Cellulose crystallinity can be altered by various treatment methods, including mechanical or chemical treatments, which can affect the properties of thermoplastic composites. In this study, the crystallinity of cellulose was manipulated using mechanical ball milling. The primary objective was to assess the impact of altering the cellulose crystallinity on the overall performance of high-density polyethylene (HDPE)-based composites. The mechanical and structural properties of the composites were assessed using tensile and impact tests, attenuated total reflectance infrared ( ATR-IR ) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The degradation properties of the HDPE composites were evaluated using a soil-burial degradation test. The impact of cellulose crystallinity on the mechanical properties of HDPE composites showed a marginal enhancement of 5% in tensile strength with the incorporation of 2% low-crystallinity cellulose (LCC). The highest impact strength of the HDPE composites was attained by the incorporation of 6% LCC. ATR-IR analysis showed that the peak intensity of the HDPE-LCC composite decreased, whereas the HDPE composite with high-crystallinity cellulose (HCC) did not exhibit changes in peak intensity compared to the HDPE spectrum. SEM examination showed that LCC possessed superior dispersion in the HDPE matrix compared to that of HCC. Thermal degradation decreased by up to 32% with the addition of HCC and LCC. A soil burial degradation study showed that the mechanical properties of the HDPE-LCC composite deteriorated more than those of the HDPE-HCC composite after 24 months. This study concluded that altering the crystallinity of cellulose can lead to composites with tailored properties.

This work studied biocomposites based on a blend of low-density polyethylene (LDPE) and the ethylene-vinyl acetate copolymer (EVA), filled with 30 wt.% of cellulosic components (microcrystalline cellulose or wood flour). The LDPE/EVA ratio varied from 0 to 100%. It was shown that the addition of EVA to LDPE increased the elasticity of biocomposites. The elongation at break for filled biocomposites increased from 9% to 317% for microcrystalline cellulose and from 9% to 120% for wood flour (with an increase in the EVA content in the matrix from 0 to 50%). The biodegradability of biocomposites was assessed both in laboratory conditions and in open landfill conditions. The EVA content in the matrix also affects the rate of the biodegradation of biocomposites, with an increase in the proportion of the copolymer in the polymer matrix corresponding to increased rates of biodegradation. Biodegradation was confirmed gravimetrically by weight loss, an X-ray diffraction analysis, and the change in color of the samples after exposition in soil media. The prepared biocomposites have a high potential for implementation due to the optimal combination of consumer properties.