Polystyrene packaging

Eoamed polystyrene sheet has exceUent strength, thermal resistance, formabUity, and shock resistance, as weU as low density. It is widely known for its use in beverage cups, food containers, building insulation panels, and shock absorbent packaging. Polystyrene products can be recycled if suitable coUection methods are estabUshed. Eoamed polystyrene sheet can also be easily therm oformed (see Styrene plastics). 

In addition to styrene migration from the primary package, polystyrene containing toys, surprises and other items packed inside a package together with product can also be a source of styrene monomer off-flavor. The polystyrene used may or may not be food grade and the overwrap for the item is usually not a barrier to the transmission of styrene into the food. 

Polystyrene, expandable filling material, loose protective packaging Polystyrene, expandable filling, dental impression compounds Gutta percha filling, electronic tubes Argon... 

Polystyrene packaging housewares luggage radio and television cabi nets... 

The clean, durable, nondust-forrning character of polyethylene foam has led to its acceptance in packaging missile parts (230). Polyethylene foam sheet has also displaced polystyrene foam sheet for packaging glass bottles and containers because of its greater resUiency and tear resistance. 

Economics. Rigid foam systems are typically in the range of 32 kg/m (2 Ibs/fT) and, in 1992, had a foam price of about 3.63/kg ( 1.65 per lb) with hquid foam systems at about 2.75/kg. Unit prices for pour-ia-place polyurethane packaging systems fall between the competitive expandable polystyrene bead foam at 3.30/kg and low density polyethylene foams at 5.80/kg. 

There are five basic types of polystyrene foams produced in a wide range of densities and employed in a wide variety of apphcations (/) extmded polystyrene board (2) extmded polystyrene sheet (2) expanded bead mol ding (4) injection molded stmctural foam and (5) expanded polystyrene loose-fiU packaging. 

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. 

Eresh fmit and vegetable packaging is often in bulk in a variety of traditional wooden boxes and crates, and cormgated fiberboard cases. At or near the retail level, bulk produce may be repackaged in oxygen-permeable flexible materials such as PVC, with or without a tray of foamed polystyrene. 

Hard baked goods such as cookies and crackers have a relatively low water and high fat content. Water can be absorbed, and the product loses its desirable texture and becomes subject to Hpid rancidity. Packagiag for cookies and crackers includes polyolefin-coextmsion film pouches within paperboard carton sheUs, and polystyrene trays overwrapped with polyethylene or oriented polypropylene film. Soft cookies are packaged in high water-vapor-barrier laminations containing aluminum foil. 

Steam-Chest Expansion. In steam-chest expansion the resin beads in which gas is already present are poured into molds into which steam is injected. The steam increases the temperature close to the melting point and expands within the stmcture to create beads with food cushioning and insulating properties. Expanded polystyrene is widely used in this process for thermal insulation of frozen food packaging. 

Conventional thermoforming of polystyrene and PVC is the most widely used technique for making packages for dairy products and for disposable cups and trays. 

Polystyrene (PS). Common appHcations include packaging, food containers, and disposable tableware toys furniture, appHances, television cabinets, and sports goods and audio and video cassettes. For some of these appHcations, PS is modified by blending or graft polymerization with SBR to form impact polystyrene, which is less sensitive to breakage. Expandable polystyrene is widely used in constmction for thermal insulation. 

Commercial polystyrenes are normally rather pure polymers. The amount of styrene, ethylbenzene, styrene dimers and trimers, and other hydrocarbons is minimized by effective devolatilization or by the use of chemical initiators (33). Polystyrenes with low overall volatiles content have relatively high heat-deformation temperatures. The very low content of monomer and other solvents, eg, ethylbenzene, in PS is desirable in the packaging of food. The negligible level of extraction of organic materials from PS is of cmcial importance in this appHcation. 

Impact polystyrenes have found use in the manufacture of refrigerator door liners and in packaging. They are also commonly used for appHance housings, radio and television cabinets, sporting goods, toys, cameras, furniture, luggage, pipe and fittings, automotive parts, and women s shoe heels (96). 

Cheap moulded objects. Toughened with butadiene to moke high-impact polystyrene (FIIPS). Foamed with CO2 to moke common packaging. 

One particular growth area for polypropylene mouldings is for thin-wall packaging such as margarine tubs. This is largely at the expense of polystyrene and arises partly from economics and partly from the wish to have a produet free of residual styrene monomer. 

Because of the excellent gas barrier properties, EVOH is of interest as a packaging material. However, because of its high water absorption it is usually used as an internal layer in a co-extruded film, sheet, bottle or tube. For example, the system HDPE-EVOH-EVA may be used as a barrier film for packaging cereals, and the system polystyrene-EVOH-polystyrene for packaging coffee and cream, whilst the system polystyrene-EVOH-polyethylene has the additional advantage of heat scalability. 

The largest outlet for polystyrene is in packaging applications. Specific uses include bottle caps, small jars and other injection moulded containers, blown containers (a somewhat recent development but which has found rapid acceptance for talcum powder), vacuum formed toughened polystyrene as liners for boxed goods and oriented polystyrene film for foodstuffs such as creamed... 

Nearly all the expanded polystyrene that is not used for thermal insulation is used for packaging. Uses range from individually designed box interiors for packing delicate equipment such as cameras and electronic equipment, thermoformed egg-boxes to individual beads (which may be up to 5 cm long and about 1 cm in diameter) for use as a loose fill material. There is also some use of thin-wall containers for short-term packaging and conveying of hot food from... 

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