Recycling concepts for thermoplastic composites (Reprinted from Enercomp 95 - Proceedings of the International Conference on Composite Materials and Energy, May 8-10, 1995)

Thermoplastic short fibre composite materials are increasingly being used as insulating materials in electricity distribution. Economically they possess good opportunities for material recycling and reuse due to the high virgin price. To investigate the recycling potential of post-consumer components, PPS40%GF and PBT30%GF, representing commonly used insulating materials, have been artificially aged and recycled. To simulate 10 years of service life, injection moulded tensile bars have been aged in different environments varying temperature, humidity and pH. After accelerated ageing, the ageing state has been characterized by tensile and impact strength, viscoelastic behaviour (DIMTA), molecular weight, crystallinity (DSC) and fracture behaviour (SEM). These properties have been compared to virgin material. The aged materials have been recycled by regranulation and compounding with different ratios virgin/aged material and different coupling agents to repair the glass-matrix interface. Injection moulded compounds were characterised by short and long term properties. Recompounding PBT30%GF with virgin material and no added coupling agents results in a partial recovery of the fibre-matrix adhesion. Based on the first short-term characterisations PBT30%GF seems not very suitable for reuse in primary applications. PPS40%GF seems more suitable for reuse in primary applications after recycling. Although the short-term mechanical properties of the aged batches do not recover after recycling, the fibre-matrix adhesion improves especially when adding coupling agents. Further long-term testing in creep and humid environments during the remaining part of this project will show whether the improved interface properties make recycled materials valuable for reuse in various industrial applications.