Recycling waste polyurethane from the refrigeration industry as filler in SBR/NR composites for industrial applications

The refrigeration industry produces millions of tons of waste polyurethane (PU) every year, which can cause environmental damage and human health problems. This article analyzes the use of waste PU as filler in composites made of styrene butadiene rubber (SBR) and natural rubber (NR) to produce shoe soles. The interfacial interaction of said filler was evaluated by the Flory-Rehner method (swelling) using the equation developed by Lorenz-Park. The results of this evaluation were later compared with those obtained by the Mooney-Rivlin method using the data from stress-strain tests. According to the results of the tensile strength tests, the composites filled with waste PU present stress-strain curves that are like those of metallic materials that have low elastic strength but high plastic strength. Using the Lorenz-Park equation, the filled composites examined in this study exhibited values above 0.7, which means a strong filler-rubber interaction. Scanning Electron Microscopy and Fourier-Transform Infrared Spectroscopy were used to investigate the morphology of the composites in detail.