Bast Fiber Textiles Addressed Improvement of Human Life

Abstract

Cannabis sativa L. and Linum usitatissimum L. belong to fibrous plant family delivering textile fibers located in their bast of stalk. This chapter covers discussion about flax and hemp fibers properties and processing based on authors’ finding and available literature. The authors will present research on flax and hemp fibers bioactivity in relationship with their chemical composition, which is strongly related to the selected method of fiber processing, including methods of fiber extraction in light of their effect on fibers antioxidant and antibacterial activity. Human-ecological features of linen/hemp textiles, including clothing effect on human physiology, are described. The case study of functional clothing preparation based on the bioactivity of bast fibers will be presented. This chapter delivers knowledge about complex factors of human-ecological performance of flax and hemp, which have a significant effect on the improvement of human life, including comfort, well-being, and health-supporting performance. The environmental approach of bast fibers in terms of contribution to green planet protection is shortly discussed. Collected literature and authors’ findings allowed to prove the positive effect of bast fibers textiles on the improvement of human life in terms of everyday wearing of clothing as well from the viewpoint of environmental impact, which is in line with the European Green Deal strategy.

1. Introduction

Cannabis sativa L. and Linum usitatissimum L. belong to fibrous plant family containing fibers occurring as bast of the stalk. Both the fibrous plants have gained importance in the face of bioeconomy development in the whole world resulting from pro-ecological character of the flax/hemp value chains as well as a growing preference for natural raw materials, which are desired for bioproduct manufacture in many sectors.

Observed climate change and environmental degradation impose taking measures that will protect the globe for future generations [1]. The European Green Deal (EGD) set up three main objectives to counteract negative phenomenon:

• no net emissions of greenhouse gases by 2050,

• economic growth decoupled from resource use,

• no person and no place left behind.

One of the assumptions of the European Green Deal is the improvement of the well-being and health of citizens by providing:

• fresh air, clean water, healthy soil, and biodiversity,

• longer lasting products that can be repaired, recycled, and reused.

C. sativa L. and L. usitatissimum L. plants, delivered by them raw materials as well as flax/hemp value chains and bast-fiber-based bioproducts are fully in line with the EGD measures. Their impact on environment and agriculture is discussed in many scientific articles [2, 3, 4, 5, 6].

The hemp cultivation ensures positive impact on preserving biodiversity, improvement of soil quality, and dredging of heavy metals from the ground and, from the other side, supports cleaning of air by the absorption of CO₂ from atmosphere. Hemp is a yearling fast growing plant with well-developed leaves system, which results in that one season of hemp cultivation causes absorption about 10 tons of CO₂ from the air. Hemp is resistant to drought; due to a long-root system, dense hemp cultivation causes effective blocking of weed growing, which means significantly less consumption of water and pesticides in comparison to cotton. The environmental approach to flax/linen processes based on Life cycle assessment (LCA) study for linen shirt production confirms that the impacts of the linen shirt are up to seven times smaller than the impacts of the cotton shirt in terms of the most relevant environmental indicators, such as the freshwater aquatic ecotoxicity potential or water consumption. In the case of the global warming potential or the primary energy consumption, the environmental impacts of the linen shirt production are either equivalent to those of the cotton shirt or 10–15% higher [7].

Reports on linen/hemp textile bioactivity and its effect on human in terms of the well-being and health of wearer are very limited in the available literature.

The goal of this chapter is to provide knowledge covering a new approach to flax/hemp fibers regarding their potential to give new properties of clothing, which are able to ensure optimal environment for human body and improve health and quality of life. The properties of the textiles are determined by carefully selected fibrous plant variety and fiber processing suitable to final application.

This chapter covers discussion about new approach to the flax and hemp fibers taking into account their features and potential to have a positive impact on human life, based on authors’ finding and other available literature.

The authors introduce multiperspective meaning of the term “improvement of human life” to demonstrate environmental and human-ecological performance of flax/hemp fibers.

The discussed textile plant raw materials have positive impact on the following:

1. environment—ensuring contribution to striving toward keeping green planet and healthy life for current and future generation,

   • hemp and flax cultivation protects agriculture areas against loss of biodiversity, which is important for limitation of greenhouse gasses emission,

   • hemp improves the productivity of the soil, removes heavy metals, and can be used for soil remediation and reclamation at industrial area,

   • 1 ha of hemp plantation absorbs about 10 tons of CO₂ from atmosphere every year,

   • hemp and flax have potential to cascade the use of the whole biomass delivering war materials to different sectors of economy, according to strategy “zero waste,”

   • fibrous plants deliver raw materials for production of bioproducts giving possibility to replace nonrenewable raw materials, e.g., construction, plastics, textiles, with natural ones

   • hemp and flax fibers are renewable and biodegradable;

   • the pursuit of plastic elimination in many sectors, including everyday life contribute to the reduction of greenhouse gasses emissions and, consequently, decarbonization,

2. multifaced human-ecological performance—linen and hemp textiles based on their inherent properties ensure comfort, well-being, and health-supporting properties for users target improving of everyday life.

