Agro-residue reinforced high-density polyethylene composites: Fiber characterization and analysis of composite properties

The main objective of this research was to study the potential of agro-residues such as wheat straw, cornstalk and corncob as reinforcements for thermoplastics as an alternative to wood fibers. High-density polyethylene (HDPE) composites were prepared with a high content of agro-residues (65 wt.%). Surface chemistry of agro-residues was studied in comparison with wood flour with a view to evaluate its importance in determining the end-use properties of the composites. Surface chemistry showed a more carbon rich surface for wheat straw compared to cornstalk, corncob and wood flour. Thermal degradation characteristics of the fibers were studied to investigate the feasibility of these fibers to the processing point of view. The results showed that the agro-residues starts decomposition as low as 200 °C indicating that they can be processed with thermoplastics having a melt temperature less than 200 °C. Mechanical properties and water absorption properties of the composites were studied to evaluate the viability of these fibers as reinforcements in HDPE. Wheat straw filled HDPE composites exhibited superior mechanical properties compared to cornstalk, corncob and even wood flour filled HDPE, where as cornstalk showed comparable mechanical properties to that of wood flour–HDPE composite. All the composites exhibited a high uptake of water due to the high amount of filler present and incorporation of compatibilizer decreased the water uptake of the composites. It was observed that irrespective of the presence of compatibilizers, flexural properties of the composites were decreased considerably after water absorption.