Fluorocarbon blowing agents

The thermal conductivity of a cellular polymer can change upon aging under ambient conditions if the gas composition is influenced by such aging. Such a case is evidenced when oxygen or nitrogen diffuses into polyurethane foams that initially have only a fluorocarbon blowing agent in the cells (32,130,143,190,191,198-201). 

In the prepolymer method for one-shot polyether flexible urethane foams the primary role of the silicone surfactant is to lower surface tension and to provide film (cell-wall) resilience. Resilient films prevent the collapse of the foam during foam rise and continue to stabilize it until the foam is self-supporting. A secondary, but nevertheless important role of the silicone surfactant is cell-size control. The silicones can be added to the formulation in any of the 2 to 6 streams usually fed to the mixing head in the one-shot process. Usually, however, the silicone is metered separately, in combination with the polyol, or added as a wa-ter/amine/silicone mixture. It can also be added in the fluorocarbon blowing agent (52). 

In the foam-in-place process a liquid urethane chemical mixture containing a fluorocarbon blowing agent is simply poured into a cavity or metered in by machine. The liquid flows to the bottom of the cavity and foams up, filling all cracks and comers and forming a strong seamless core with good adhesion to the inside of the walls that form the cavity. The cavity, of course, can be any space, from the space... 

GOR Gorski, R.A., Ramsey, R.B., and Dishart, K.T., Physical properties of blowing agent polymer systems -1. SolubiUty of fluorocarbon blowing agents in thermoplastic resins, J. 

Changing methods to produce flexible foam, by the replacement of fluorocarbon blowing agents in many cases with carbon dioxide, have brought consequences for the choice of flame retardant... 

Dichlorotetrafluoroethane (Freon 114) n. CIF2CCCIF2. A fluorocarbon blowing agent used when a low boiling point (3.6°C) is required. 

Improved compatability with polymeric isocyanate and fluorocarbon blowing agent. 

Low density polyethylene foam products (thin sheets, planks, rounds, tubes) in the range of 32-160 kg/m (2-10 Ib/ft ) have been prepared by an extrusion technique using various gaseous fluorocarbon blowing agents (97,98). The techniques are similar to those described earlier for producing extruded polystyrene foam planks and foam sheets. 

Fluorocarbon Blowing Agent n A family of inert, noncorrosive liquid compounds containing carbon, chlorine and fluorine, originally developed as refrigerants. They are compatible with all resins and leave no residues in molds. For years they were widely used in structural-foam extrusion, in which they were incorporated with the polymer by direct injection through the barrel of the first of two tandem extruders. Fluorinated... 

The poly(alkylene oxide)s are principally used to make rigid foams because they have good hydrolytic stability, are compatible with fluorocarbon blowing agents, and can be obtained with high functionalities, around 3 to 6, and with predetermined hydroxyl numbers (38). The polyols can be obtained by propoxylation of a starter (see Chapter 4, Section IV) such as glycerine (functionality of 3) or sorbitol (functionality of 6) or a number of amines such as ethylene diamine or phenylene diamine (functionalities of 4), with hydroxyl numbers typically in the range of 300 to 500 mg KOH/g (21). 

Figure 13.9 Plots of versus weight percent of fluorocarbon blowing agent in (O) Rexene 143/(FC-12) mixtures and ( ) Rexene 143/(FC-114) mixtures. (Reprinted from Han and Ma, Journal of Applied Polymer Science 28 831. Copyright 1983, with permission from John Wiley Sons.)...

Gorski, R. A., R. B. Ramsey, and K. T. Dishart. 1985. Physical Properties of Blowing Agent Polymer Systems-I. Solubility of Fluorocarbon Blowing Agents in Thermoplastic Resins. 29th... 

Replacement of fluorocarbon blowing agents Group transfer polymerization Differential viscometry 1990s Metallocene catalysts... 

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