Both the aspects of environmental and human-ecological performance of flax and hemp have to be identified as complex factors, which have a significant effect on the improvement of human life.

2. Characteristic of bast fibers: structure and chemical composition

Flax and hemp are the most popular bast fibers, which can be used for textile purpose, including apparels. The lignocellulosic fibers are delivered by yearling plants with potential of multiple applications.

The structure of stem of flax and hemp is very similar; fibers are created as concentric rings around lumen and xylem in the whole length of stem parallel to the stem axis. Figure 1 shows the cross section of flax and hemp stem [8, 9].

Figure 1.

Structure of flax and hemp stem. (a) Cross section of stem. (b) Fiber bundle.

The cellulosic structure inside the secondary cell wall of fiber is schematically presented in Figure 2.

Figure 2.

Schematic depiction of the microscopic structure of an elementary flax fiber showing the cellulosic structure inside the secondary cell wall (figure redrawn from [10]).

Flax and hemp fibers occur in form of bundle called technical fibers containing elementary fibers glued by pectin and lignin as well as naturally connected together due to their arborescent structure (Figure 3).

Figure 3.

Real and graphical image of naturally arborescent structure of flax/hemp fibers (based on [11, 12]).

2.1 Chemical composition

Bast fibers contain cellulose, lignin, hemicellulose, pectin, waxes, and fats in their chemical composition. The schematic image of the chemical components distribution in the cell wall of the fiber is presented in Figure 4. The figure illustrates schematically in which way the chemical components of bast fibers are distributed in the fiber structure.

Figure 4.

Schematic image of the section of a hemp cell wall [13].

The share of the chemical components depends on the fibrous plant variety and the applied method of fiber extraction. From this reason, different values of the cellulose, lignin, pectin, and hemicellulose waxes are given by different authors in their scientific articles [14, 15, 16, 17, 18].

The diversification of fiber chemical composition [19] resulting from fibrous plan variety, applied method of retting, fiber extraction, and subsequent stages of processes is presented in Table 1.

Degumming method	Variety	Content of:
		Waxes and fats		Pectin		Lignin		Celullose		Hemicelullose
		%	SD	%	SD	%	SD	%	SD	%	SD
HEMP
Water retting	Beniko	0.23	0.01	1.47	0.09	2.81	0.29	71.31	1.32	15.03	0.02
	Wojko	0.24	0.04	0.67	0.02	3.02	0.31	72.53	0.11	16.67	0.24
	Tygra	0.25	0.04	0.56	0.00	2.78	0.28	70.79	0.13	15.00	0.28
	Białobrzeskie	0.34	0.02	0.67	0.02	2.38	0.22	72.03	0.22	14.37	0.29
Decortication		0.47	0.02	2.00	0.09	5.55	0.17	66.02	0.46	21.25	0.05
Dew retting		0.56	0.14	3.68	0.19	4.31	0.04	66.16	0.48	21.72	0.12
Water retting	Białobrzeskie	0.34	0.02	0.67	0.02	2.38	0.22	72.03	0.22	14.37	0.29
Osmotic degumming		0.44	0.04	2.82	0.22	4.03	0.09	67.81	0.52	16.29	0.03
FLAX
Decortication		1.26	0.00	4.62	0.16	4.00	0.16	68.89	1.91	29.35	0.16
Wet degumming +ultrasound	Modran	0.69	0.07	4.41	0.50	4.20	0.16	75.54	1.18	19.62	0.15
Cottonization		0.97	0.10	4.72	0.39	4.26	0.15	73.51	0.98	16.44	0.23
Decortication		1.47	0.07	4.11	0.38	8.60	0.30	64.57	0.85	29.38	0.08
Wet degumming +ultrasound	NIKE	0.76	0.00	3.56	0.27	4.46	0.48	77.44	1.58	16.43	0.25
Cottonization		0.95	0.05	2.39	0.22	4.87	0.51	74.25	0.20	13.84	0.06
Decortication		1.47	0.07	4.11	0.38	8.60	0.30	64.57	0.85	29.38	0.08
Wet degumming +ultrasound	B14 Iung	1.33	0.01	5.43	0.28	6.69	0.48	75.04	0.46	23.92	0.02
Cottonization		1.72	0.09	3.57	0.23	6.10	0.01	72.20	0.47	20.41	0.09

Table 1.

