Cost effective reprocessing of polyurethane by hot compression moulding

Impending legislation and increasing landfill tax will mean that a far greater proportion of thermosetting polymers will have to be recycled. This paper investigates a method for the mechanical recycling of thermoset polyurethane. Reaction injection moulded (RIM) polyurethane (PU) was granulated and introduced as filler in novel moulding compounds. The polyurethane recyclate granules were compounded with polyester resin for compression moulding. A variety of different materials were moulded to demonstrate the recycling possibilities, these included non-reinforced filled thermoset, glass fibre reinforced compounds and sandwich materials with a core containing recyclate. Mechanical testing of the materials showed that the addition of polyurethane recyclate increased flexibility and toughness of the mouldings, when compared with compounds containing mineral fillers. The increased toughness is explained by the microstructure, the PU granules rubber toughen the resin by allowing micro-cracking of the thermoset resin matrix without brittle failure. Recycled polyurethane particles can be used as functional filler in thermoset-moulding compounds to improve the impact toughness of normally brittle materials.