Recyclability of take-back glass fiber-reinforced blends of polyphenylene oxide with high-impact polystyrene for high-performance engineering applications

Increased recycling of plastics is an essential step toward a more sustainable use of materials, where some of the most challenging fractions are engineering materials and composites. Used pump houses prepared from glass fiber (GF)-reinforced blends of polyphenylene oxide (PPO) and high-impact polystyrene (HIPS) obtained through a take-back scheme (take-back, TB) were characterized and shredded for use in the preparation of new composites by injection molding. Initial degradation was observed on the surface of the TB parts; however, the core of the material was unaffected. Mechanical reprocessing of regrind and virgin material showed a reduction of tensile strength already at 10% regrind, which was attributed to fiber length reduction during reprocessing. At the same time, Young's modulus and extension at break were largely unaffected, confirming that 25% of TB could be included without any additional loss of properties. As a worst-case scenario, tests with extensively degraded material showed that Young's modulus and tensile strength would ultimately be reduced with an increasing amount of heavily degraded material and that a balance would have to be found between loss of properties and recycled content for heavily degraded material.