Chemical composition of fibers coming from different varieties of flax controlled in sequence stages of fiber processing; different varieties of hemp extracted with use of dew retting as well as hemp fiber Białobrzeskie variety obtained by different methods of fiber extraction: Decortication, osmotically degumming, and water retting [19].

The cultivar of fibrous plants, the method of plant growing, and the method of fiber extraction have to be selected taking into account the obtaining of the fiber with chemical composition suitable for textile purpose. The high cellulose content gives softness to the fiber and ensures efficient spinnability in opposite to lignin and pectin. Their big share in the fiber results in low fiber quality, e.g., high stiffness and high linear density coming from inefficient fiber separation, which makes the spin process difficult.

3. Bast fiber processes

Flax/hemp fiber extraction from the stem is strongly connected to the retting process, which is usually a microbiological process that uses bacteria and fungi strains applied in order to degrade pectin and lignin, remove woody part of the stalk, and divide the technical bundles to smaller fiber complexes. There are several retting methods: water, dew, chemical, enzymatic, and physical retting. The use of the three last listed methods is limited to small application; these methods have not been used in large industrial scale yet.

The traditional water retting process delivers the best quality of long fibers characterizing by high cellulose content and low lignin and pectin share resulting in low fiber linear density, good mechanical properties, and good spinnability. Water retting used to be the most recommended process for bast fiber dedicated to textile production. Nevertheless, owing to the generation of large amounts of wastewater and high pollution of soil and air, this method has been abandoned in Europe and many other countries in the 1960s [20, 21, 22].

The second retting method delivering good quality of long fibers is dew retting; nevertheless, the process effectiveness and quality of the fibers are not stabile because it depends on weather conditions prevailing in time of the stalk remaining on the field.

The method of fiber extraction, which allows one to avoid the retting process, is the decortication of raw straw collected when the plants reach proper fiber maturity. Decortication is a mechanical process giving one type of insufficiently dividing fibers with high impurities content.

The method of flax/hemp fiber extraction determines further technological chain of fiber processing and spinning. The simplified schema of value chains of bast-fiber-based textile for both the methods of fiber extraction, e.g., with the use of retting and with application of decortication, is presented in Figure 5.

Figure 5.

Simplified value chain of hemp/flax textile product [own elaboration].

Flax/hemp stalks after retting are mechanically breaking and scutching to separate fibers from the woody part of the plant and dividing big complexes of fibers to smaller ones. The processes are efficient due to the decomposition of noncellulose components made by bacteria and fungi activity during retting. As a result of scutching, long fibers and scutched tow are produced. Long fibers must be mechanically cleaned and straighten as well as laid parallelly toward each other with the use of hackling machine dedicated only to bast fibers processing. The hackling process delivers sliver of long fibers and mass of short fibers, e.g., hackling tow. Both types of fibers are spun with application of linen spinning system, long fibers with the use of wet spinning, and short fibers by wet or dry spinning.

Second value chain determined for decorticated fibers allowing avoid of retting has to employ the wet degummed process to remove lignin, pectin, and partially hemicellulose in order to make it possible to divide the bast fibers for elementary ones. Using this system, only one type of fibers is produced; it is not possible to obtain long and separately short fibers. Degummed decorticated fibers are cottonized to make the fibers suitable for spinning with the use of the cotton spinning system [23].

The yarn prepared by using the cotton spinning system, including decortication, and the linen spinning system can be used for textile purpose.

4. Bioactivity of bast fibers

4.1 Antioxidant activity

Flax and hemp fibers apart from the main components as cellulose, hemicellulose, pectin, lignin, fats, and waxes contain in their chemical composition phenolic acids, which are natural antioxidants [24]. Based on an effectively scavenging chain reaction and deleterious radicals as well as suppressing radiation-induced oxidative reactions, phenolic acids serve for preserving the physiological integrity of plant cells exposed to both air and impinging ultraviolet (UV) radiation [25].

The study described in [19] confirmed the diversified presence of ferulic, p-coumaric, syringic acids and small amounts of sinapinic acid in the chemical composition of flax and hemp fibers. The differences resulted from various fibrous plant varieties and the method of fiber extraction, which have effect on their chemical composition. Syringic acid naturally occurring in O-methylated phenolic acid shows high antioxidant and antibacterial activity and can be enzymatically degraded by some bacteria as a source of methane or methanol [26]. As is visible in Table 2, the decorticated fibers of hemp Bialobrzeskie as well as Modran and B14 flax varieties show the highest content of syringic acid. The lower share in retted fibers results from the fact that syringic acid can be degraded during the biological retting process.

