Expandable polystyrene physical properties

Expanded polystyrene bead mol ding products account for the largest portion of the drinking cup market and are used in fabricating a variety of other products including packaging materials, iasulation board, and ice chests. The iasulation value, the moisture resistance, and physical properties are inferior to extmded boardstock, but the material cost is much less. 

Expandable polystyrene with improved properties has been obtained by copolymerization, postreaction, additives, or by physical means. Improvements have been achieved particularly in resistance to premature fusion of particles during expansion, in reducing cell size, in self-extin-guishability, in attractive coloration, in resistance of foams to attack by gasoline and in dimensional stability of foams at elevated temperatures. 

Expanded polystyrene foam (EPS) has different applications, because of its physical form (beads) and properties (higher permeability to water and less effective adhesion to facing materials than polyurethane). The expansion gases, pentane and steam, escape fairly rapidly from the foam, so the thermal conductivity of the foam filled with air is about twice that of the best polyurethane foam—a 50 mm thick slab of foam has a U-value of 0.5-0.6 Wm K . EPS mouldings can be used as shutters (formwork) for pouring concrete in a composite wall. The two EPS layers are connected at intervals to fix the thickness of the concrete. Extruded polystyrene foam (XPS) is used in plank form for insulation imder the concrete floor of houses, and in roofing panels. 

The main physical properties of expanded polystyrene foam are dependent on the density as is seen in Table 8. Unlike the thermoset rigid polyurethanes, thermoplastic poly-... 

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