New coating saves paint
12 Nov 2001
US-based BASF Coatings has developed DynaSeal, a new type of coating for fibre-reinforced plastics that are used as sheet mould compounds (SMC) in the production of moulded exterior car body panels.
The new coating is cured in a dual process that combines exposure to UV light and a thermal cure.
SMC is extensively used in automotive applications because of its favourable weight-to-strength ratio and ability to be moulded into complex parts such as tailgates, hoods and fenders.
However, due to 'out-gassing' of volatile materials from the substrate during the curing process, SMC has been difficult to paint with standard coating systems that are cured only thermally; it also require several process steps. Since this process causes defects on the surface of moulded parts and leads to high repair rates, SMC's viability for use in exterior class A body panels was limited.
'DynaSeal prevents 'out-gassing' by sealing the SMC surface,' explains Ray Nix, Director of Sales and Services, Automotive Components for BASF Corporation's Automotive OEM Coatings Regional Business Unit.
'This is achieved by curing the coating with UV radiation before the thermal cure. The result is a coating that stands out for good adhesion and stone chip resistance. The UV rays seal the surface of SMC materials before they undergo the thermal cure.
The polymerised film prevents 'out-gassing' from the part when the subsequent paint layers are cured.' In short: 'DynaSeal enhances the suitability of SMC materials for use in the automotive industry.'
BASF currently supplies DynaSeal coatings to Meridian Automotive Systems' facility in Kansas City, Kansas. At this location, more than 700 SMC rear fenders are coated each day using the new process. They are then shipped to the nearby assembly plant of Ford Corporation. At the Ford plant, the fenders are then used in the production of pickup trucks.
Prior to the use of this product, an in-mould coating was used at Meridian to coat the SMC rear fenders that was delivered at 5 mils film thickness. DynaSeal is used at 1 mil film build, which results in paint savings of up to 80 percent.
