Polymerisation of glycidyl methacrylate resin modified with unsaturated polyester from recycled PET

Environmental concerns regarding the increase in solid waste and its impact on greenhouse gas emissions have been growing in the recent years. The improvement of recycling and the production of biosourced materials are well-known solutions in the research industry. Glycidyl methacrylate (GMA) in particular, is a bifunctional epoxy resins that can be biosourced. Modification of GMA with unsaturated polyester (UP) from recycled PET is used to form a denser network and increase the mechanical properties of GMA resins. Bottle grade PET is recycled via glycolysis with diol (1,3-propanediol or 2-methyl-1,3-propanediol). UP is synthesised from recycled PET, citraconic anhydride and diol. Semi-crystalline UP (UPsc) is obtained from 1,3-propanediol and amorphous UP (UPam) from 2-methyl-1,3-propanediol. Both UPs are characterised by a double C=C bond and -OH and -COOH end chains. The first curing step forms a 2D-network by radical polymerisation of the ethylene bonds of GMA and UP. The second step is the opening of the oxirane group via ring-opening mechanism with the UP end chains. Polymerisation is initiated with benzoyl peroxide and accelerated with N,N-dimethylaniline. Characterisation methods used in this work were thermal (DSC, TGA), spectroscopic (FTIR, Raman), surface (microscopy) and mechanical (traction) analysis. These methods were used to analyse UPsc, UPam and GMA, to understand the polymerisation mechanism, to establish a suitable curing cycle and to optimise the system. The optimised curing cycle of the resin was evaluated to be a first step of gelation at 45°C for 6 hours, a cure at 100°C for 2 hours and a post-cure at 180°C for 1 hour. Amorphous UP manifested better thermal and mechanical properties than semi-crystalline UP. The system shows environmental and economic interest by valorising the POST-C PET and producing a biosourced material.