Biodegradability assessment of HDPE-based biocomposites: Influence of starch and fiber composition

Abstract

This research aims to analyze the biodegradation dynamics of a tertiary composite blend, including High-Density Polyethylene (HDPE), starch and linen fiber, and their combined effect on decay processes in authentic environmental settings. It investigates the relationship between fiber content and decomposition rates, details the biodegradation mechanisms, and evaluates the reactive profiles of the involved constituents. Decay kinetics and the biodegradation mechanism of three formulations: HDPE60S40, HDPE60S20F20, and HDPE60S30F10, representing composites with 60 % HDPE, complemented by 40 %, 20 % starch and 20 %, 10 % linen fiber, respectively, are examined. HDPE60S30F10 is noted for its superior biodegradation rates, showing a 1.2 % weight loss in soil and 9.89 % in marine conditions and an increased resistance to shearing forces, whereas HDPE60S40 recorded a weight loss of 0,63 % in soil and 2.59 % in seawater against 1,7 % and 6.64 % in soil and seawtaer, respectively recorded with HDPE60S20F20. Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations complement these findings, presenting HDPE60S40 as the most rigid, HDPE60S20F20 as the most ductile with a bulk modulus of 13.34 GPa, and HDPE60S30F10 exhibiting the best shear resistance with a shear modulus of 12.48 GPa. Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR) analyses confirm microbial involvement and significant surface erosion, particularly indicating particularly starch degradation. The results suggest that integrating linen fiber into the composites enhances biodegradation.