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PFA coating for lowest surface roughness on aluminum mould for flexible PU foam |
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Perfluoroalkoxy (PFA) coating produces the lowest surface roughness on aluminum mould for flexible PU foam and thus can save material wastage due to absence of sticking.
Flexible Polyurethane Foam (FPF) is mainly used in automotive industry. One of the problems during production is sticking of the product to the mould. This causes damage to the product when the final product is being taken out from the mold in RIM process. This increases the cost due to higher material wastage and lower production. Normally, the mould is used with bare aluminum and a releasing agent like paraffin wax. For every shot, the releasing agent must be sprayed into the mould.
Fluoropolymers such as PTFE, fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA) and ethylene-tetrafluoroethylene (ETFE) are known to have excellent chemical resistance to acids, bases and solvents and they have good mechanical properties, high temperature stability, self lubrication and non stick properties. Excellent hydrophobic and anti-wear coatings on the surface of metal substrates due to their ability of reducing the macro contact friction under the overall pressure and pollution on the surface of the coating can be one of the possible remedies.
PTFE is a hydrophobic material with a water-contact angle of 108 degree. The contact angles of the FEP and ETFE are 113 degree and 9 degree. Copolymers of tetrafluoroethylene with other fluorinated monomers such as hexafluoropropylene and perfluorovinylether show similar chemical and physical properties to PTFE. However they also show easy fabrication because of low crystalline structure. PTFE has inherent non stick properties due to its low surface energy.
A recent study showed that PFA has the least value of surface roughness and ETFE has the highest one in the four different coatings evaluated. PFA exhibits the best non-stickiness in the contact angle measurements. Results of adhesion test indicate that ETFE coating exhibits low adhesion behavior. PFA shows the least adhesion value in the adhesion behavior test between Al surface and the coating.
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