Effect of hydroxyl‐terminated hyperbranched polyesters with various molecular weight on mechanical properties, thermal stability, and water absorption properties of polylactic acid wood‐plastic composites

Abstract In the field of environmentally friendly materials, improving the interfacial bonding between biomass fillers and polylactic acid (PLA) has been a popular area of study. This study examined the effects of four distinct molecular weight end‐hydroxy hyperbranched polyesters (HHBP) on the extrusion and injection molding processes used to create PLA/straw powder composites. According to tests of mechanical properties, the composites' tensile strength, elongation at break, and impact strength increased by up to 15.2%, 12.18%, and 41.94%, respectively. Thermogravimetric tests revealed that the composites' initial thermal decomposition temperature was raised by as much as 5°C. The differential scanning calorimetry results showed an increase in crystallinity of up to 6.27%. The composites' water absorption was enhanced by the addition of HHBP, but the water molecules' diffusion rate was slowed down. By adjusting the molecular weight of HHBP, this study shows that the corresponding properties of the composites can be improved. Highlights HHBP strengthened the PLA‐biomass filler interfacial bond. HHBP enhanced composites' toughness, thermal characteristics, and crystallinity. HHBP achieved a lower diffusion rate of water molecules in the composites.