Degumming method	Variety	Content of acids:
		Syringic [mg/100 g]		Sinapinic [mg/100 g]		p-coumaric [mg/100 g]		Ferulic [mg/100 g]
		Result	±SD	Result	±SD	Result	±SD	Result	±SD
HEMP
Water retting	Beniko	0.031^a	0.001	-*^a	—	0.722^a,b	0.019	-*^a	—
	Wojko	0.046	0.001	0.048	0.002	0.741^a	0.006	0.027^a	0.001
	Tygra	0.036	0.001	0.100	0.003	0.695^b	0.034	0.572	0.031
	Białobrzeskie	0.033^a	0.001	-*^a	—	0.024	0.006	-*^a	—
Decortication		0.224	0.011	0.672	0.023	0.746	0.008	2.082	0.036
Dew retting		0.079	0.003	-*^a	—	0.717	0.008	0.039^a	0.004
Water retting	Białobrzeskie	0.033	0.001	-*a	—	0.024	0.006	-*^a	—
Osmotic degumming		0.094	0.003	-*^a	—	1.111	0.011	0.625	0.009
FLAX
Decortication		0.235	0.008	-*^a	—	0.995	0.024	5.749	0.159
Wet degumming + ultrasound	Modran	-*	—	-*^a	—	-*^a	—	0.041	0.002
Cottonization		0.035	0.002	-*^a	—	-*^a	—	1.206	0.053
Decortication		-*^a	—	-*^a	—	-*^a	—	1.485	0.034
Wet degumming + ultrasound	NIKE	-*^a	—	-*	—	-*^a	—	0.054	0.001
Cottonization		-*^a	—	-*^a	—	-*^a	—	1.035	0.020
Decortication		0.125	0.060	-*^a	—	0.904	0.009	3.146	0.106
Wet degumming + ultrasound	B14 IUNG	0.052^a	0.002	-*^a	—	0.027	0.008	2.525	0.106
Cottonization		0.040^a	0.001	-*^a	—	0.756	0.034	1.736	0.045

Table 2.

Acid content in the flax and hemp fiber. Results are expressed as mean ± standard deviation (SD), n = 4. Lowercase letters indicate significant differences at p ≤ 0.05 according to the Tukay’s HSD test [19].

-* not identified.

a and b represent the groups for which the mean values do not differ statistically at the assumed significance level. The mean values labeled with the same letter (a or b) do not differ statistically at (α = 0.05).

Sinapinic acid (3,5-dimethoxy-4-hydroxycinnamic acid) exhibits antioxidant, anti-inflammatory, anticancer, antimutagenic, antiglycemic, neuroprotective, and antibacterial activities [27]. Sinapinic acid occurs only in hemp fibers; the highest amount was detected in the decorticated Bialobrzeskie hemp, as well as in the water-retted Wojko and Tygra hemp.

Coumaric and ferulic acids are the main hydroxycinnamic acids in flax [28]. p-coumaric acid is mainly a plant metabolite, which exhibits antioxidant and anti-inflammatory properties. It also shows bactericidal activity by damaging bacterial cell membrane and by interacting with bacterial DNA.

Ferulic acid, together with dihydroferulic acid, is a component of lignocellulose, serving to crosslink the lignin and polysaccharides, thereby conferring rigidity to the cell walls [29]. It is an intermediate in the synthesis of monolignols, the monomers of lignin, and is also used for the synthesis of lignans. Ferulic acid shows antioxidant and anti-inflammatory properties and is able to suppress UV-radiation-induced oxidative reductions, which has a negative effect on the skin.

Ferulic acid is easily soluble in water and can be easily removed from the fibers during the retting process; however, coumaric acid is poorly soluble in water, and its removal could be only partial. Among all types of tested flax and hemp fibers, almost all the decorticated fibers contained the highest amount of p-coumaric and ferulic acids because decortication is an entirely dry mechanical process.

Because the flax and hemp fibers contain phenolic acids in their chemical composition, they show antioxidant activity, which is presented in Table 3. The fiber antioxidant activity depends on the type and variety of fibrous plant as well as on the method of fiber extraction [30]. The highest value of ferric reducing antioxidant power (FRAP) and value of 2,2,2-diphenyl-1-picrylhydrazyl (DPPH radical) scavenging activity illustrating antioxidant activity of the fibers were found in all types of fibers after decortication because the fibers contain the largest amount of phenolic acids.

Degumming method	Variety	FRAP [μmol/L]		Inhibition of DPPH [%]
		Result	±SD	Result	±SD
HEMP
Water retting	Beniko	140.34	4.75	11.30^a	0.92
	Wojko	156.75	2.31	10.04^a	0.49
	Tygra	165.76	1.62	32.55	0.32
	Białobrzeskie	76.62	1.33	3.09	0.18
Decortication		230.22	1.55	18.03	0.63
Dew retting		124.09	1.93	5.31	0.25
Water retting	Białobrzeskie	76.62	1.33	3.09^a	0.18
Osmotic degumming		93.71	0.69	3.94^a	0.19
FLAX
Decortication		523.00	2.08	33.85	0.17
Wet degumming + ultrasound	Modran	129.45	1.28	5.80	0.14
Cottonization		70.69	2.31	3.29	0.24
Decortication		519.75	2.69	29.76	0.15
Wet degumming + ultrasound	NIKE	140.79	1.16	7.64	0.16
Cottonization		78.84	1.59	5.10	0.36
Decortication		485.84	2.11	37.71	0.14
Wet degumming + ultrasound	B14 Iung	195.79	2.23	11.05	0.11
Cottonization		119.42	4.55	6.82	0.23

Table 3.

