A Systematic Literature Review of Waste Polypropylene Reinforced with Glass Fiber: Mechanical and Thermal Properties in the Context of Sustainability

Recycled polypropylene reinforced with glass fiber (rPP-GF) represents a promising sustainable material alternative addressing global imperatives for environmentally responsible manufacturing. This systematic literature review examines the mechanical, thermal, and sustainability performance of rPP-GF composites based on 66 peer-reviewed studies published between 2014 and 2024, following PRISMA guidelines. The evidence demonstrates that glass fiber reinforcement significantly enhances mechanical and thermal performance. Compared to virgin counterparts, rPP-GF composites reduce environmental impact. However, technical challenges, including fiber attrition during reprocessing and a lack of standardized testing protocols, remain significant barriers. Future research should prioritize unified testing frameworks, hybrid filler systems, and advanced recycling technologies for enhanced circular economy applications.