Zero Emission In-Mould Gel-Coating
for polymer composites
In many applications of fibre-reinforced polymer matrix composites, a separate surface finish for cosmetic and/or durability reasons is required. Traditionally the coating is painted or sprayed onto the open mould before the structural laminate is moulded. The majority of such composites have an unsaturated polyester resin matrix which releases styrene (a volatile organic compound which acts as a reactive diluent) vapour leading to an unpleasant working environment and potential odour nuisance at the factory boundary. Styrene has been the subject of extensive debate in respect of health and environmental issues. Forthcoming styrene risk assessments by the European Union are expected to be the major driver in the near future regarding styrene classification, labelling and use.
This project aims to help the UK composites industry to remain competitive, to improved workplace conditions, to reduce environmental impact and hence to be prepared for future legislation regarding styrene emissions. Current IMGC systems rely on controlled mould opening to create a gel-coat cavity after partial resin cure. This increases the complexity of the tooling and limits the geometry of moulded parts to those having low moulding angles. A novel method of applying the coating in a closed mould is being developed using a patented separation layer. This should virtually eliminate all styrene emission to atmosphere. Successful development of this technology would be applicable to current resin transfer moulding operations with minimal capital outlay and would assist and encourage moulders currently using open mould manufacturing methods to move to closed mould resin transfer moulding methods. Our studies indicate that this method would replace the current labour intensive process with one requiring minimal labour thereby providing significant economic incentives. The research consortium is aware that the developing economies such as China, India and the Far East are already looking at moving to closed mould manufacturing methods so our innovation improves the ability of UK industry to compete.
A flat panel mould is in use at Plymouth to trial different spacer fabrics, gel-coats and other process variables using RTM and RTM-light processes. The panels are then subjected to surface finish analysis and interface bond strength testing. A dome mould is being used at MVP to assess the use of this technology on curved components. Other partners will use the technology for demonstrator components.
The project was funded by the UK Technology Strategy Board under the Technology Programme for Collaborative R&D call: Meeting the Challenge of the Zero Emission Enterprise (ZEE). Project partners were:
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Publications arising from this project and associated work:
Test mould for gel coating trials
Microscope image of gelcoat-to-laminate interface