Expanded polystyrene foam

Polystyrene, as mentioned, is the most common packaging foam. Polystyrene foam is the material of choice if it can perform acceptably, since it is typically the least expensive packaging foam available. It is used extensively for containers as well as for cushioning material, in molded shapes and in extruded form. Molded shapes are commonly termed expanded polystyrene foam (EPS), while the extruded material is called simply extruded PS foam. The term styrofoam is often incorrectly used for these materials, but Styrofoam is a Dow Chemical Company trade-marked extruded polystyrene foam used primarily for building insulation and not found in packaging. 

PS foam is relatively chemically inert, and is acceptable for use in food packaging. PS foam trays are widely used for meat and produce. The ubiquitous coffee cup utilizes the light weight of PS foam combined with its insulating ability to provide an inexpensive container for hot drinks. Fast food outlets often use PS foam in the shape of bowls or clamshells for products that need to be kept either hot or cold. Shippers of sensitive products ranging from fish to pharmaceuticals often rely on PS foam containers to keep products cold during distribution, especially if the products are shipped by air freight. 

The mold can directly produce the final shape desired, or it can simply produce a block of material that is subsequently cut into the final shape. Additional aging and curing steps may be employed to further reduce the density of the material. 

Expandable PS beads are manufactured in three sizes small, medium, and large. The bead size required depends on the wall thickness of the molded part. Large beads can be used for thick walls, while small beads are necessary for products with thin walls. 

Adhesive-coated expanded PS shapes have been used as an alternative to foam-inplace polyurethane systems (see Section 13.1.3). The shapes are deposited into a corrugated box, covered with a release film, the product added, another sheet of release film put in place, and the carton filled with the adhesive-coated shapes. When the water-based adhesive dries, a pair of resilient cushions surrounds the product. 

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In another appHcation expanded polystyrene foam panels, 1.2 x 2.4 m, are faced with a wire mesh and mounted ia a metal channel bolted to a coacrete slab. These panels are then sprayed on both sides with plaster, which is anchored to the wire mesh and forms the iaterior and exterior surfaces. Roof and iaterior partitioas provide low cost housiag for mild climates. 

The most important use of polystyrene is in packaging. Molded polystyrene is used in items such as automobile interior parts, furniture, and home appliances. Packaging uses plus specialized food uses such as containers for carryout food are growth areas. Expanded polystyrene foams, which are produced by polymerizing styrene with a volatile solvent such as pentane, have low densities. They are used extensively in insulation and flotation (lifejackets). 

The magnet is driven by a magnetic stirrer motor on which the vessel stands. Traditional magnetic stirrers when running for long periods create excessive heat and the vessel requires to be insulated by having a sheet of expanded polystyrene foam interposed between it and the motor. Bellco spinner flasks (Fig 3.6) are available from Arnold Horwell Ltd. (Appendix 3). 

Other styrenic polymer foams were developed in the mid-1950s through the early 1960s. Examples are molded expanded polystyrene foam (MEPS), extruded polystyrene foam sheet, and expanded polystyrene loose-fill packaging material. 

The Steiner Tunnel test (ASTM E 84) is used to classify the fire-spread potential of products used in wall and ceiling linings [4], and is used to classify expanded polystyrene foam. In this method, specimens are placed on the ceiling of a 24 ft long tunnel. An 88 kW natural gas burner is placed at one end of the tunnel and a forced-air draft with a velocity of 1.22 m/s is introduced. The flame spread is recorded as a function of time and an arbitrary index is calculated from the measurements. 

Because expanded polystyrene foam is processed at a lower temperature, aliphatic bromine compounds such as hexabromocyclododerane (HBCD) can be used for this application. The flame retardant levels in these systems are family low, typically less than 3wt%. These levels are sufficient to pass the Steiner Tunnel test, and synergists such as antimony trioxide are not necessary. 

HBCD is the most widely used flame retardant for expanded polystyrene foam. 

Tetrabromobisphenol A bis(allyl ether) finds some utility in expanded polystyrene foam. 

Flame-retardant styrenic polymers find utility in applications such as building insulation (expanded polystyrene foam) and electronic enclosures (flame-retardant HIPS, ABS and styrenic blends). The most effective flame retardants are halogen-(particularly bromine)-containing compounds these flame retardants act by inhibiting the radical combustion reactions occurring in the vapor phase. Flame-retardant plastics are in a state of flux, due to influences of... 

Expanded polystyrene foam known commercially as Styrofoam, is sold in blocks and sheets for building model airplane wing cores.These are available from hobby shops or by mail from model supply houses. Numerous shapes including balls,cones,rings etc.are sold for flower decgrating and general craft use. These are found in any variety store. Fpam packing containers may be picked up from department stores,usually for free. 

Solid Gas Solid foam Polyurethane or expanded polystyrene foams... 

Amerpac. [Drew Ind. Div.] Recyclable semibulk containers consisting of HOPE on expanded polystyrene foam cushioning and protected by galvanized steel outer shell. 

Unsaturated polyester, rigid polyurethanes foam, expandable polystyrene foam... 

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. 

Fig. 12. Activation spectrum for change in yellowness index of extruded, expanded, polystyrene foam on exposure to a filtered xenon source (189 h exposure at 50 Q determin by the cut-on filter technique [122]...

Expanded polystyrene foam first introduced dy Dow chemicals... 

Expanded polystyrene foam (EPS) is much less denser than seawater. 

Styrofoam (Dow Chemical Co.) is the tradename for expanded polystyrene foam. It is made by a process similar to the one described for foamed polyethylene. The materials have a closed-cell structure with very low thermal conductivity and low moisture absorption. One of the serious limitations of polystyrene foam is its rather low maximum operating temperature of approximately SO C. It is used mainly as thermal insulation in buildings, flotation apparatus, decorations, and packaging. 

Expandable polystyrene is the usual name for the beads used to make molded polystyrene foam parts. Parts made with these beads are usually made in a two-step process. The first step consists of pre-expansion of the beads by heat. After this step, the beads are stored for 6-12 h to allow them to reach equilibrium. The beads are then conveyed to the mold, where they expand to the final dimensions. Steam is the preferred mode of heating, either by introducing live steam through perforations in the mold or by the means of steam probes, which are withdrawn as the beads are expanding. Expandable polystyrene foam can be distinguished from expanded polystyrene foam by the round bead outlines on the surface of the part. The expanded foam has a smooth surface. 

Expanded polystyrene foam is used for thermal insulation and as a packaging material. It is often used for food trays. Polystyrene can also be crosslinked. Cross-linked polystyrene parts are often used in low-loss electrical and electronic applications requiring moderate resistance to temperature. 

Celluliner, Resilient expanded polystyrene foam, Gilman Brothers Co. 

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