After applying polyester gel coats on glass reinforced composites. we are facing lot of scratching problems and it is increasing the finishing stage of product. If any filler or additives can avoid these scratches on gelcoats?
it appears you are facing shrinkage defects rather than cracks. this may be caused by
a) difference in miscibility of two surfaces
b) difference in intrinsic nature of two surfaces (hydrophobicity and hydrophilicity)
c) difference in angle of wetting of two materials
d) difference in coefficient of thermal conductivity of two surfaces
point (d) is most unlikely to happen
you can consider block copolymers which can modify hydrophillic or hydrophobic nature f two surfaces.
i hope this helps!
I also think that you have no scratches but surface defects caused by problems of incompatibility.
Polyester gelcoats are based on the chemistry of UP resins (unsaturated polyester). The composits are in most cases epoxy resins so that compatiblity and adhesion are not optimal. I would suggest to add glycidyl methacrylate as additive. It can copolymerize with the UP coating and the epoxy groups can give a coupling to the epoxy resin composit. For additives with the character of surfactants (better compatiblity of different surfaces) you can look at www.byk.com .
@Burkhard and @Ali. Its not a compatibility issue, because gel coat and resin are polyester based. The problem is after demolding article from mold there are several operations like trimming, assembly and finishing and packing. From start to last we are phasing some scratches it came because of handling. these scratches are increasing our process time for manufacturing. My question is is there any additive or film to avosd these kind of handling scratches on gel coat.
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