Influence of the blending method over the thermal and mechanical properties of biodegradable polylactic acid/polyhydroxybutyrate blends and their wood biocomposites

This study focused on the effect of the processing method on the thermal, mechanical, and biodegradation properties of polylactic acid/polyhydroxybutyrate (PLA/PHB) blends and their wood biocomposites. The blending techniques were dry-blending or twin-screw extrusion, both followed by compression molding. PLA/PHB blends were prepared using 15 and 25% wt. of PHB and biocomposites with 20 and 30% wt. of wood particles. Moreover, a compatibilizer was used during the extrusion process to achieve better matrix-fiber adhesion. The results showed that the crystallinity of PLA significantly increased with PHB and wood, especially after twin-screw extrusion. The best results in tensile, flexural, and impact strength were obtained with the extruded and compatibilized PLA/PHB blends, with values higher than the neat biopolymers. The compatibilized biocomposite with 15% wt. PHB, and 20% wt. wood particles showed higher tensile, flexural, and impact properties than PLA. The biodegradation test showed that all samples were disintegrated (above 40%) after 40 days in compost medium, observing slight decreases in the biodegradation rate when PHB or wood particles were added. Even when the lower mechanical properties were obtained with the dry-blending technique, they are still competitive for different applications, providing the possibility to produce blends and biocomposites, avoiding the extrusion process that requires more energy consumption and longer processing times.