Processing and characterization of wood plastic composites from bio-based polyamide 11 and chemically modified beech fibers

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.