of boron nitride (BN) in a composite material leads to an enhancement in the tensile modulus properties as compared to the pure form of the polymer material. The value of the powder surfaces is enhanced through the process of functionalization. The addition of BN powder exhibits negligible impact on the tensile strength in comparison with HDPE. Nevertheless, the incorporation of the coupling agent leads to a more significant enhancement in tensile strength when compared to HDPE.

PE is widely recognized as a material suitable for shielding applications due to its significant hydrogen content. Hydrogen, possessing an atomic number of one, exhibits the most substantial energy dissipation per unit mass. The mean free path of ions in hydrogen is comparatively shorter than that in other materials, resulting in increased fragmentation of heavy ions and a reduced dosage administered. The integration of boron carbide and PE in a composite material has the potential to offer enhanced shielding properties compared to pure PE. The inclusion of filler materials within a PE matrix is expected to enhance the mechanical properties of the resulting composite. A study conducted by Harrison et al. [101] investigated the mechanical properties of BN/PE composites and found that they exhibited enhanced characteristics compared to pure PE.

PE/boron carbide composites play a crucial role in space radiation shielding applications due to their ability to serve as both structural materials and radiation shields, thereby offering distinct advantages. Harrison et al. [102] conducted a study to determine the mechanical and shielding properties of both composites and neat HDPE. Low atomic mass fillers, such as boron, have been found to be advantageous in hydrogen-rich materials as shielding agents. The incorporation of boron carbide into HDPE has been observed to result in enhanced mechanical characteristics. HDPE exhibits a tensile modulus of 588 MPa, which experiences an increase to 943.1 MPa when incorporating 15 vol% of untreated boron carbide powder. These composite materials exhibited superior performance compared to other composites containing boron in various high-energy neutron and proton facilities, demonstrating their effectiveness as shielding materials. The lower density of this material provides it with an advantage over its conventional aluminum counterpart. Furthermore, the merit of PE-based materials lies in their capacity to shield radiation fields without generating long-lived or high-energy gamma-emitting offspring. Ongoing research is being conducted to evaluate the suitability of the material as a low-energy neutron shielding material for the purpose of mitigating neutron spectra within and in the vicinity of nuclear reactors.

The risk of exposure to space radiation poses a significant obstacle in the context of human space exploration. This issue becomes particularly worrisome when considering prolonged exposure in the context of extended space travel, such as during long-duration space flights, low-Earth orbit missions, and expeditions to near-Earth asteroids. In order to tackle this matter, the utilization of multifunctional materials has emerged as a prominent strategy for mitigating the effects of space radiation. Based on the latest NASA Technology Roadmaps, two prominent technology requirements within the top three technology objectives are radiation mitigation for human spaceflight and the development of lightweight and multifunctional materials and structures. The study conducted by Herrman et al. [103] centered on the examination and description of the physical, thermal, and radiation shielding attributes of thermoplastic PE/BN composites. BN composites have been documented as being utilized in applications involving radiation shielding. Nevertheless, the BN fillers employed in these composites exhibited a deficiency in interfacial adhesion with the HDPE matrix, resulting in a restricted enhancement or even deterioration of the physical and radiation shielding properties of HDPE/BN. A base material consisting of HDPE of injection-molding grade was employed. The reinforcement materials chosen for this study were boron carbide and BN, both with particle sizes smaller than 10 m. The suitability of thermoplastic formulations containing PE-BN composites was assessed as a prospective material for radiation shielding in space applications with the aim of safeguarding against galactic cosmic radiation. The utilization of atomic force microscopy (AFM) in the investigation revealed that the blends comprising PE and BN exhibited a satisfactory level of homogeneity when BN concentrations were low. However, as the BN content increased to higher proportions, the uniformity of the blends was observed to decrease. Furthermore, it was noted that the inclusion of BN at a low percentage resulted in a decrease in the compressive strength of these materials, potentially attributable to the lubricating properties of BN. The compressive strength was found to be enhanced with increased levels of BN. The results obtained from the neutron exposure experiments indicate a direct relationship between the initial activity level and the effectiveness of shielding. Specifically, it was observed that a decrease in initial activity corresponds to an increase in shielding effectiveness. Additionally, it has been demonstrated that the quantity of BN within the specimen has an impact on the mass absorption.

