Polystyrene food-packaging

Miltz, J., Elisha, C Mannheim, C. 1980. Sensory threshold of styrene and monomer migration from polystyrene food packages. J. Food Processing and Preservation. 4 281-289. 

Solution Based Recycling of EPS (Expanded Polystyrene), Food Packaging Bulletin 7(7, 8), pp. 13-14, July/Aug. 1998. 

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. 

Methylpentene polymer, a light plastic, has a crystalline melting point of 464 retention up to 392° F, transparency of 92%, and electrical properties similar to fluoroethylene. Its impact strength is greater than polystyrene and polymethyl methacr resistant to alkalies, weak acids, and non-chlorinated solvents. It may be injection m< implements for food packaging and preparation, medical care, and non-stick coating ... 

Odor and taste Polystyrene, styrene-acrylonitrile, polyethylene, acrylic, ABS, polysulfone, EVA, polyphenylene oxide, and many other TPs are examples of satisfactorily odor-free. FDA approvals are available for many of these plastics. Food packaging and refrigerating conditions will also eliminate certain plastics. There are TPs and melamine as well as urea compounds that are suitable for this service. 

What properties of polystyrene make it amenable to thermoforming processes to produce food packaging items such as clam shell containers ... 

Styrolux is an example of a nanostructured polymer which is used in food packaging. It is a polystyrene-polybutadiene block copolymer where polymer chains are build up of alternating polystyrene and polybutadiene blocks. These blocks appear as dark lamellae in the TEM image due to the staining of the polybutadiene with OSO4. This structured nanoscale architecture of the pol5mier, which can be controlled during manufacture, allows the optimum combination of impact resistance and transparency. 

Polypropylene (PP) is used in a variety of areas, from snack food packaging to battery cases to disposable diaper linings. It is frequently interchanged for polyethylene or polystyrene. 

High impact polystyrene is widely used as amorphous engineering plastic and in (food) packaging. 

Packaging applications are the most extensive. Meat, poultry, and egg containers arc thermoformed from extruded foamed polystyrene sheet. The fast-food market also accounts for a substantial amount of polystyrene for takeout containers where the insulation value of a foamed container is an advantage. Containers, tubs, and trays formed from extruded impact polystyrene sheets are used for packaging a large variety of food. Biaxially oriented polystyrene film is thermoformed into blister packs, meat trays, container lids, and cookie, candy, pastiy, and other food packages where clarity is required. 

Common applications for polystyrene include packaging, food containers, and disposable tableware toys furniture, appliances, television cabinets, and sports goods and audio and video cassettes. Expandable polystyrene is widely used in construction for thermal insulation. 

Styrene can cause off-flavors in food products packed in polystyrene packaging materials. Each food product has a different sensitivity to styrene off-flavors and thus each food package system needs to be evaluated individually. The formation of styrene off-flavor in a given package/product system can be estimated a priori given the styrene threshold concentration in the food, the initial residual styrene monomer concentration in the packaging material and the desired shelf life. If this information is not readily available then accelerated storage tests followed by a sensory comparison can be carried out to evaluate the potential of off-flavor formation in the product. 

Polystyrene is foamed by swelling with pentane, heating to soften the polymer and vaporize the pentane, and allowing it to expand at atmospheric pressure. Extrusion thus produces foamed sheet and board stock, which are used mainly as thermal insulation in commercial refrigerators and freezers, and also in food packaging, roof and wall insulation, and pipe insulation. 

Fully halogenated CFCs were eliminated in polystyrene foam food packaging and containers. Substitute blowing agents used are either no threat to the ozone or are a 95% improvement over fully halogenated CFCs. Action has been taken such as where PS foam cups now are 100% CFC-free, etc. 

Cedap, (European Consortium of Plastic Applications), was established in 1963 in Monaco. Its main activity is the production of polystyrene sheet for food packaging. Cedap is a division of Siamp-Cedap. 

ILSl Europe Report Series Packaging Materials 1. Polyethylene terephthalate (PET) for food packaging applications 2. Polystyrene for food packaging applications 3. Polypropylene for food packaging applications 4. Polyethylene for food packaging applications 5. Polyvinyl chloride (PVC) for food packaging applications. 

Two of the most important food packaging materials using polystyrene resins are oriented polystyrene sheet (OPS) and polystyrene foam sheet. Together, OPS and polystyrene foam sheet packaging account for nearly 40 % of the polystyrene resins used in food packaging applications in North America. 

OPS is commercially available in 0.13-0.76 mm gauge. The tenter frame process for manufacturing OPS is the most common process used today. A typical tenter frame process is shown in Figure 11.1. Tentered OPS is distinguished from polystyrene blown films (which are also biaxially oriented) in that the tenter frame process can produce heavier gauge films than the blown-film process. Blown films (0.025-0.13 mm) are used primarily in window envelopes, lamination, and printed applications tentered OPS is typically used in thermoformed trays, lids, and containers for rigid food packaging applications. 

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