Tensile and Impact Properties of Mechanically Recycled Polypropylene: A Structured Literature Review

Abstract

This literature review aimed to analyze the mechanical and thermal behavior of recycled polypropylene (PP), with a specific focus on tensile and impact performance. A structured search was conducted using Google Scholar, selecting eight scientific articles published between 2017 and 2025 that met inclusion criteria such as full-text availability, focus on mechanical recycling, and reporting of key mechanical properties. The selected studies were analyzed and compared based on material composition, additive use, and number of recycling cycles. The results showed that tensile strength was generally retained, with minimal reduction in some cases, especially when fillers such as talc were used. However, impact resistance decreased significantly with increasing recycled content, particularly in the absence of elastomeric modifiers. Differences in feedstock origin, test protocols, and additive strategies were identified as key sources of variability. Despite these challenges, promising approaches were found, including the use of tailored additive systems, closed-loop recycling strategies, and advances in preprocessing technologies. It is concluded that recycled PP can be a technically viable material for various applications, particularly when combined with targeted additives and supported by standardized characterization methods.