Foamed plastics blowing agents

Wfl-Foam. [Akzo Engineering Plastics] Blowing agent cones. 

Keywords recycling, cross linking, compression molding, plastics foaming, chemical blowing agents. 

The use of CFCs as foam blowing agents has decreased 35% from 1986 levels. Polyurethanes, phenoHcs, extmded polystyrenes, and polyolefins are blown with CFCs, and in 1990 the building and appHance insulation markets represented about 88% of the 174,000 t of CFCs used in foams (see Foamed plastics). 

Research and development programs have been initiated by the cellular plastics industry to develop viable substitute blowing agents. These must have similar or improved properties to their CFC counterparts at a reasonable cost. Emphasis was initially placed on HCFC 123 and HCFC 141b, both having much shorter lifetimes and considerably less effect (up to 50 times) on o2one layer depletion (22). However, various options, including gas mixtures, water, or CO2 blown foams, continue to be studied ultimately to eliminate all CFCs and HCFCs. 

PS Foams. The eady history of foamed PS is available (244), as are discussions of the theory of plastic foams (245). Foamable PS beads were developed in the 1950s by BASF under the trademark of STYROPOR (246—248). These beads, made by suspension polymerization in the presence of blowing agents such as pentane or hexane, or by post-pressurization with the same blowing agents, have had an almost explosive growth, with 200,000 metric tons used in 1980. Some typical physical properties of PS foams are Hsted in Table 10 (see Foamed plastics). 

Plastics. Citric acid and bicarbonate are used as an effervescent blowing agent to foam polystyrene for insulated food and beverage containers replacing blowing agents such as chlorinated fluorocarbons (194—206). 

The following materials serve as ingredients for foam plastics the polymers, blowing agents, hardeners, plastifiers, lubricants, stabilizers, fillers, and other substances. 

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