Effect of matrix modification by natural rubber on the performance of silk-reinforced polypropylene composites

Silk fiber-reinforced polypropylene (PP) matrix composites were prepared by compression molding. Tensile strength, tensile modulus, bending strength, bending modulus, impact strength (IS), and hardness of the prepared composite (20 wt%) were found to be 54.7 MPa, 1826.2 MPa, 58.3 MPa, 3750.7 MPa, 17.6 kJ/m², and 95, respectively. To improve the biodegradable character of the composite, natural rubber (NR) was blended (10, 25, and 50 wt%) with PP using extruder, and thin films were prepared by heat press for composite fabrication. Silk fiber-reinforced blended PP plus NRbased composites (20 wt% fiber) were fabricated and characterized. It was found that the mechanical properties of the composites decreased with the increase of NR in PP but IS improved significantly. The IS improved by 48% when 25% NR was incorporated in PP for the silk-based composites. The water uptake property of the composites was investigated. Degradation of all the composites was studied using simulating weathering, thermal degradation, and soil degradation tests. The study makes it clear that mechanical properties of silk/PP composites are greater than those of silk/PP plus NR composites. But silk/PP plus NR composites are more degradable than silk/PP composites, that is, silk/PP composites retain their strength for a longer period than silk/PP plus NR composites.