Pentane blowing agents

Expandable polystyrene (EPS) is a specialized form of plastics, which usually includes a pentane blowing agent, used to make low densities of 0.75 to 10 Ib./ft. of foam shapes and blocks. Different-sized pellets provide changes in density. These materials are well suited for thermal insulation and energy absorption. Various different formulations exist such as ones with improved heat tolerance, solvent resistance, and cushioning abilities. 

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). 

Bead Processes. These processes have generally replaced the above techniques. The styrene is polymerised by bead (suspension) polymerisation techniques. The blowing agent, typically 6% of low boiling petroleum ether fraction such as n-pentane, may be incorporated before polymerisation or used to impregnate the bead under heat and pressure in a post-polymerisation operation. 

STYR0P0R, BASF - polymerization of styrene monomer in suspension in the presence of pentane as the blowing agent. Manufacture of new insulating packaging materials, etc. Suspension polymerization of crystal polystyrene in Ludwigshafen. 

The pentane (or other hydrocarbons) used as the blowing agent is highly inflammable and fire regulations must be considered for transport, handling, storage, processing... 

The process is commonly used to mould expandable polystyrene (EPS) that is delivered containing some percentage of pentane as the blowing agent. The moulding needs three steps ... 

The blowing agent can be a hydrocarbon (pentane, for example), which is easily flammable, and precautions against fire must be taken at all the stages of transport, handling, storage, manufacture... 

For the above-mentioned reasons the performance of this procedure is not quite simple in the context of a practical course.Therefore the following instruction is intended only to experimentally demonstrate two effects dissolving of pentane in solid polystyrene and foaming of the polystyrene, containing a blowing agent, in hot water. 

Sulphur is essential in the usual processing technology of rubbers it brings about the formation of cross-links , which provide the necessary shape stability. Pentane is a blowing agent, applied in a.o. PS, to form foam. 

Another possibility is to extrude foam into sheets the pressure within the extruder prevents foam formation only after leaving the die the pentane evaporates to form the foam. In most cases the extrusion process is carried out with normal PS granules in the cylinder pentane or another blowing agent is injected, where it mixes into the polymer and brings about foam formation after leaving the die. 

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