Expanding agents

Expanded polystyrene. The plastic is formed into beads containing an expanding agent. When placed in a mould and heated they swell and stick together. The blocks are then cut into thicknesses as required. 

It was possible to cover additional applications with these new types. In 1951 BASF found it was possible to impregnate polystyrene direct with expanding agents in the suspension process. This opened up great new possibilities for polystyrene foam (STYR0P0R, BASF, 33), for example in the packaging and building fields. 

A material, such as (a) a terpolymer of propylene, ethylene and butene-1, (b) a polyolefin composition, which includes about 31 to 39% of a copolymer of propylene and ethylene and about 58 to 72% of a terpolymer of propylene, ethylene and butene-1 or (c) a polyolefin composition, which includes about 30 to 65% of a copolymer of propylene and butene-1 and about 35 to 70% of a copolymer of propylene and ethylene, is irradiated and extruded through a die in the presence of a physical expanding agent and a cell nucleating agent to produce a structure having a density, which is at least 10 times less than the initial density of the material. The foam articles exhibit improved flexibility and low temperature toughness compared to conventional propylene polymer materials. 

After degassing the unreacted monomers, the remaining sulfur dioxide can be removed by washing the beads with water. After drying, the beads contain 6-7% hydrocarbons as expanding agent. 

Degussa AG Polystyrene, expandable beads Styrene Expanding agent is fed into the reactor during batch-polymerization 2 1990... 

Pelaspan [Dow], TM for a series of expandable polystyrenes in bead or pellet form. Each bead contains its own expanding agent, which is activated by heat. 

Glues or pastes are adhesives with relatively high viscosity based on animal and/or plant elements (probably mixed with synthetic elements) using water as solvent, respectively, expanding agent. 

Extrusion coating of textile with formulation containing dual expanding agents. [Data from Desai,D.R., us Patent 6,495,206, Dec. 17,2002.]... 

This method was eminently suitable for the determination of volatile expanding agents present in expanded cellular grades of polystyrene. Normal and isopentane are commonly used for this purpose. The method quoted next enables these and wide range of other volatiles to be determined in polystyrene with a reasonable degree of accuracy. 

Figure 8.1 Gas chromatogram of expanding agents liberated from expendable PS at 200 °C for 15 minutes in helium. Chromatographed on 3 m x 5 mm id, 25% di- -butyl phthalate on 44/60 celite aqt 40 °C and 50 ml/min helium flow, with thermal conductivity detection Reproduced from Crompton and Myers, Plastics and Polymers [2]...

Volatile constituents are, however, sometimes encountered, viz expanding agents, plasticizers, lubricants, adhesives, solvents, monomers and degradation products of additives or of the polymer itself and infrared gas cell techniques can be of value in the examination of gas chromatographic fractions containing these types of substances. 

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