A new inmould painting process to produce tractor engine covers recently went into operation at Harita TVS Technologies Ltd., Bangalore, India. The covers, made of fibre-reinforced PUR in a LFI process, are given their high-gloss surface finish inmould. Harita is the world's first PUR processor to use this technique in series production.
The LFI process differs from other PUR processes in that the long glass reinforcing fibres are wetted with the PUR in the mixing head. In recent years, this technique has proved a resounding success. What makes the Harita system strikingly innovative is the fact that the high-gloss surface to the LFI parts is achieved by spraying the paint directly onto the surface of the mould. A barrier coat is applied between the paint layer and the LFI substrate to prevent the glass fibres spoiling the smoothness of the paint surface.
Successful endurance tests - 12,000 hours in agricultural operation - have shown that the engine covers are rugged and long-lasting. They can withstand temperatures up to 100°C and have outstanding mechanical properties. The new production process has other advantages, for instance, exact colour matching of the engine covers and the injection moulded frontend, as well as the possibility of integrating metal inserts in the production process.
Applications for inmould painting for LFI include parts for buses, construction machinery, agricultural vehicles and boat building.