Wood-plastic composites from bio-based polymers and wood fibers (bio-WPC) provide an improved sustainability and carbon footprint compared to conventional composites. Actually, the implementation of this approach into industrial applications is hindered by the missing knowledge on the mechanical and thermo-mechanical properties of such bio-WPC. In this study, the properties of a bio-WPC from bio-based polyamide 11 (PA 11) and chemically modified beech fibers were investigated. The chemical modification of the beech fibers by an alkaline treatment with an aqueous solution of sodium hydroxide (NaOH) was done to support the melt processing and adhesion to the PA 11 matrix. Analysis of the modified fibers by Thermogravimetric Analysis (TGA) proved an increased thermal stability, as identified by an increase of the extrapolated TGA onset temperature from 290 to 330 °C. This improvement resulted from hemicellulose removal, as confirmed through Attenuated Total Reflection Inf rared Spectroscopy (ATR-FTIR). Consequently, mechanical and thermo-mechanical analysis of the processed bio-WPC showed an increase in elastic modulus and storage modulus of the composites by the chemical treatment of the fibers. This effect was attributed to an increased number of hydrogen bonds between the modified beech fibers and the PA 11 matrix. The overall mechanical properties of the investigated bio-WPCs support their use as sustainable construction material for technical applications

The goal of this study was to investigate the synthesis and the resulting thermal, rheological, and mechanical properties of polyamide 6/11 copolymers (PA 6/11) as a function of their composition and to further investigate their usability as matrix polymers for wood-plastic composites (WPC). A significant composition dependency of the melting temperature was found due to the hindered crystallization of the PA 6/11 copolymers with increasing content of the minor component. In result, the lowest melting temperature of the copolymers was measured at 120 8 C for 40 wt % of E-caprolactam (PA 6/11-40/60) by DSC analysis. Due to its low melting point and feasible mechanical properties, a copolyamide with 70 wt % of E -caprolactam (PA 6/11-70/30) was chosen as matrix material for the processing of WPC. Incorporation of 30 wt % of wood fibers into PA 6/11-70/30 caused a significant increase in tensile modulus and a decrease in tensile strength and strain at break. However, the processed WPC still showed an exceptional ductility with a strain at break of 15 to 20%

In this study, the reinforcement of bio-based Polyamide 11 (PA 11) with physico-chemically modified Beech Fibers was investigated. In a first step, an improvement of the thermal stability of the fibers was achieved by a two-step alkaline treatment with sodium hydroxide and hydrogen peroxide. This effect was attributed to the removal of the hemicellulose from the fiber surface, as verified by Attenuated Total Reflection Infrared Spectroscopy (ATR-FTIR). Consequently, the onset-temperature of thermal degradation as measured by Thermo-Gravimetric Analysis (TGA) increased from 285 °C to 337 °C. Given this, the compounding of the modified fibers with the low melting bio-based Polyamide 11 was done in a lab-scale co-kneader and followed by subsequent injection molding of test specimens. Analysis of the mechanical and thermo-mechanical properties of the processed Wood Plastic Composites showed a beneficial effect of the chemical fiber treatment on composite stiffness, and allowed for suggestions to improve the up scaling of the processing.

Summary The resulting mechanical and thermo‐mechanical properties of discontinuously and continuously processed biogenic wood‐plastic composites (bio‐WPC) from polyamide 11 and chemically modified beech particles are investigated. It is found that continuous processing with a twin‐screw extruder (TSE) and subsequent industrial scale injection molding leads to a lower elastic modulus, an equal tensile strength, a higher strain at break and a lower glass transition temperature as compared to discontinuous processing with an internal mixer (IM) and subsequent laboratory scale injection molding. This is attributed to a more distinctive beech particle size reduction and shear stress induced chain scission during TSE processing and subsequent injection molding.