Effect of draw ratio on the mechanical properties of polypropylene self-reinforced composite

Abstract Polypropylene self-reinforced composites (PP-SRCs) are advantageous in terms of recycling, impact resistance, and price; however, a deeper understanding of their mechanical properties is required to expand their commercialization. Here, an in-depth study was conducted to understand the effect of changing PP-tape as a function of the draw ratio on the mechanical properties of PP-SRC. As the draw ratio increased, PP-tape showed higher orientation and thus significantly improved the tensile strength and Young's modulus. The tensile properties of PP-SRC showed the same trend; this was successfully predicted by employing the rule of mixtures as they were dominated by the reinforcing effect of PP-tape. Meanwhile, the impact resistance of PP-SRC improved with increasing draw ratio, but the T-peel adhesion deteriorated. This occurred because the failure mode at higher draw ratios transitioned from tape fracture to delamination, resulting in enhanced energy absorption ability, and the decrease in polymer chain mobility hindered interfacial inter-diffusion.