Eco-friendly sisal, basalt, and recycled nylon fibers-reinforced polypropylene composites: A step towards sustainable developments

Recycling the end products molded from polymeric composites is gaining colossal attention worldwide from researchers and engineers. Still, it faces enormous performance challenges due to the flux of composite products available in the current automotive market. The present work is a step towards exploring the possibilities of employing sisal fiber (SSL), basalt fiber (BF), and recycled nylon (RNF) fiber-reinforced polypropylene composites and their impact on mechanical properties. This investigation explores the impact of change in aspect ratio of the fibers during recycling in deciding the composites' mechanical properties. The highest loss in tensile properties was reported for the BF-reinforced polypropylene composites. Pristine SSL-, BF-, and RNF-reinforced composites reported tensile strengths of 37.09, 47.93 , and 39.40 MPa, respectively , while their recycled counterparts showed reduced values of 33.78, 34.93, and 38.01 MPa. Likewise, flexural strength of 42.19, 78.56, and 50.36 MPa was recorded for the recycled SSL, BF, and RNF-reinforced PP composites compared to a flexural strength of 44.26, 99.01, and 53.69 MPa for their fresh counterparts, expressing a negligible decrease for SSL and RNF-reinforced but an apparent decrease for basalt-reinforced composites over non-recycled ones. Interestingly, the impact strength of all the composites marginally increased or was unaffected due to the decreased aspect ratio and degradation of the broken fibers. FE-SEM images confirm that SSL and BF lost ∼67 and 89.88 % in the aspect ratio, while there were minimal changes in the aspect ratio of RNF. Based on these results, the potential for composite recycling follows the following order: RNF > SSL > BF. The meticulous use of mechanical recycling of the short fiber reinforced polymeric composites may save energy and resources, paving the path towards sustainable materials development.