Insulation rigid polyurethane foam, effect

The Effects of Regulatory Actions on the Marketing of Rigid Polyurethane Foam Insulation... 

Prociak [49] studied the effect of the method of sample preparation, the temperature gradient, and the average temperatnre of measnrement on the thermal conductivity of rigid polyurethane foams blown with hydrocarbons and hydrofluorocarbons. The thermal insulation properties of different cellular plastics, such as rigid and flexible polyurethane foams, as well as expanded polystyrene, were compared. The thermal conductivity and thermal diffusivity of foams were correlated with the polyurethane matrix structure to demonstrate the effect of cell anisotropy on the thermal insulation properties of the rigid foams blown with cyclopentane and HFC-365/227 (93 wt% pentafluorobutane/7 wt% heptafluoropropane). 

Rigid polyurethane foams are closed-cell structures which are usually produced with a density of about 2 Ib/ft. Since the major interest in rigid foams has been for thermal insulation, the thermal conductivity of the foams is a physical property of some importance. About 97% of the volume of a typical foam is occupied by gas, the nature of which therefore has an appreciable effect on the thermal conductivity. This point is illustrated by Table 14.4 which shows the conductivities of various gases and foams. Newly made carbon dioxide-blown foam has low conductivity but the carbon dioxide rapidly diffuses through the polymer and is replaced by air the conductivity therefore increases until it reaches the value for air-filled foam. Trichlorofluoromethane diffuses very slowly and an equilibrium appears to be reached when the air to fluorocarbon in... 

Rigid polyurethane foams are widely used in various fields as insulation materials, packing materials and stmcture materials. Rigid polyurethane material is formed into various shapes of foam by many kinds of molding. As a result, cell shape becomes very complicated. Gibson shows that the shape anisotropy-ratio has an effect on the mechanical properties of foam. The previous reports by the authors showed that the cell shape was suggested to approximate the oval and the compressive behavior of the foam has been analyzed " l... 

Difluorochloro-ethane (CH5CCIF2) An effective replacement for CFC-12 in rigid polyurethane, polystyrene, and polyethylene foam insulation applications. Uses include both residential and commercial construction and process piping. 

We have already been introduced to polyurethane chemistry in Chapter 10, Section 2, where we used toluene diisocyanate (TDI) reacting with a diol to give a polyurethane. Polyurethanes derived from MDI are more rigid than those from TDI. New applications for these rigid foams are in home insulation and exterior autobody parts. The intermediate MDA is now on the Reasonably Anticipated to Be Human Carcinogens list and the effect of this action on the market for MDI remains to be seen. The TLV-TWA values for MDA and MDI are some of the lowest of the chemicals we have discussed, being 0.1 and 0.005 ppm respectively. 

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