Processing-structure-property relationship in rigid polyurethane foams

Abstract

Rigid polyurethane (PU) foam is used as a thermal insulating and supporting material in domestic refrigerator/freezers and it is produced by reaction injection molding (RIM) process. There is a need to improve the thermal property of rigid PU foam but this is still a challenging problem. Accordingly, this work investigates the RIM process parameters to evaluate their effects on rigid PU foam's structure and hence property. It has been found that mold temperature is a key parameter whereas curing time has negligible effect on structure of PU foam. Cell size, strut thickness, and foam density have been found very critical in controlling the thermal and mechanical properties. Upper and lower values of 30 to 32 kg/m(3) density are critical to observe contribution of radiation and solid conductivity separately. Finally, PU foam with 160 mm average cell size, 16 mm strut thickness, below 10% open cell content, and 30 to 32 kg/m(3) density allow obtaining better thermal insulation without significant reducing in the compressive strength. The presented work provides a better understanding of processing-structure-property relationship to gain knowledge on producing highquality rigid PU foams with improved properties