Di Fino et al. [104] conducted a study on the International Space Station (ISS) to evaluate the efficacy of PE and Kevlar materials. This evaluation was performed using three detectors of the ALTEA system [105, 106, 107] over a period of time spanning from June 8, 2012 to November 13, 2012. The study was conducted specifically in Express Rack 3 located in the Columbus module of the ISS. These active detectors have the capability to determine the radiation quality parameters in any orbital region. They are identical and can be used simultaneously with one detector serving as the unshielded baseline and the other two detectors measuring radiation with two different amounts of the same material (5 and 10 g/cm²). There is a well-documented similarity in the shielding behavior exhibited by PE and Kevlar. The researchers conducted measurements on the shielding phenomenon, which resulted in a significant reduction of approximately 40% for ions with high atomic numbers. The measurements are presented as ratios relative to the baseline measurements obtained without any shielding material, within the range of 3 to 350 keV/μm for linear energy transfer (LET). The observed decreases in dosage for the 10 g/cm2 shields designed to mitigate high LET radiation (>50 keV/μm, not depicted in the diagram) align with the findings from accelerator measurements (specifically, iron ions at 1 GeV) [4]. In their measurements, it has been observed that the thinner shielding, with a density of 5 g/cm², exhibits approximately a 2% improvement in performance in terms of unit areal density.

Almurayshid et al. [108] conducted an empirical investigation to evaluate the efficacy of different polymer composites in the context of radiation shielding. Compared to lead (Pb), these materials possess the characteristics of being lightweight and nontoxic, rendering them potentially suitable for use as shielding agents in diagnostic radiology applications, particularly in scenarios where low-energy photons are predominantly employed. Their research paper presents an investigation into the fabrication of four composite materials by incorporating a primary component, namely HDPE polymer, with four additional constituents, namely molybdenum, molybdenum carbide, tungsten, or tungsten carbide. The composites obtained were synthesized as 20 disks, with each disk having a thickness of 2 mm. The disks underwent irradiation using a kilovoltage X-ray source with a field size of 1.5 cm². The measurements were conducted to determine the mass attenuation coefficient (μ_m), HVL, MFP, and equivalent atomic number of the disks. It was observed that the addition of additives to HDPE resulted in an improvement in beam attenuation. The composites exhibited higher μm values compared to the pure HDPE polymer. The micrometer (μm) values obtained from the measurements and calculations exhibited a high level of concordance, with an average discrepancy of 5.2%. The experimental investigation involved testing three different additive concentrations, specifically 5, 10, and 15%. The results indicated that the HDPE sample with a 15% concentration exhibited the highest shielding efficiency. The polymer composites containing tungsten (W) and tungsten carbide (WC) demonstrated superior performance in attenuating radiation beams due to their smaller values of half-value layer (HVL) and MFP.

The study conducted by Cinan et al. [109] examined the gamma-ray shielding properties of cross-linked PS-b-PEG when blended with nanostructured selenium dioxide (SeO₂) and BN particles. That study provides an overview of various factors related to radiation shielding, including the μ_m, linear attenuation coefficient (μL), radiation protection efficiency (RPE), HVL, TVL, and MFP. The investigation of the irradiation properties of our nanocomposites was conducted using rays emitted by a 152Eu source within the energy range of 121.780 to 1408.010 keV. That was done utilizing a high-purity germanium (HPGe) detector system, and the data obtained was analyzed using Gamma Vision software. The incorporation of PS-b-PEG copolymer, nanostructured SeO₂, and BN particles resulted in a notable enhancement of the resistance properties of the nanocomposites. Moreover, the nanocomposites with higher additive rates demonstrated superior resistance compared to the other nanocomposites. The observation of the attenuation characteristics of gamma rays in a wide energy range can be achieved by calculating the RPE rates of our polymer-based nanocomposites. The findings of our study demonstrate that the copolymers, when combined with nanostructured SeO₂ and BN nanocomposites, exhibit effective shielding capabilities against gamma rays.

According to the data presented in Figure 4, it can be observed that the highest rates of relative photon emission (RPE) were obtained at an energy level of 121.7817 keV. Furthermore, the maximum rate of RPE recorded in this study was around 22.334%. Upon conducting an analysis of all PS-b-PEG copolymers blended with nanostructured SeO₂ and BN nanocomposites, it was determined that the ingredient with the largest abundance in the nanocomposites was responsible for exhibiting the highest rates of Radiation Protection Efficiency (RPE) and demonstrating optimal behavior in attenuating gamma radiation.

Figure 4.

The RPE rates of the PS-b-PEG copolymers blended with the nanostructured SeO₂ and BN particles under a wide range of gamma irradiation energies.

It is important to acknowledge that an increase in gamma radiation energy leads to a drop in RPE rates. This decrease in RPE rates provides confirmation that our findings align with other computed and experimentally confirmed attenuation parameters, including μ_L, μ_m, HVL, TVL, and MFP.

