A Useful Tool to Recycle Mixed Plastics Blends

Abstract

In the pursuit of more sustainable practices within the circular economy, the estimation of polymer contents in mixed plastic blends is essential. This study presents a simple method for determining the polypropylene (PP) and polyethylene (PE) content in heterogeneous mixtures of recycled plastic. A calibration curve was developed using differential scanning calorimetry data, allowing for rough estimations of PP and PE ratios. Seven recycled PE/PP blends were analyzed, and cross-contamination of polymers was observed. Linear and quadratic fits of the enthalpy of fusion and degree of crystallinity were applied to estimate polymer contents. The quadratic fit of the degree of crystallinity provided the most accurate estimation, with standard deviations of 1.4% for PE and 3.7% for PP. This method offers a simple and accessible tool for small-scale recyclers to improve the efficiency of plastic recycling, filling a gap left by more complex scientific studies on polyolefins.