Biomass pinecone powder inclusion for mitigating mechanical degradation in recycled polypropylene extrusions

Abstract

Recycling of polypropylene (rPP) poses challenges due to the degradation of its mechanical properties during multiple heating and cooling processes, which limits its practical applications. To address this issue, this study explores the incorporation of pinecone powder (PCP) as a sustainable reinforcing filler to improve the thermomechanical properties of rPP. The motivation stems from the need for eco-friendly materials that can reduce the effects of thermal degradation while enhancing mechanical performance. Experimental results showed that rPP composites containing 15 wt% PCP achieved significant improvements, with tensile strength increasing by 22 % (from 21.17 MPa to 25.86 MPa) and flexural strength by 24 % (from 35.2 MPa to 43.75 MPa) compared to neat rPP. Fourier-transform infrared spectroscopy (FTIR) confirmed strong interfacial bonding between the rPP matrix and PCP, contributing to improved tensile and flexural properties. Thermogravimetric analysis (TGA) revealed enhanced thermal stability, delaying the onset of thermal degradation. Scanning electron microscopy (SEM) showed that PCP expansion at high temperatures led to better distribution of particles, though non-uniform particle sizes and interfacial debonding were observed at elevated temperatures. These findings highlight PCP’s potential as a bio-based filler for improving rPP properties, although further optimization of particle size distribution and interfacial adhesion is necessary for industrial applications. The results demonstrate the potential of PCP to address both mechanical and environmental challenges in polypropylene recycling.