Performance of Carbon Black-Containing Polyurethane Foam in Domestic Refrigerators

Abstract

The North American appliance industry has been challenged to meet stringent federal standards for energy consumption using CFC alternatives, which generally increase thermal conductivity of a foam. After a period of evaluating several options, the industry has, for the most part, settled on hydrochloro-fluorocarbon, HCFC-141b, as a substitute for CFC-11. Studies have shown that appliance foam systems using carbon black in conjunction with HCFC-141b lower k-factors by 6-9% both in panels and in cabinets. Recent efforts in this area have demonstrated that this approach not only lowers k-factors but can provide benefits to reduce energy consumption of refrigerator cabinets. Preliminary evaluation of carbon black-containing foams based on HCFC-141b had shown that the material processed well in cabinets and had no effect on linear appearance. No modifications to the foam processing equipment was necessary. Since black dispersions are relatively higher in viscosity compared to conventional isocyanates, a process study was conducted to understand flow behavior and maximize foam performance in cabinets. Handmix work was extended to cyclopentane systems. Studies have shown that improvements of 7-9% in k-factors can be obtained in foams containing carbon black. This work demonstrates the versatility of using carbon black with different blowing agents. The use of carbon black provides an additional means of improving thermal insulation of polyurethane foam produced with current technologies.