The antioxidative activity of different varieties of bast fibers depending on the extraction method. Results are expressed as mean wf standard deviation (SD), n = 3. Lowercase letters indicate significant differences at p ≤ 0.05 according to the Tukay’s HSD test [19].

a represents the group for which the mean values do not differ statistically at the assumed significance level. The mean values labeled with the same letter (a) do not differ statistically at (α = 0,05).

4.2 Antibacterial activity

The tests of antibacterial properties of flax fibers were conducted with a fluorescent method using strains of the clinical bacteria Staphylococcus aureus isolated from ill people [31].

Test conditions:

• Bacterial suspension density: 0.5 McF,

• Incubation conditions: temperature—37°C, time—90 min.

S. aureus belongs to the most common etiological factors of inflammation in surgical places. The evaluation of bacteria viability was performed using the Bacterial Viability Kit (Molecular Probes).

The images presented in Figures 6 and 7 show the fibers and strains of the clinical bacteria S. aureus isolated from ill people after 90 minutes of incubation. The orange particles on the fiber surface illustrate killed bacteria. It is visible that killed bacteria are located only in direct contact with the fibers.

Figure 6.

Dew retted flax fibers activity toward staphylococcus aureus bacteria.

Figure 7.

Dew retted hemp fibers activity toward staphylococcus aureus bacteria.

The study [31] on the antibacterial activity of flax covered five varieties: Artemida, Modran, Sara Nike, and Luna. The extracted fibers with use of dew retting or water retting method were tested in order to evaluate their ability to reduce colonies of S. aureus bacteria. The results confirmed that the fiber antibacterial capacity is strongly related to plant variety and the applied extraction method, which have effect on fibers chemical composition, mainly content of lignin cross-linked with phenolic compounds. Percentage differences in the antibacterial capacity of all types of flax fibers are shown in Figure 8.

Figure 8.

Comparison of antibacterial capacity of flax fibers.

Dew-retted flax fibers coming from all tested plant varieties showed stronger capacity to reduce S. aureus bacterial colonies than water-retted fibers. This resulted from the fact that some types of phenolic acids, for example, ferulic acid, are water soluble and have been removed during the water-retting process.

4.3 Antimicrobial modification of bast fibers

4.3.1 Genetic engineering

In order to improve antibacterial properties of flax fibers, researchers applied genetic engineering to modify plant DNA [32]. Transgenic flax plants overproducing compounds from phenylpropanoid pathway accumulate phenolic derivatives of potential antioxidative and, thus, antimicrobial activity. The researchers showed that the extract alkali hydrolyzed seedcake had antibacterial activity, which might be useful as a prophylactic against bacterial infection.

Although the GMO plant modification is not allowed in Europe due to the strategy “Europe free from GMO,” studies on fibrous plant genetic engineering are very limited.

4.3.2 Chemical modification

The way to obtain stronger antibacterial properties of bast fibers is the chemical modification of linear or flat textiles. Flax and hemp as cellulosic fibers are characterized with high reactivity due to containing hydroxy group in compounds in their chemical composition.

Racu conducted study on the application of grafting of monochlorotriazinyl-β-cyclodextrin on hemp fiber stream at the time of wet spinning. Four compounds, e.g., ferulic acid, caffeic acid, ethyl ferulate, and allantoin, have been included into the cavities of monochlorotriazinyl-β-cyclodextrin and grafted on hemp fibers. Obtained yarn showed that the method allowed for a significant modification of Sano Genetics properties of the hemp fibers [33].

The application of silver in shape of nanoparticles is the most common method to functionalize different textile materials, including natural fibers. Research on the functionalization of the scoured flax fibers by the insertion of silver nanoparticles was conducted with the use of two different methods: first where Ag + was reduced by using the functional groups of flax in the internal reduction, and second where trisodium citrate was used as an external reducing agent in the external reduction method [34]. The modified scoured flax fibers with silver nanoparticles showed very good barrier properties against UV radiation and excellent antibacterial activity.

