Foamed plastics special processes

Rigid polyurethane foams have a special problem when it comes to making a fair statement about their R-values. Essentially, all of these products are expanded with chlorofluorocarbon 11 (CFC-11), which is trichlorofluoromethane. At the time of formation, all of these materials have essentially the same R-value of about 7.5 to 8.0 per inch of thickness. At one time, that is how these products were marketed. The initial thermal resistance, however, changes with time. Where the foamed plastic is exposed to air, the air migrates into the cells, diluting the chlorofluorocarbon gas. The thermal resistance decreases when this takes place. This is a slow process and may go on for years. To the extent that the foam is sandwiched between air impervious skins, the process is all but halted. 

Special Processes. Several more recent developments have opened the possibility of special foam processes that may grow to tremendous importance and perhaps even change the entire concept of foamed plastics. These are structural foam, reaction injection molding (RIM), and syntactic foam. 

Polystyrene is an aromatic polymer made from styrene, an aromatic monomer which is commercially manufactured from petroleum. Polystyrene is commonly injection moulded or extruded while expanded polystyrene is either extruded or moulded in a special process. Solid polystyrene is used in disposable cutlery, plastic models, CD and DVD cases, etc. Foamed polystyrene is mainly used for packing materials, insulation, foam drink cups, etc. Polystyrene foams are good thermal insulators and therefore used as building insulation materials such as in structural insulated panel building systems. They are also used for non-weight-bearing architectural structures. The information on OPF-polystyrene composites is limited. 

Extra high Commercial and industrial occupancies having normal fire load but subject to special risk factors (a) Process risks Aircraft hangars Foam plastics manufacturers Paint manufacturers... 

Foam Production This is important in froth-flotation separations in the manufac ture of cellular elastomers, plastics, and glass and in certain special apphcations (e.g., food products, fire extinguishers). Unwanted foam can occur in process columns, in agitated vessels, and in reactors in which a gaseous product is formed it must be avoided, destroyed, or controlled. Berkman and Egloff (Emulsions and Foams, Reinhold, New York, 1941, pp. 112-152) have mentioned that foam is produced only in systems possessing the proper combination of interfacial tension, viscosity, volatihty, and concentration of solute or suspended solids. From the standpoint of gas comminution, foam production requires the creation of small biibbles in a hquid capable of sustaining foam. 

The type of processing in the melt state, in the liquid state (plastisols or organosols), foams. Plastisols have very special mechanical, thermal and chemical properties due to their high flexibility and the use of large amounts of plasticizers. The particular morphology of foams induces ... 

Dow Plastics is to unveil a new resilient polyolefin foam, Strandfoam, which offers packagers of lightweight electronic equipment and components reduced package size, and savings in materials and shipping costs. Strandfoam is made of a special blend of PE and is produced by a proprietary extrusion process that yields fused strands of closed-cell foam with a network of air channels parallel to the foam strands. Strandfoam provides the required levels of protection with substantially smaller volumes of foam compared to urethane. 

Syntactic foams are less combustible than their chemically foamed counterparts for the same reason. A syntactic foam s fire resistance can be increased using modifiers and additives in much the same way as for ordinary plastics, the only additional precaution being that the filler—binder adhesion should not be impaired in the process. Specially compounded polyester resins have been used in the USSR to obtain syntactic foams, whose combustion times and mass losses are, respectively, 4-60 and 24 to 180 times lower than those of the unmodified plastic 155). 

Uses Pearlescent, opacifier, thickener, lubricant, emulsifier, emollient in cosmetics, emulsion shampoos and foam baths plasticizer, lubricant, antistat for plastics and rubber surfactant in paints, pharmaceuticals w/o emulsifier, dispersant, antistat for textiles, paper processing, cutting oils, polishes, emulsion cleaners, rubber latex, wool lubricants emulsifier, lubricant, antistat, defoamer for metalworking intermediate specialized solvent diluent in food colorants defoamer in food-contact paper/paperboard Regulatory FDA 21CFR 73.1,176.210... 

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