In their study, Cinan et al. [110] conducted research to investigate the effectiveness of gamma irradiation and the shielding properties on lead oxide (PbO) doped PEG (PS-b-PEG) block copolymers and PS-b-PEG-BN nanocomposite materials. In this study, the investigation focused on the gamma-ray shielding properties of cross-linked PS-b-PEG block copolymers and PS-b-PEG-BN nanocomposites, which were prepared by incorporating varying percentages of PbO. The copolymer was synthesized using emulsion polymerization techniques. The linear-mass attenuation coefficients (LACs-MACs), HVL, MFP, and RPE values of the samples were computed. Through the process of crosschecking the collected data from samples containing both PbO and BN, as well as samples without these substances, an observation was made. It was found that the addition of nano-powders of PbO and BN, in varying weight percentages, to the polymer mixture can serve as an effective shielding material for gamma rays. The incorporation of diverse forms of contributions, such as cement, polymer, and metal oxide, among others, plays a pivotal role in enhancing the hardness, durability, and radiation absorption capabilities of shielding materials. Polymer structures represent a significant category of materials employed in the study of radiation shielding due to their cost-effectiveness and low weight. In Figure 5, the LACs of PbO-doped cross-linked PS-b-PEG block copolymers and PbO-doped PS-b-PEG-BN nanocomposite materials are presented. The LACs were measured at various gamma radiation energies ranging from 121.782 to 1408.006 keV, using ¹⁵³Eu as the radiation source. Additionally, they serve as a basis for various research endeavors involving composites obtained by appending micro- or nano-oxides, among other substances, to explore the theoretical and experimental aspects of radiation attenuation.

Figure 5.

The LACs values of the PbO doped the cross-linked PS-b-PEG block copolymers and the PbO doped the PS-b- PEG-BN nanocomposite materials at different gamma radiation energies (from 121.782 to 1408.006 keV of ¹⁵³Eu).

5. Laser ablation of polyethylene and derivatives and applications

Laser ablation is one of the promising material processing approaches to the surface, internal modification, and nanomaterial generations of different composites from metal to transparent materials (see Figure 6). Over the past two decades, this technique is also well applied to various polymer-based materials for the fabrication of surface structuring from micron to nanoscale. Laser ablation of a polymer target starts with the absorption of incoming photons producing the heating and photoionization of the irradiated area. Subsequently, some polymer material can be torn away from the target as vapors, liquid drops, solid fragments, or as an expanding plasma plume resulting in the surface modification of polymers. Polymer materials are removed by laser ablation technique and could also be used for thin film deposition. In addition, laser ablation of materials in a polymer organic solution opens the door for nanomaterial fabrication with interesting properties. Many factors influence the materials processing performance such as laser parameters (wavelength, power, pulse duration, energy, peak power, etc.), material properties (compositions, absorption, thermal conductivity, thermal expansion coefficient, etc.), laser material interaction parameters (time, focal plane, number of the pulses, etc.), and laser interaction environment (compositions, viscosity, concentration, etc.). Different laser systems and influence factors of the laser interaction to PE and derivatives ablation have been studied in the literature.

Figure 6.

Overview of laser ablation and applications of polyethylene and its derivatives.