A good example of nanosilver application for hemp fiber to make strong antibacterial activity is the use of selective 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation, i.e., oxidation with sodium hypochlorite, catalytic amount of sodium bromide, and the 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO), followed by silver sorption from aqueous silver nitrate solution, described by Milanović et al. [35]. The introduced hydrophilic carboxyl in hemp fibers caused by TEMPO-mediated oxidation influenced increased silver sorption and, in consequence, gave efficient antibacterial activity. The TEMPO-oxidized hemp fibers with absorbed silver showed good antibacterial activity against the tested bacterium strains: S. aureus and Escherichia coli, and the fungus Candida. albicans.

The new method of improving of antibacterial activity of hemp fibers has been developed by Chang [36]. The research group developed method of grafting of hemp fiber with the use of quaternary ammonium groups (HF–GTA) prepared by alkalization, oxidation, amination, and quaternization multistage reactions, whereby the grafting reaction mainly takes place on the cellulose and hemicellulose hydroxyl groups, without negative effect on fibrous morphology, thermal stability, and hygroscopicity. This method gives good antibacterial activity of hemp fiber against bacteria strains E. coli and S. aureus. The obtained barrier properties are characterized by good washing resistance.

5. Well-being and comfort

Physiological comfort determined by skin parameters, such as temperature and moisture, is affected by raw materials as well as clothing design and depends particularly on the suitability of worn type of clothing to the level of physical activity of user and ambient climatic conditions.

Hemp and flax fibers show high ability to moisture sorption from ambient air. The hygroscopicity of lignocellulosic fibers depends on the relative humidity of air, which is shown in Table 4. The fibers can absorb more moisture in conditions of higher relative humidity of air, which means, in practice, that the linen/hemp clothing easily absorbs sweat produced by the human body. In the case of conditions of everyday life and moderate physical effort, the clothing ensures optimal comfort to the wearer, allowing easy skin breathing and air exchange from the area of skin clothing to outside. In the case of high physical effort, doing sports, when the intensity of sweating is high, the T-shirt made of cellulosic raw material becomes uncomfortable due to feeling of wet touch. Linen/hemp clothing should be dedicated to everyday life, indoor and outdoor work, leisure, tourism, and other activities with low and moderate effort, when the garment ensures optimal comfort to the human body [37].

Fiber	Moisture content in condition of different relative humidity of air [%]
	30	40	50	60	70	100
Flax	7.5	8.3	9.1	9.9	10.7	23
Hemp	8.0	8.7	9.4	10.1	10.8	24

Table 4.

Effect of relative air humidity on the hygroscopicity of selected bast fibers [17].

The comparative study on comfort parameters of linen and linen/polyethersulfone (PES) clothing during moderate physical exercise was described by Zimniewska [38]. Tested shirts and trousers were prepared from linen and polyester fiber in different composition of the raw materials; share of linen in the blend with PES increased by 25% in each following clothing sample. The fabrics were characterized by the similar density of threads; linen and PES yarns produced to this experiment have similar linear density.

Values of the parameters that affected the comfort of clothing are presented in Figures 9–12.

Figure 9.

Hygroscopicity of linen/PES fabrics tested in 65% and 100% relative humidity of air (based on [38]).

Figure 10.

Time needed to drop water sorption by tested linen/PES fabrics (based on [38]).

Figure 11.

Air permeability of linen/PES fabrics with different share of both types fiber (based on [38]).

Figure 12.

Surface resistance of linen/PES fabrics with different share of both types fiber (based on [38]).

The fabric hygroscopicity increased with increasing of the share of linen in the blends linen/PES; similarly, the time needed to drop water sorption is longer in the case of bigger PES content in the blend. The linen fabric showed the biggest value of air permeability; the lowest one was observed for 100% PES fabric. The evaluation of moisture of back skin of clothing users during 5 hours of experiment was conducted in order to assess the comfort. During the experiment, volunteers did not perform any physical activity. Results of the experiment are presented in Figure 13.

Figure 13.

The moisture of back skin under tested clothes during 5 hours of experiment (Grant 1000 series squirrel – Operating instruction) [38].

The results proved that the skin moisture was the lowest in case of wearing the clothing made of 100% linen; however, the biggest increasing of moisture was observed when PES clothing was worn.

Bast fiber does not gather electrostatic charges on their surface, which results in their high ability of moisture sorption. The values of electrostatic potential of the tested linen/PES fabrics are presented in Figure 14, where the highest value observed for PES fabric decreased when linen share in the blends increased. The presence of electrostatic charges on the synthetic clothing surface results in some kind of skin and mental irritation of garment users.

Figure 14.

The electrostatic potential on the surface of tested fabrics [39].

6. Positive effect on the human body

Clothing covering the body of the user in the conditions of daily life affects their physiological parameters. The clothing made of bast fibers or made from blend bast fibers/synthetic fibers with high share of natural fibers provides the optimal comfort for users and affects some physiological parameters of the human body.

