Reinforcement of silicone cushions using silica fillers

Cushions prepared with fillers pretreated with wetting agents were much easier to process in all stages of production except for sheeting prior to bin aging. However, the use of these pre-wetted fillers resulted in an unacceptable increase in compression set. The processability of cushions containing fillers integrally treated with either wetting or coupling agents was no different from that of cushions containing untreated fillers. However, cushions prepared with the integral addition of a vinyl coupling agent did not show the increase in compression set that was so prevalent in the cushions made with pre-wetted fillers. This suggests that pretreating the fillers with coupling agents may improve the processability without cost to the final cushion properties. The data collected indicated that the use of Hi Sil with these surface modifiers appears to have no effect apart from altering the total filler loading. Y1587 not only softens the final cushions, it also appears to contribute significantly to the compression set. The ease in handling pretreated fillers could eliminate the need for a processing aid like Y1587, thus providing a possible means for reducing compression set.