Effects of liquid-type silane additives and organoclay on the morphology and thermal conductivity of rigid polyisocyanurate-polyurethane foams

This article investigates the effects of liquid-type silane additives and organoclay as a solid-type additive on the morphological, mechanical and thermal insulating properties of polyisocyanurate-polyurethane (PIR-PUR) foams. The organoclay likely acted as nucleating agents during the formation of PIR-PUR foams. When the liquid silane additives and organoclay were added, the cell size and thermal conductivity of the PIR-PUR foams appeared to be decreased. However, organoclay did not contribute to reduce the cell size distribution of the foam. PIR-PUR foams synthesized with tetramethylsilane as a liquid-type additive showed a smaller average cell size and lower thermal conductivity than that of PIR-PUR foams synthesized with the other silane additives or with organoclay as a solid-type additive. For the PIR-PUR foam with organoclay/TEMS (1.5/1.5 php) mixture, cell size and thermal conductivity of the foam showed similar to the foam with TEMS. These results suggest that smaller cell size appears to be one of the major factors in the improvement of thermal insulation properties of the PIR-PUR foams. Silane additives did not seem to have a strong effect on the flammability of the PIR-PUR foams. However, heat resistance was more dominant for the foam with the organoclay at the higher temperature.