The single pulse laser ablation process on PEG 1000 has been investigated by using a time-resolved fast photography technique [111]. The polymer target was ablated by an ArF excimer laser operating at 193 nm wavelength with a pulse duration of 20 ns and an applied fluence of 1.95 J/cm². The interaction area and the process were analyzed with a temporal resolution of 1 ns. They reported that the polymer material ejection from the interacted area is observed in two different time domains: development and removal of plasma (called primer ablation) in the range of 0–50 ns and secondary material ejection between approximately 1 and 100 μs. They assumed that the secondary material ejection is a result of thermal dissociation local melting and vaporization induced by the significant and very fast heating up of the polymer. The number of pulses and the pulse repetition effect on the etch performance of glycol-modified polyethylene terephthalate (PETG) were also investigated [112]. A UV laser operating at 255.3 nm with a pulse duration of 30 ns and a repetition rate from 0.75 to 15 kHz with fluences up to 0.59 J/cm² were tested. They observed that the mean etch rate (μm/pulse) increased slightly with the pulse repetition rate. It is also demonstrated that PETG removal rates (μm/sec) at 15 kHz were therefore at least 15 times faster than at 1 kHz due to the cumulative heating of the sample. The factors of focused spot size, pulse energy, and ablated hole diameter on laser ablation of polyethylene terephthalate (PET) were analyzed by using two different laser systems based on 266 nm nanosecond pulses and 775 nm femtosecond pulses [113]. The thickness of the PET samples played a key role in the estimation of the diameters of the holes machined. In addition, multiple pulse regimes showed different behavior. They demonstrated that smaller holes were achieved with multiple pulses and a lower fluence than with a single pulse with the same total energy. Another comparative study has been also reported in the literature. A Ti: Sapphire laser operating at 790 and 395 nm, and a mixture of both beams were used for the ablation of PE [114]. It has been observed that the etching time of the PE was shorter in the 395 nm case compared to the 790 nm laser. On the other hand, the mixture of the two colors resulted in even deeper an etching performance with the formation of isolated carbon and C∙O and C∙C∙H bonds for all cases. The mechanisms of pulse laser ablation (400 ps pulse duration and 488 nm operation wavelength) of ultra-high-molecular-weight-polyethylene (UHMWPE) are investigated [115]. It is reported that the pulse laser irradiation induced a strong polymer dehydrogenation and molecular emission due to different C_xH_y groups having high kinetic energy and high charge state. In addition, it is also observed dehydrogenated material and carbon-like structures in the crater walls and at the bottom of the crater, respectively. In Ref. [116], a model was proposed to estimate the area and depth of laser ablation. An HDPE was studied by using a laser operating at 1064 nm wavelength with a pulse duration of 10 ns. Different laser powers and the number of pulses allowed to fabricate blind microholes. A model of quantitative area-depth approximation was proposed and confirmed based on gain factors determined by the experimental data with high accuracy.

Laser ablation of polymers is also useful for surface modification and thin film deposition for real-world applications. Different degrees of change to the wettability characteristics of UHMWPE was performed by using different laser operation wavelengths. The laser wavelengths at 1064 and 532 nm showed minimal change in the wettability characteristics but the laser wavelengths at 248 and 308 nm resulted in a marked improvement in the wettability characteristics of the UHMWPE. In particular, the UHMWPE irradiated by 308 nm, after 10 laser shots, reported a linear increase of the polymer wettability [117]. Third harmonics (355 nm) wavelength of solid-state Nd³⁺:YAG laser used for pulse laser wet texturing of flexible PET. A successful texturing of the PET sample was achieved by using a laser fluence of 30 J/cm². The tungsten as a bottom electrode for the photovoltaic device was deposited onto the textured PET surface, and it was shown to enhance optical absorption properties [118]. A Kr–F excimer laser was also applied on the surface modification of the PET samples and investigated the surface tension, surface morphology, and surface chemistry properties of the laser-treated PET samples for biological evaluation. Laser-treated sample presented an enhanced cell behavior, especially cell proliferation and cell adhesion and modified cell morphology [119]. Laser-treated PET surfaces could be considered for biological applications, such as implantable biomaterial. Femtosecond laser pulses were also applied to create a sub-micrometer hole on a thin PET membrane that separated two electrodes. The cell placed onto this hole by negative pressure was punctured using subsequent femtosecond laser exposure to form a hole in the cell membrane. This application opened the way for electrophysiological measurements [120]. In the literature, smooth polyethylene oxide (PEO) thin films with a maximum thickness of 250 nm have been deposited by using a second harmonic (532 nm) Nd³⁺:YAG laser with a pulse duration of 8 ns pulses and a laser fluence of less than 1.6 J/cm². A similar crystalline structure of the formation of PEO thin film compared to the target PEO pellet was confirmed. The molecular weight of the target was affected by the nature of the thin film because the target having a low molecular weight target created more particulate ejection compared with the high molecular weight targets [121].

