Hybrid green composites using rice straw and jute fabric as reinforcement for soy protein-based resin

Abstract

In this research, high amounts of the world's most wasted agricultural residue (rice straws) were utilized to produce hybrid green composites. Rice straws (RS) were needle-punched into jute fabric to form hybrid reinforcement mats which were impregnated with a soy protein isolate resin (SPR). Thermoset hybrid composites were produced at three different fiber contents of 40, 50, and 60% by wt. They were characterized for their tensile, flexural, interfacial, fractural, and hygroscopic properties. The hybrid composites with 40% fiber content enhanced Young's modulus (Ey) and ultimate tensile strength (TS) of the pure resin by 200% and 47%, respectively, compared to pure resin. With increasing fiber content, mechanical properties such as Ey, TS, flexural modulus, and flexural strength decreased, indicating insufficient resin volume. Interfacial shear strength values of RS/SPR and Jute/SPR were measured at 2.68 and 4.25 MPa, respectively. The high volumes of low-density RS and higher viscosity of the resin used in the hybrid composites seemed to overwhelm the resin's capacity to effectively wet the fibers. Insufficient wetting and low interfacial shear strength (IFSS) resulted in fiber pull-outs at fracture surfaces. Furthermore, as fiber content increased from 40 to 50 to 60%, moisture absorption increased from 10.4 to 12.9 to 22.6%, respectively. This is in spite of the fact that SPR was the most hydrophilic component of the three constituents. These results suggest that the high volumes of low-density fibers induce structural defects and exhaust the resin's wettability. Overall, the hybrid biodegradable composites had good tensile properties for use in packaging, transportation, housing, and furniture.