Packaging apphcation

Eor high value food packaging appHcations, minimal migration of contaminants into food products is critical. Currently the PDA requirement is a maximum 0.5 parts per biUion (ppb) of noncarcinogenic compounds by dietary exposure (22). 

Thermoforming is used for gauges above 6 mm in some nonpackaging appHcations for packaging appHcations gauges are between 0.6 and 2.5 mm. 

Many polymers, including polyethylene, polypropylene, and nylons, do not dissolve in suitable casting solvents. In the laboratory, membranes can be made from such polymers by melt pressing, in which the polymer is sandwiched at high pressure between two heated plates. A pressure of 13.8—34.5 MPa (2000—5000 psi) is appHed for 0.5 to 5 minutes, at a plate temperature just above the melting point of the polymer. Melt forming is commonly used to make dense films for packaging appHcations, either by extmsion as a sheet from a die or as blown film. 

Blow-molded products represent the biggest use of HDPE resins, at around 40%. Packaging appHcations account for by far the greatest share of this market. These include such products as botties (especially for milk, juice, and soap), housewares, toys, pails, dmms, and tanks. Expected aimual average growth rates for these appHcations are about 5—6%. Injection-molding products are the second largest appHcation, with approximately 20% of the HDPE market. These products include housewares, toys, food containers, pails, crates, and cases. 

Highly branched fractions of nonuniformly branched resins have low molecular weights and are easily soluble, even at room temperature, in saturated hydrocarbons. These highly branched fractions are called extractables, an excessive amount of which in an LLDPE resin can be detrimental to certain end use properties, especially in food packaging appHcations. 

An important property recommending the use of LLDPE in many packaging appHcations is thek sealabHity. CompositionaHy uniform resins are especiaHy attractive for such use because thek melting and softening points are 15—20°C lower than those of commodity LLDPE resins (Fig. 1). 

In particular, PB and PMP are inert materials and usually present no health hazard. PMP is employed extensively for a number of medical and food packaging appHcations. Several grades conform to FDA regulations and to the health standards of other countries. Flammability of polyolefin resins is equal to that of PP, around 2.5 cm /min (ASTM D635). However, during combustion or pyrolysis, smoke, fumes, and toxic decomposition products are formed and can pose a health hazard. 

The web materials used to form dmms and cans can be customized to each packaging apphcation. The materials are selected based on the package properties of moisture and humidity resistance, nonstick resistance, or barrier properties required. The adhesives used to bond the phes together include sihcates, poly(vinyl alcohol), and poly(vinyl acetate) (10). Sihcate adhesives are most commonly used in the manufacture of dmm packages. 

Chromium complexes of long-chain fatty acids are exceUent water repeUents which are also used for their food-release properties in certain packaging appHcations. The presence of chromium has raised environmental concerns, despite the fact that the metal is in the trivalent rather than in the highly toxic hexavalent state. This material is available as Qudon (DuPont). 

Esters of thiopropionic acid tend to decompose at high processing temperatures, and their odor makes them unsuitable for some food-packaging apphcations. 

Cellulose gum is the accepted common name for purified CMC. It may be used in milk products, dressings, jellies, symps, beverages, and other select products. It is permitted in food contact and packaging appHcations. 

Hwo, C., Forschner, T., Lowtan, R., Gwyn, D., and Barry, C. Poly(trimethylene phthalates or naphthalate) and Copolymers New Opportunities in Frhn and Packaging Apphcations, In Shell Chemicals, Proceedings of the Future-Pak 98 Conference, Chicago, USA, November pp. 10-12(1998). lijima, S. Nature, 354,56-58 (1991). 

Butyl rubber is an elastomeric polymer used widely in adhesives and sealants, both as primary binders and as tackifiers and modifiers. Butyl rubber is a copolymer of isobutylene with a small amount of isoprene. These materials have relatively low strength and tend to exhibit creep under load. They are useful in packaging apphcations where their low permeability to gases, vapors, and moisture can be exploited. Butyl rubber is also used as an adhesive sealant. It is generally applied from a solvent-based solution. Table 5.1 summarizes some of the important properties of butyl rubber adhesives. 

Ionomers are used in apphcations such as golf ball covers and bowling pin coatings, where their good abrasion resistance is important. The puncture resistance of films allows these materials to be widely used in packaging apphcations. One of the early applications was the packaging of fishhooks. They are often used in composite products as an outer heat-seal layer. Their ability to bond to aluminum foil is also utilized in packaging applications. Ionomers also find apphcation in footwear for shoe heels. ... 

Styrene-butadiene copolymers are used in toys, housewares, and medical applications.Thermoformed products include disposable food packaging such as cups, bowls, clam shells, deli containers, and lids. Bhster packs and other display packaging also use styrene-butadiene copolymers. Other packaging apphcations include shrink wrap and vegetable wrap. ... 

This material has excellent barrier properties and is frequently used in food packaging apphcations. Films made from PVDC have good chng properties, which is an advantage... 

Sorrentino, A., Gorrasi, G., Vittoria, V. Potential perspectives of bio-nanocomposites forfood packaging apphcations. Trends Food Sci. Technol. 18, 84—95 (2007)... 

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