6.1 Muscle tension and fatigue tendency

The human skin parameters that determine the comfort during clothing wearing in ambient climatic conditions and given level of physical activity are strongly related to well-being and can affect tendency to tiredness [38, 39].

The study on the monitoring of shoulder muscle tension of volunteers wearing linen/PES clothing with different shares of both components allowed identifying the phenomenon of clothing influence on electromyographic parameters of the muscles [38]. Examples of global electromyographic records taken at resting state from a volunteer wearing 100% linen clothing (a), 100% linen clothing double layers (b), 50% linen 50% PES clothing (c), and 100% PES are presented in Figure 15. The results of the tests proved that polyester clothing can change muscle electromyography (EMG) records in the range of amplitude and frequency after 5 hours of covering on the body with this kind of apparel, which indicates the occurrence of desynchronization of motor units. In the case of wearing linen clothing, such a phenomenon did not occur. The PES clothing gathered electrostatic charges on its surface causing increase in the mean value of frequency of motor units in the resting state. More intensive sweating of volunteers’ body under the influence of PES clothing caused changes in the EMG amplitude in the resting state and amplitude and frequency during voluntary movement. The threshold value of polyester fiber share in blend with linen fiber is 25%. The clothing made of 100% linen fabric or 75% linen/25% PES did not cause the desynchronization of motor units in healthy muscles and provided optimal comfort of apparel use. Changes in the activity of the motor units of muscles found during the study proved that the polyester clothing can cause increase of tendency toward general fatigue of people wearing the clothing.

Figure 15.

Examples of global electromyographic records taken at resting state from a volunteer wearing: 100% linen clothing (a), 100% linen clothing double layers (b), 50% linen 50% PES clothing (c), and 100% PES (d) [39].

6.2 Oxidative stress

Study on clothing influence on some parameters of human physiology covered the experiment on oxidative stress affected by clothing made of different raw materials [37]. The experiment was done with volunteers wearing linen and then PES clothing in given climatic conditions during an 8-hour rest period, 20-minute moderate physical activity at a level of 75 W, on a stationary bike and the period of returning to baseline. One of the ways to test the ability of the organism to defense itself against the reactive oxygen species is to determine the so-called total antioxidant status (TAS). This parameter informs about the total ability of tissues to neutralize exactly determined amount of reactive oxygen species. The TAS was tested based on blood analysis after each stage of the volunteers’ activity.

The results of the TAS test are shown in Figure 16. The lower level of total antioxidative status in individuals wearing polyester clothing indicated that, probably, this is an effect of increased production of reactive oxygen species, which are responsible for the oxidative stress. The phenomena observed during conducted tests confirmed the stipulations that the wear made of linen—a natural fiber—not only guarantees a comfort, but may also have a positive effect on users’ health. The clothes made from polyester fibers can have an unfavorable effect on human organism.

Figure 16.

The values of total antioxidant status (TAS) in volunteers wearing linen and PES clothing [40].

These TAS changes tested in conditions of increased sweating, i.e., during exercise, were statistically significant. The results of the research resulted from the following phenomena accompanying of polyester clothing:

• accumulation of electrostatic charges on the surface,

• low permeability,

• low hygroscopicity,

• cause of sweating increase,

• cause increase of body temperature.

6.3 UV barrier

Garment barrier properties against ultraviolet radiation are mainly determined by the structure and thickness of fabric or knitted fabric used for clothing preparation. High fabric density and minimalized porosity play the most important role to block UV rays transitioning through the fabric and make it impossible to touch the skin of the wearer.

Even in the dense structure of fabrics and proper thickness to make mechanical barrier against radiation, the clothing does not always ensure safety for wearers in conditions of intensive solar radiation.

Bast fibers contain in their chemical composition lignin and phenolic acids, including ferulic acid, with ability to absorb ultraviolet rays. The values of ultraviolet protection factor (UPF) of tested samples of linen fabrics characterized by different mesh/hollows content in their structure are shown in Figure 17 [41]. Clothing made of bast fibers with proper parameters of fabric structure offers very good UV barrier properties—guarantee safety and optimal comfort for users under conditions of solar radiation.

Figure 17.

“Mesh” size and UPF of 100% flax fabrics [41].

In case of using the garment in extremely high UV index area, the inherent protective properties of bast fibers can be supported by the application of UV absorbers, for example, by nanolignin coating, which is the most ecological method of fabric modification [42, 43].

