By David Reed, UT EditorLeverkusen, Germany-Bayer MaterialScience claims to have developed solutions allowing the use of rigid polyurethane foams at both extremes of the temperature range.For foams requiring resistance to temperatures as high as 200°C-such as are used in insulating steam pipelines in district heating systems, or pipelines for transporting hot crude oil-the firm offers new polyols which yield polyisocyanurate (PIR) foams with improved physical properties, specifically in terms of their friability or brittleness.The resultant foams can withstand temperatures up to 250°C for short periods, or long-term exposure to temperatures of up to 200°C at densities of between 40 and 130 kg/m3, according to a Bayer statement. They also keep their shape better at these temperatures than foams produced using conventional formulations and, even with pentane as a propellant and no flame retardants, still achieve a B2 flammability classification, the firm claims. "Tank trucks transporting hot goods can now be made lighter while at the same time providing more capacity," says Jacqueline Kusan-Bindels, one of the Bayer scientists involved in the development of the new materials."PIR rigid foam has clear advantages over mineral wool, because the insulating layer takes up less space and insulating the pipe with this rigid polyurethane foam is much more cost-effective than 'stuffing' it with mineral wool," said Joachim Kleser, heat insulation expert at Bayer MaterialScience, in a talk during the Gulf Construction Conference Week 2004 in Dubai, United Arab Emirates.Another solution was required for the foams to be used at very low temperatures, such as in tankers transporting liquid gas, Bayer said. "In the low-temperature range, we have achieved very successful results by combining tough rigid polyurethane foams with glass fibres," said Kusan-Bindels, in the prepared statement. As in high-tech composites, "these strengthening materials prevent the polyurethane foam from becoming fatigued and eventually tearing as a result of repeated heating and cooling," she added.Currently, these giant tankers-which can carry up to 200 000 cubic metres of liquefied gas-are mostly insulated with densely packed perlite beads which take up much more space than sheets of rigid polyurethane foam because they have lower insulating capacity, Bayer points out. "With rigid polyurethane foam that is stable at low temperatures, ocean-going loads can be increased, thereby enhancing cost-effectiveness," Kusan-Bindels concluded."
