Repairing Broken Thermoset Pieces Using Diffusional Pretreatment and Cure with Uncured Resin

Repairing broken thermoset pieces is often carried out, although optimization of the technique may not have been achieved. A new way is investigated using a thermoset based on an unsaturated polyester resin allowing the final product to exhibit good mechanical properties. The procedure described here consists of two stages: putting some pure resin on the surface of the broken thermoset piece over a given a period of time, then putting this pre-treated piece in the mould with fresh uncured thermoset (made of pure resin with fibreglass and filler) necessary to fill the mould, and curing this system. The pre-treatment with the pure resin is made on the surface of the broken thermoset piece which will be in contact with the fresh uncured thermoset. The mechanical properties in elongation and flexion of the final material are measured. It appears that not only the diffusion of pure resin into the broken thermoset is responsible for an increase in these mechanical properties, but also that the time of diffusion is of interest, 24 h being better then 4 h. With a time of diffusion of 24 h, the mechanical properties are nearly similar to those obtained with the original non broken thermoset piece.