7. Bioactive bast fiber textile products

7.1 Clothing as a supplement of skin disease treatment

The bast fibers showing inherent antibacterial and antioxidant activity and properties guaranteeing optimal comfort of clothing are suitable raw materials dedicated to functional textile manufacture. One of the examples of flax fiber functional textile is clothing, which acts as a supplement of dressing addressed the treatment of dermatological diseases [44]. The clothing was made of combination of two raw materials: linen for active part of clothing and organic cotton for other clothing elements. From both the raw materials, only linen-knitted fabric was enriched with biologically active medicinal plants extracts closed in microcapsules to ensure high bioactive performance of the selected clothing parts. Microcapsules containing herbal extracts are fixed to the inner clothing layer in order to guarantee direct and continuous contact of herbs with ill skin. The fabrics were dyed with natural herbal extracts to avoid allergic reaction and guarantee safety for dermatological patients during clothing wearing. To ensure an effective treatment of skin problems, herbal extracts, viola tricolor and green tea with proved properties suitable for dermatitis healing, were implemented to this solution. The content of active components in herbal extracts is presented in Table 5 [45].

The extract	Flavonoids expressed as quercetin; [%]	Polyphenols expressed as rosemarinic acid; [%]	Tannins expressed as pyrogallol; [%]
Green tea	1.01 ± 0.01	5.63 ± 0.38	15.14 ± 0.15
Viola tricolor	7.61 ± 0.06*	0.44 ± 0.03	0.72 ± 0.12

Table 5.

The content of polyphenolic compounds in ethanol-water extracts (1:1) from the tested raw materials.

The results of tests conducted during 5 weeks of everyday functional clothing wearing by dermatological patients confirmed efficiency of applied method of skin treatment in improving of skin condition determined by skin moisture content (Figure 18) and transepidermal water loss (Figure 19) as well as lowering of skin illness sensation, e.g., itching feeling (Figure 20).

Figure 18.

Skin moisture content tested with the corneometric method (based on [45]).

Figure 19.

Transepidermal water loss (TEWL) measured during experiment (based on [45]).

Figure 20.

Comparison of intensity of ill skin itching tested with a numeric scale in patients before and after wearing of the tested clothing (based on [45]).

The observed changes of skin parameters tested before and after the experiment of clothing wearing proved that clothing made of naturally dyed linen-knitted fabric enriched with herbal extracts locked in microcapsules can serve as a supplement in the treatment of dermatological diseases.

7.2 Flax/hemp wound dressing

The study on the effective implementation of inherent antibacterial and antioxidant properties as well as high ability to liquid sorption of bast fibers for medical target resulted in the development of flax/hemp wound dressing. The investigation is protected by patent [46]. Carefully selected flax and hemp variety characterized by high phenolic acid content as well as the use of determined fiber processing that allows us to keep the bioactive substances in the fibers on proper level leads to obtain bioactive textile suitable to wound dressing when the structure of dressing is developed accordingly.

The developed flax/hemp wound dressing was clinically tested with patients under care of surgical clinic suffering from nonhealing venous ulcers of legs and diabetic wounds. One of the examples of the efficiency of linen dressing is nonhealing venous ulcer of the right shin of the one patient. Before linen dress application, the patient was treated with using different medicines for three years with no success (antibiotics and ointment). After the application of treatment by the linen dress, the duration of healing was 4 months.

8. Conclusion

A multiperspective approach to bast fibers reveals their high potential to be used for the development and implementation of safe barrier and functional textiles. The chemical composition of the lignocellulosic fibers, including phenolic acids, results in their unique inherent bioactivity, which cannot be found in other natural or man-made fibers can give some competitive advantage of linen/hemp bioproducts. Owing to the sensitivity of phenolic acids on some wet aggressive methods of fiber extraction and processes, the design of technological chain should be well cherry-picked and focused on keeping the active fiber components on the desired level in order to produce bioactive functional textiles. Entering of other active substances on the textile surface, such as nanosilver, nanolignin, or simply herbal extracts, can strengthen the functionality of final linen/hemp goods. The linen/hemp apparels provide well-being and optimal comfort to the users, can cause improvement of skin condition, and protect against UV radiation. Bast fiber sector covering both agriculture and industry meets environmental requirements determined by the European Green Deal (EGD) strategy and contributes to the limitation of greenhouse gasses emission. Flax and hemp cultivation and their use for different purposes are in line with aims of EGD, particularly, can have influence on the improvement of the well-being and health of citizens as well as can support activity for future generations by caring for the environment and sustainability of the holistic value chain for bast fiber bioproducts.

Bast-fiber-based textile targets the improvement of human everyday life on the following levels:

• by direct covering body of wearer ensuring optimal comfort and healthy skin,

• by sustainability and lowering of environmental impact,

• by potential to improve bioeconomy,

• by possibility to use all by-products and be in line with the zero-waste strategy.

Acknowledgments

This work was realized within Project POIR.01.01.01-00-0597/21 entitled: Development of biodegradable face mask Type II from natural fibers, which is co-financed by European Regional Development Fund and The National Center for Research and Development in Poland.