Incorporation of natural fibres in a biodegradable thermoplastic polymer via a twin-screw extruder

Abstract

Incorporation of a widely available agricultural by-product, wheat bran, into polylactic acid (PLA) have been investigated and compared to miscanthus and highly cellulosic fibres. They were compounded at different ratio from 10 to 40% wt. Influence on energy consumption during the process showed that the more filler added, the more energy needed but wheat-bran based composites consume less energy to be processed than the other fibres (131 W.h/kg for SME instead of 144 W.h/kg for miscanthus fibres in the case of the 40% wt fibre-filled PLA compounds). Viscosity behaviour was evaluated, highlighting a thinning effect of the wheat bran when compounded to PLA. Comparison of mechanical properties raised some negative effects on composite strength (-59% for tensile strength for the PLA-40% wheat bran compound) and stiffening was not as important as comparative fibres (4290 MPa for tensile modulus instead of 8790 MPa for miscanthus fibres in the case of the 40% wt fibre-filled PLA compounds). Complex chemical composition of the bran with lower fibre content can explain this. However, wheat bran is a promising filler to produce cheap sustainable composites.