Ahmed Koubaa
Professor, Université du Québec en Abitibi-Témiscamingue Research Interest: wood quality, bioproducts, bioenergy, biocomposites Wood biotheramal treatment
Professor, Université du Québec en Abitibi-Témiscamingue Research Interest: wood quality, bioproducts, bioenergy, biocomposites Wood biotheramal treatment
This study investigates alternatives that can improve the internal bond strength (IBS) of paper by pulp refining and paper press-drying (PD). The improvement mechanisms of IBS and their impact on the strength development of high-yield pulps are discussed. All experiments were conducted using a factorial design where the factors were four pulp types (one spruce thermomechanical (TMP) and three chemi-thermomechanical (CTMP) from spruce, birch, and aspen), three refining levels, three PD temperatures and three pressures. The effects of these treatments on the physical and mechanical properties of paper were studied using an analysis of variance. Refining changed the fibre surface, thereby promoting mechanical adhesion. PD temperature softened the fibres and changed their surface chemistry, while PD pressure improved the contact area between fibres. These changes led to an important improvement in IBS which explained, to a large extent, the variations in paper properties. Compared to air-dried paper, PD paper showed much higher properties for most tested pulps at all refining levels. These results were due to the increase in bonded areas. PD at 175°C substantially improved the wet tensile strength of paper due to the flow of lignin on the fibre surface, which protects the hydrogen bonds from moisture.
Part of the book: Pulp and Paper Processing
We investigated the effects of polymer blend variation on the physical, mechanical, and thermal properties of wood-polymer composites (WPC). We used high-density polyethylene (HDPE) and polypropylene (PP) and a combination of 80% PP, 20% HDPE, and 80% HDPE, 20% PP as polymer blends for WPC formulations to simulate recycled plastics. We used black spruce (Picea mariana Mill.) hammer milled fibers (75–250 μm) at 35 wt% as a filler for all the formulations. A two-step process was used for WPC manufacturing; pellet extrusion followed by test samples injection. Tensile and three bending tests characterized the WPC mechanical properties. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) characterized the WPCs’ thermal properties. Water absorption and contact angle measurements assessed the composite dimensional stability. Infrared spectroscopy (FTIR) and electron scanning microscopy (SEM) investigated the WPCs’ surface chemistry and microstructure. Mechanical properties and dimensional stability varied according to polymer composition, with better performance for WPC containing higher PP proportions. Thermal properties varied with the polymer composition in the WPC, with better thermal stability for the formulation containing higher HDPE proportions. Surface chemistry analysis did not reveal any chemical changes on the WPCs surface. Scanning electron microscopy analysis revealed distinct phases in all WPCs without evidence of interfacial adhesion.
Part of the book: Biocomposites