Adhesion of photocurable acrylates to solid polymer substrates

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Abstract

The adhesion of a hydrophilic (surface tension γ ≈ 40 mj/m2) and a hydrophobic (γ ≈ 30 mj/m2) photopolymerized acrylate lacuer a low-density polyethylene, polystyrene, polycarbonate, polymide-6-6, polyvinylchloride, polyethyleneterephthalate, poly-(1,1)-difluoroethylene, and polymethylmetacrylate has been investigated. A primary condition to obtain sufficient adhesion, as probed by the Scotch tape test, is that the surface tension of the lecquer has to be lower than the critical surface tension of the lacquer. There is no obvious correlation with possible doner/acceptor interactions between lacquer and substrate. Even when spreading occurs, other factors may cause insufficient adhesion. On polyamide, residual moisture on the surface is vary detrimental to adhesion. Extending the lag-time between application and curin reduced adhesion, in particular to polymers containing aromatic groups. This appears to be due to inhibition of the polymerization reaction by radiation-adsorbing aromatic groups in the swollen interphase. The effect can be avoided by proper choicd of initiator and radiation-adsorbing aromatic groups in the swollen interphase. The effect can be avoided by proper choice of initiator and radiation source. Curing of the lacquers in a nitrogen atmosphere generally results in poor adhesion because the rate of polymerization/curing becomes very high compared with rats of relaxation of stresses in the lacquer.

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