Investigation on the influence of multi-step processing on the mechanical and thermal properties of cellulose reinforced EVOH composites

Abstract

The industrial fabrication of thermoplastic composites involves the consecutive application of different melt processing techniques such as extrusion and compression moulding. In the course of processing, the material properties can undergo significant changes that determine the final properties of the product. Thermoplastic composites created by implementing cellulose - a relatively low cost, bio-renewable and bio-degradable polymer with high mechanical properties and low density - as a filler show promising results. In order to establish a cost-efficient, scalable and sustainable production in industry it is important to understand how melt processing affects the mechanical and thermal properties of cellulose thermoplastic composites. Microcrystalline cellulose (MCC) and cellulose nanocrystals (CNC) were combined, in turn, with ethylene vinyl alcohol (EVOH) using a high shear screw configuration for extrusion to create composites with improved dispersion. Melt processing steps included compounding in the extruder followed by compression moulding. No thermal degradation was found in the course of processing. Results revealed an elevated crystallization temperature for composites due to a nucleating effect of cellulose. When the compression moulding step was repeated, a processing-induced orientation led to an increase in crystallinity which is higher in pristine material as strong filler-matrix interaction inhibits molecular movement in composites.