Polyolefins packaging

Uses. As an antioxidant in the rubber and plastics industry as a stabilizer in polyethylene and polyolefin packaging materials for foodstuffs... 

W.R. Grace started to manufacture heat-shrinkable polyolefin packaging films. At about the same time, Goodyear and Firestone initiated an investigation of the modification of rubber compounds by EB irradiation for tire applications.1... 

Figure 4. Left - topography of microtomed cross-section through a multilayer polyolefin packaging film. Centre - raw thermal conductivity contrast image. Right - thermal conductivity image postprocessing with trained neural net program.

A major use for polystyrene is in expanded (bead) form. This material is relatively tough and is used mainly as a protective packing material, particularly for electrical equipment or as sintered and shaped boards to replace paper, cardboard, etc. in packaging containers. Like the polyolefin packaging materials, PS is often observed as a non-degradable environmental pollutant on the sea-shore due to escape of beads and pieces of broken PS foam packaging. 

B. Hu et al., Recycling-oriented characterization of polyolefin packaging waste. Waste Manage. 33(3), 574-584 (2013)... 

Over 95% of pearls used in plastics are oxide-coated micas. The major application for plastics is polyolefin packaging. Recent interest in mass coloration for automotive parts could spur the already strong growth rate of pearls. 

Cereal Products. Breakfast cereals are susceptible to moisture absorption and require good water-vapor- and fat-barrier packagiag that retains dehcate flavors. Breakfast cereals are packaged in polyolefin coextmsion films in the form of pouches or bags within paperboard carton outer sheUs. 

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. 

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. 

Food packaging (electron-beam-irradiated polyolefins)... 

The stabili2ation of polyolefins used to insulate copper conductors requires the use of a long-term antioxidant plus a copper deactivator. Both A[,Ar-bis(3,5-di-/ A-butyl-4-hydroxycinnamoyl)hydra2ine (29) and 2,2 -oxamidobisethyl(3,5-di-/ A-butyl-4-hydroxycinnamate) (30) are bifimctional. They are persistent antioxidants that have built-in metal deactivators. Oxalyl bis(ben2yhdenehydra2ide) (28) is an effective copper deactivator when part of an additive package that includes an antioxidant. 

Table 10 contains some selected permeabiUty data including diffusion and solubiUty coefficients for flavors in polymers used in food packaging. Generally, vinyUdene chloride copolymers and glassy polymers such as polyamides and EVOH are good barriers to flavor and aroma permeation whereas the polyolefins are poor barriers. Comparison to Table 5 shows that the large molecule diffusion coefficients are 1000 or more times lower than the small molecule coefficients. The solubiUty coefficients are as much as one million times higher. Equation 7 shows how to estimate the time to reach steady-state permeation t if the diffusion coefficient and thickness of a film are known. 

Compared with more common plastics used as packaging materials, the compound does have some disadvantages, such as a high water vapour permeability and limited heat resistance, losing dimensional stability at about 70°C. It is also substantially more expensive than the high-tonnage polyolefins. Last but not least its biodegradability means that it must be used in applications that will have completed their function within a few months of the manufacture of the polymer compound. 

Precoated butyl latex compounds onto fabric can be used for PSAs in foil and paper lamination. These PSAs are also used in packaging and for bonding polyolefins (require adequate formulation). 

Polybutylene It is a polyolefin used for cold and hot water piping. As a blown film it is used for food packaging. 

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