Density reduction behaviors and cell morphology in extrusion of LLDPE/wood fiber composites with physical and chemical blowing agents

Abstract

ABSTRACTFoamed wood fiber/plastic composites (WPC) with a fine‐cell structure offer many benefits compared with the unfoamed WPC, such as the reduced material cost and density, the improved toughness, and the enhanced processability. However, it is extremely challenging to achieve the desired density reduction and obtain a fine‐cell structure simultaneously. One of the obstacles is that the volatiles released from the wood fiber (WF) during processing should be suppressed to ensure a fine‐cell structure. Linear low‐density polyethylene (LLDPE) has a relatively low melting temperature, and it can reduce the processing temperature and suppress volatiles when used as a polymer matrix for foamed WPC. This paper systematically investigates the foamability of LLDPE/WF composites in a continuous foam extrusion, with both a chemical blowing agent and a physical blowing agent (PBA). It turns out that the PBA‐based foaming led to a smaller cell size and a narrower cell size distribution. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48829.