Effects of thiol additives on urethane acrylate UV primers for SMC applications
2009 (English)In: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 64, no 2-3, 238-246 p.Article in journal (Refereed) Published
Sheet molded compound (SMC) is a highly filled, glass fiber reinforced, thermoset material used in trim and body panel automotive parts. When SMC-substrates are coated with conventional thermally cured paints, inherent porosity and entrapped volatiles of the substrate result in popping ("paint pops") defects. UV-curable primers (UVP) provide an order of magnitude reduction of paint defects in SMC coatings, but typically have poor adhesion. Mercaptan polymers have a long history, dating back to 1928. of use in adhesives and sealant applications. The present study investigates a series of UVPs, showing the effect of resin functionality and thiol functional additive content on the adhesion of the coatings to SMC substrates. The SMC formulation is also considered when evaluating UVP adhesion, regarding variables such as surface chemistry, morphology, and surface area. The present study brings to light how adhesion of acrylate UVP can be enhanced with mercaptan moieties in additive amounts. The effect is most apparent on SMC substrates that have been treated to expose inorganic fillers as opposed to untreated surfaces of polyester. Additionally annealing the films boosts adhesion, but only in thiol containing formulations. This is a result of the decrease in T(g)s and modulus of the films with the addition of mercaptans, thus providing better contact with the substrate in comparison to non-thiol containing formulations.
Place, publisher, year, edition, pages
2009. Vol. 64, no 2-3, 238-246 p.
SMC primer, Urethane acrylate radiation cure films, Mercapto adhesion, applications, mold release agent, composites, cure
IdentifiersURN: urn:nbn:se:kth:diva-18198DOI: 10.1016/j.porgcoat.2008.08.031ISI: 000263634300021ScopusID: 2-s2.0-58349103294OAI: oai:DiVA.org:kth-18198DiVA: diva2:336244
QC 201005252010-08-052010-08-052016-04-22Bibliographically approved