Processing, mechanical and thermal behavior assessments of polycaprolactone/agricultural wastes biocomposites

Abstract

In this paper, brewer’s spent grain (BSG) was applied as potential lignocellulose biofiller in biocomposites based on polycaprolactone (PCL). The PCL/BSG biocomposites filled with varying content of biofillers were prepared via low-temperature melt-compounding. These conditions allow limiting thermal degradation of used biofillers during processing. The influence of biofiller content (ranging from 25 to 200 parts by weight on 100 parts of PCL) on processing, static and dynamic mechanical properties, thermal properties and water absorption was investigated. For better characterization of interfacial interactions between PCL and BSG obtained results were compared with properties of biocomposites filled with other agricultural waste - wheat bran (WB). It was observed that higher amount of amino-acids present in the BSG (21wt.%), in comparison to WB (4wt.%), caused partial plasticization of PCL matrix, which improved processing but simultaneously deteriorated the mechanical properties of PCL/agricultural wastes biocomposites. The melt flow index of PCL/BSG was two-folds higher than for PCL/WB composites. The best mechanical properties were achieved in case of PCL/WB biocomposites, which showed higher values of storage modulus, 5% higher values of hardness and at least 30% higher tensile strength in most cases. Obtained results suggest better compatibility between the PCL matrix and WB in comparison to the BSG, which were explained by differences in the content of proteins in applied biofillers. The conducted investigations showed that BSG and WB could be successfully applied as a low-cost substitute of lignocellulose fillers in polymer wood composites and biocomposites.