Influence of carboxy-terminated hyperbranched polyester and polyethylene glycol on the mechanical and thermal properties of polylactic acid/straw flour composites

Polylactic acid (PLA) wood-plastic composites have a significant advantage over traditional petroleum-based plastics due to their biodegradability. However, PLA has several shortcomings, including high brittleness, low heat resistance, slow crystallization, and poor compatibility with biomass materials, which have limited its potential applications. In this paper, we investigated the effects of carboxy-terminated hyperbranched polyester (CHBP) on the mechanical, crystalline, and thermal properties of PLA/straw flour (SF) blends through extrusion injection molding. Additionally, we added the traditional plasticizer polyethylene glycol (PEG) to synergize with CHBP to enhance the toughness of PLA/SF composites. Our results showed that the appropriate addition of CHBP effectively improved the interfacial bonding between PLA and straw flour. The incorporation of CHBP also improved the tensile strength, bending strength, impact strength, elongation at break, thermal stability, and crystallization rate of the composites. Furthermore, the addition of both CHBP and PEG significantly improved the impact strength of the composites compared to using PEG alone. This method also improved the heat resistance of the material and reduced the migration of plasticizers. Our study demonstrates the feasibility of using hyperbranched polymers and plasticizers to enhance the toughness, thermal stability, and crystalline properties of PLA wood-plastic composites, providing a new approach to improving the properties of these composites.

Combined influences of trioctyl phosphate and modified microcrystalline cellulose from oil palm empty fruit bunch waste on characteristics of polylactide composite

Polylactide (PLA) is renewable and biodegradable with good strength and modulus, but its poor toughness and flammability limit its use in the automotive and electronics fields. In this study, the toughness and flame retardancy of PLA were enhanced with multifunctional additives. PLA was compounded with trioctyl phosphate (TOP) and reinforced with a filler of maleic anhydride-modified microcrystalline cellulose (MAMC) derived from oil palm empty fruit bunch. TOP was an effective impact modifier for PLA and retarded total flame time. Compared to neat PLA, the impact strength of PLA with 10 phr of TOP increased by almost 260 %. The incorporation of TOP and MAMC further improved the properties of the PLA composite, which showed excellent flame retardant behavior. In UL94 conditions, the best-performing sample achieved the highest rating of V-0, self-extinguishing in 1.6 ± 0.5 s and producing no melt dripping. MAMC also significantly increased the thermal stability of the PLA-based composite. The best-performing formulation (PO10MAMC15) showed the potential to be used in the automotive and electronic industries.