Two unique condensation curable silicones, with trimethoxy silyl and isocyanate moieties are evaluated. When formulated with energy cured hydroxyl and acrylate dual functional silicones, these materials exhibit increased shear modulus and rigidity, developing over time even in ambient conditions.
The use of secondary cure pathways in energy cured systems has been practiced for many years. In these systems, a condensation cure mechanism is included in the coating design in addition to the energy cured moieties. Whether a “cure” for shadowing or to improve overall film properties, this technique is well demonstrated. We wanted to explore the usefulness of some of our unique silicones as secondary cure components. We will look at polymers with either trialkoxy silane groups or isocyanato functionality appended to the silicone backbone. We will also use in the formulation silicone polymers with both hydroxyl and acrylate groups. The former will react along the secondary condensation pathway and the acrylate functionality will polymerize in response to light.
The salient structures used in the study are shown in the Figure 1. The value of x is either 10 or 50. The acrylate functionality of the OH ACR materials will react with the photoinitiator, starting a free radical reaction which will polymerize the double bonds of the acrylate group. This reaction will be initiated by radiation and some of the film properties will develop very quickly from this energy cured reaction.
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