Sustainable green composites from biodegradable plastics blend and natural fibre with balanced performance: Synergy of nano-structured blend and reactive extrusion

We herein report a unique scientific strategy in engineering green composites with excellent balanced performance of stiffness, toughness and heat deflection temperature (HDT). To achieve such target, a high melt strength bioplastic blend of poly (butylene succinate), PBS and poly (butylene-adipate-co-terephthalate), PBAT with super toughness could take-up stiff natural fibres like inexpensive purpose grown Miscanthus fibre and Oat hull (a co-product from food industry) in the green composite structure through reactive extrusion. The novelty of this work is to allow the free radical reaction to occur within polymer matrix and between the blend and natural fibres by introducing biomass from a side feeder, aiming to achieve matrix toughening and polymer/fibre interface enhancement simultaneously. Tensile modulus of the bio-blends was improved by maximum 650% with the reinforcement of 40 wt% agricultural by-products. For equal amounts of 40% biomass fibres, the Miscanthus fibre is more suitable to strengthen the biopolymers, in terms of higher modulus (3.0 GPa), higher HDT (110 degrees C) and lower water absorption (3.4%); however, the oat hull composites show much higher impact strength of 83 J/m. A systematical structure-properties relationship study indicates that higher aspect ratio, higher cellulose contents and stronger interfacial actions account for the higher stiffness and HDT of the Miscanthus fibre composites compared to the oat hull-filled counterparts. This abundant biomass has potential to fabricate sustainable composites to substitute certain fossil fuel-based plastics in terms of mechanical and thermal properties, as well as cost and energy-saving via using the industrial friendly technology as proposed here.