I'm getting blisters problem when I'm curing my styrene-butadiene rubber coating (SBR contains high parts of styrene) at temperature > 95 celsius. Thickness of the coating is around 1.5 mm on the cotton fabric. And it is a water-based SBR coating.
Need more info to answer this question... thickness of coating, is it solvent cast coating, if so which solvent... and most importantly the type of curing system.
General rule of thumb is using mixed solvents with different volatilities minimizes blisters, and using vacuum can completely eliminate it.. coming to curing systems, DCP cure system tends to be more blistery than sulphur cure... some times adding fillers can eliminate blisters.
Trapped air could be the root cause of blisters. The air may appear from water vapor, volatiles from the resin, or decomposing by-products. Try to cure the materials under pressure and in vacuum, increase the pressure, check the mould -the grooves should be on top, bottom and side.
Solution based SBR may contain water or other solvent depending on process. Other impurities may be thiol or organometallic compound. I suggest you carry out curing in stages so that any entrapped molecule or catalyst or ther agent will be destroyed. Then the final curing at high temperature can be carried out. Alternatively, as suggested by other you carry out curing in vacuum. In this case raise the temperature slowly.
Further to my earlier answer, I have one more advice. You can heat to the curing temperature under pressure for short while and remove the pressure. Again apply pressure and heat. Do it for 2-3 times and finally cure for remaining period under pressure. Intermittent relieving stress removes the gaseous materials at high temperature when rubber is not only in soft state.
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