Physical And Mechanical Characteristics of Polyurethane Foam Insulators Blown By HFC

Polyurethane foams are widely used as insulation in many industrial fields, especially for the cryogenic fields that require good thermal insulating performance. The very low thermal conductivity of polyurethane foam is due to closed cells containing blowing agents such as chlorofluorocarbons (ex. CFC- 11). CFC-11 has been widely used as a blowing agent thanks to its low thermal conductivity and stability. But CFC-11 depletes the ozone layer in the stratosphere (ODP=1.0) and its use has been prohibited in the leading countries since 1995. Its alternative, HCFC-141b, also depletes the ozone layer although it has a much lower ozone depletion potential (ODP=0.15). So its use will be prohibited from 2005 in the leading countries. Much effort and studies have been made about alternative blowing agents and cellular materials blown by alternative blowing agents. This paper deals with polyurethane foams (PUFs) and reinforced polyurethane foam (R-PUF) blown by HFC-365mfc (ODP=0) and shows their physical properties and mechanical strengths at ambient temperature, especially at cryogenic temperature. PUF is used as an insulation for LNG storage tanks and R-PUF is used as an insulation for cargo containment in LNG ships. Compressive strength, tensile strength and shear strength were measured. Insulation performances such as initial and aged thermal conductivity and the thermal conductivity curve between the temperature range of - 160~20°C were measured. Besides, closed cell content, thermal stability at cryogenic temperature, and cell morphology were measured. PUFs and R-PUF blown by HFC-365mfc showed good stability at cryogenic temperature, good thermal properties and mechanical strengths at ambient and cryogenic temperature. From these test results, it seems to be possible to use PUFs blown by HFC-365mfc as the main insulating material for LNG tanks and LNG cargo containment.