Photoinduced insolubilization of SBS–acrylate films of high thickness under 405 nm

Photosensitive styrene–butadiene–styrene formulation was prepared for flexographic plate production. Real-time FTIR analyses of 500 μm thick samples were performed and polymerization reaction was followed from overtones of acrylate and SBR unsaturations. Photo bleaching studies of photoinitiator revealed that the optimum concentration is 1.6 p (0.98 wt%). In spite of the high viscosity of the resin, the termination mechanism in the SBS acrylate resin was found to be bimolecular. The oxygen inhibition was eliminated with the addition of triphenylphosphine (TPP), each TPP molecule consuming one oxygen molecule. It is shown that the curing of thick samples is homogeneous over the whole thickness of the samples. This is confirmed by dynamic mechanical analysis of the SBS–acrylate mixtures which revealed that a homogeneous network of acrylic and styrenic segments is much more significant as the illumination dose increases.

► Curing 500 μm thick films were homogeneous over the whole thickness.
► Optimum photoinitiator concentration was determined.
► Oxygen inhibition was eliminated with addition of TPP.