Comparative study of high-density polyethylene-based biocomposites reinforced with various agricultural residue fibers

The characteristics of natural fibers have significant effects on properties of natural fiber/polymer composites (NFPCs). Herein, agricultural residues (ARs) fibers, including wheat straw (WS), rice straw (RS), rice husk (RH), sugarcane bagasse (SB), cotton stalk (CS), and Moso bamboo fiber (MB) were selected as reinforcement to fabricate NFPCs via extrusion processing. The chemical and physical properties of the fibers were determined. The mechanical properties, hygroscopicity, rheological properties, and dimensional stability of the resulting composites were studied. The MB fiber had the highest α-cellulose content (46.4 %), lignin content (26.4 %), and crystallinity index (60.2 %). The CS fiber contained the lowest α-cellulose content (29.1 %) and the highest extractive content (8.9 %). RS and RH fibers, which with much higher ash content than the other fibers, had the lowest lignin (11.9 %) and extractive (2.7 %) contents, respectively. A reduction of fiber length and L/D can be observed after extrusion. SB fibers (794.4 μm) was longer than other ARs fibers, and the MB and RH had the highest (3.6) and lowest (2.0) L/D, respectively. Addition of ARs fibers in HDPE can improve the tensile and flexural strength, and the mechanical modulus of composites was more than 3 times higher than HDPE. The best mechanical properties, dimensional stability, and thermostability were obtained for the MB-based composite. Composite filled with RH showed the poorest mechanical properties but the best processability. CS-and RS-based composites exhibited much lower Vicat softening temperature (85.57 °C and 87.24 °C) due to the lower α-cellulose content and higher extractive content in the fibers. The ARs had the great potential as fillers to prepare NFPCs. It is anticipated that the findings will provide useful design inputs for making construction and building materials.