Laser ablation of materials in liquid media is a simple, one-step, and one of the promising top-down nanomaterials synthesizing techniques. This approach is also well applied for nanoparticle fabrication from PE, as well as in the PE environment. Nanoplastics were fabricated from PET samples by using the laser ablation method to investigate the real environmental nanopollutants effects. The chemical/physical properties and stability of PET nanoparticles in different media were analyzed. The nanoplastics having 100 nm of average dimension presented heterogeneities in size, shape, and weak acid groups on their surface similar to photodegraded PET plastics. No toxic effects were observed in vitro studies in the short term. On the other hand, those nanoparticles were passed through an in vitro Transwell model of the intestinal epithelium [122]. PE solution as a liquid for pulse laser ablation of materials is also an attractive environment for novel nanoparticle generation. The synthetization of gold nanoparticles by using a second harmonic Nd³⁺:YAG ns laser in PE glycol and chitosan for comparative study has been carried out in terms of particle size and optical properties. They indicated that the gold nanoparticles generated in PE were about a glycol environment of 7.49 nm in size, which was the smallest particle size compared to other solutions. The increase in the volume fraction of gold nanoparticles was also improved in PE glycol compared to other solutions. Nonlinear optical properties of the products, such as nonlinear refractive index and nonlinear absorption coefficient, were studied by using the Z-scan technique. The decrease in gold nanoparticles size generated in the PE glycol solution, as well as the increase in the volume fraction directly affected by the nonlinear coefficient compared to other solutions [123]. Nanosecond laser ablation of a graphite target in PEG 200 resulted from the synthetization of fluorescent carbon quantum dots. In this study, the high production efficiency of quantum dots was achieved by using two-step laser ablation (ablation of graphite target and then further ablation of suspension). 1064 nm laser pulse ablation was shown better effective compared to laser ablation with a 355 nm laser pulse. As a result, strong and broadband photoluminescence behavior of quantum dots was fabricated [124]. Vanadium nanoparticles were also synthesized by ablation of the Vanadium target using a 1064 nm laser with a pulse duration of 100 ns in PEG medium. High dispersion stability was presented for vanadium nanoparticles generated in a PEG medium acting as a stabilizing agent compared to vanadium nanoparticles generated in a water medium under similar conditions. The light-to-heat conversion of nanoparticles was then investigated and better performance from vanadium nanoparticles generated in PEG medium in terms of conversion efficiency of incident light-to-heat and thermal stability was obtained compared to nanoparticles generated in water [125]. This type of nanoparticle generated in a PEG medium is a potential candidate for solar-thermal application.

6. Conclusion

PE, a versatile polymer, finds extensive application across diverse industries and various aspects of our everyday existence. PE finds widespread application in various domains, including the following areas: PE is a commonly employed material in the manufacturing process of packaging materials, including but not limited to plastic bags, cling film, plastic bottles, plastic caps, and bags. In this chapter, we evaluated the use of PE and its derivatives as ion-exchange and ion-exchange membranes. We also presented information about the synthesis, exchange capacities, selectivity coefficient of ion-exchangers, and ion-exchange membranes containing cross-linked PE and PEG. The significant advancements in membrane technology and the growing interest in the past decades can be attributed to the extensive potential for practical application of ion-exchange membranes. Ion-exchange membranes are widely utilized in several industrial processes, including electrodialysis, electrodeionization, and electrochemical manufacturing, on a large scale. Simultaneously, ion-exchange membranes find application in electric power generation systems. The majority of commonly used and commercially available superabsorbent materials are derived from acrylic acid polymers and copolymers, which are derived from petroleum and are nonrenewable and nonbiodegradable. The broad applicability of SAPs can be attributed to several distinctive attributes. These include the relative abundance of opposing charges, the extent of counterion dissociation, and the presence of intramolecular and intermolecular hydrogen bonding, as well as the coulombic interactions that occur between opposing charges within the network structure. The beneficial characteristics of SAPs have rendered them highly sought-after in several domains, including agriculture and horticulture, selective adsorption, bio-separation, fertilizer coatings, controlled medication release, smart materials for biomedical devices, and cardiovascular disease treatment. The implementation of effective measures to mitigate the detrimental impact of ionizing radiation on human health and the environment is of utmost importance. The use of polymeric composites as neutron and gamma shields has increased significantly in recent years. Multiple researchers have proposed the construction of multipurpose shields by incorporating metal structures or synthesized minerals into these composites so that they can be utilized in photon fields. Boron-containing PE composites can be utilized as effective neutron shields due to their high neutron absorption cross section. The integration of many types of contributions, including cement, polymer, metal oxide, and others, significantly contributes to the improvement of the hardness, durability, and radiation absorption properties of shielding materials. Polymer structures are widely utilized in the field of radiation shielding because of their cost-effectiveness and lightweight nature, making them a prominent category of materials in this area of study. Laser ablation is effectively applied to a variety of polymer-based materials for micron- to nanometer-scale surface structuring. Ablation of a polymer target by laser begins with the absorption of incoming photons, which heats and ionizes the irradiated area. Some polymer material can then be torn away from the target as vapors, liquid droplets, solid fragments, or an expanding plasma plume, resulting in surface modification of polymers.

Acknowledgments

The authors thank to Karadeniz Technical University for their support. In addition, the authors also would like to express gratitude to Bilkent University UNAM for their kind hospitality. The authors would like to thank to İbrahim ERDEMOGLU for their support.