Highly sustainable composites were produced by melt compounding polylactide (PLA) with almond shell flour (ASF), a processed byproduct of the food industry, at a weight content of 30 wt.-%. However, due to the lack of miscibility between PLA and ASF, both being raw materials obtained from crops, resultant green composite presented poor ductility and low thermal stability. To overcome this limitation, maleinized linseed oil (MLO), a multi-functionalized plant-derived additive, was originally incorporated as a reactive compatibilizer during the extrusion process. Both chemical and physical characterizations showed that 1-5 parts per hundred resin (phr) of MLO successfully serve to function as a novel compatibilizer on the PLA/ASF composites, leading to highly sustainable materials with balanced mechanical, thermal, and thermomechanical properties. Achieved compatibilization was particularly related to a dual effect of plasticization in combination with grafting. The latter effect was ascribed to the formation of new carboxylic ester bonds through the reaction of the multiple maleic anhydride groups present in MLO with the hydroxyl terminal groups of both PLA chains and lignocellulose on the ASF surface. The fully bio-based and 2 biodegradable composites described herein give an efficient sustainable solution to upgrade agrofood wastes as well as contributing to reducing the cost of PLA-based materials.

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This work reports the enhancement of the properties of poly(butylene succinate) (PBS) composites containing 30 wt% almond shell flour (ASF) by using different compatibilizer families: epoxy, maleic anhydride and acrylic. With regard to the epoxy compatibilizers, epoxidized linseed oil (ELO) and epoxidized soybean oil (ESBO) were used. Two maleic anhydride-derived compatibilizers, namely, maleinized linseed oil (MLO) and dodecenyl succinic anhydride (DDSA) were used. Finally, two acrylic monomers, namely methyl methacrylate (MMA) and acrylic acid (AA) were employed. Uncompatibilized and compatibilized PBS/ASF composites were characterized in terms of their mechanical properties, morphology, thermal behaviour and thermomechanical performance. The obtained results suggest that all three vegetable oil-derived compatibilizers (ELO, ESBO and MLO) give a remarkable increase in ductile properties while poor compatibilization is obtained with the acrylic monomers. These vegetable-oil derived compatibilizers could represents an interesting environmentally friendly solution to compatibilizing polyester-type polymers and their composites with lignocellulosic materials.

Effect of different compatibilizers on injection-molded green composite pieces based on polylactide filled with almond shell flour. Composites Part B Engineering.

Enhancement of the mechanical and thermal properties of injection-molded polylactide parts by the addition of acrylated epoxidized soybean oil.