Barrier plastic packaging

Althou PVDC resins have been around since the 1930 s, a period of 50 years, it has been Just since the availability of EWCH resins over the past ten years that hi barrier plastics packaging has grown so rapidly. 

Bob A. Howell, PhD, is a Professor in the Department of Chemistry at Central Michigan University in Mount Pleasant, Michigan. He received his PhD in physical organic chemistry from Ohio University in 1971. His research interests include flame-retardants for polymeric materials, new polymeric fuel-cell membranes, polymerization techniques, thermal methods of analysis, polymer-supported organoplatinum antitumor agents, barrier plastic packaging, bioplastics, and polymers from renewable sources. 

Keywords Barrier plastic packaging, radical dehyrohalogenation, poly(ene) formation, high-surface-area carbon, defect structures, metal-promoted dehydrochlorination, copolymer... 

Sugared cereals are often packaged in aluminum foil or barrier plastic, eg, ethylene vinyl alcohol, laminations to retard water vapor and flavor transmission (see Wheat and other cereal grains). 

Packaging (paper and plastic) packaging adhesives release coatings barrier coatings Photochemical machining (89) micromechanical parts optical waveguides... 

With the growth of plastic use in containers and packages, requirements to make them more compatible or useful resulted in new developments occuring and continue to occur. The two major approaches for providing permeability resistance in plastic containers involve chemically modifying the plastics surfaces and, more important from a marketing standpoint, the use of barrier plastics with nonbarrier types to meet cost-to-performance requirements. This is achieved through coextrusion, coinjection, corotation, and other such processes (Chapter 8). 

Packaging trends involve lower cost, more functionality, volume growth, shorter product life-cycles and increased value. Rigid plastic packaging now dominates markets which were previously the exclusive realms of materials such as glass and metal, despite the fact that some technical aspects of plastic are still inferior to those of such traditional materials, e.g. the failure of plastics to withstand high temperatures without deforming, or barrier properties of a standard comparable to that... 

Salame M Plastic Film Technology High Barrier Plastic Films for Packaging. Tech-nomic, Lancaster, Basel... 

Another important packaging development area is plastic. Various plastics have been and continue to be used high- and low-density polyethylene (HDPE, LDPE), polyvinyl chloride (PVC), polystyrene (PS) and various barrier plastics. These can be formed into bottles of conventional shape or fed into machines producing form-fill-seal packages, typically cups. 

Plastic Packaging Materials for Food Barrier Function, Mass Transport, Quality Assurance and Legislation. O. Piringer and A. L. Baner (eds), Wiley-VCH, Weinheim, FRG, 2000. 

Baner, A. L. (2000). Case study Styrene monomer migration into dairy products in single serve portion packs. In "Plastic Packaging Materials for Food Barrier Function, Mass Transport, Quality Assurance, and Legislation" (O.-G. Piringer, and A. L. Baner, eds.), pp. 427-443. Weinheim (Feberal Republic of Germany), Wiley-VCH. 

Of the styrene copolymers used for food packaging the styrene-acrylonitrile copolymer known as SAN still needs to be mentioned. SAN copolymers possess better mechanical properties and better resistance to oils and aroma compounds than PS. Copolymers with acrylonitrile fractions of 20-35 % find uses as household and camping dishes. Copolymers with a higher acrylonitrile content (> 60%) have earned particular importance as barrier plastics. With an increasing acrylonitrile fraction, the gas permeability decreases sharply. 

Barrier Plastics. When plastics replace metals and glass in packaging, their permeability is often a limiting property. Barrier performance generally increases with density and crystallinity. The most promising barrier plastics include ethylene/vinyl alcohol, polyvinylidene chloride, polyacrylonitrile, and polyethylene naphthoate. These are used most efficiently by laminating them to commodity plastics such as polyethylene and polyethylene terephthalate. 

Different barrier plastics meet different requirements. A very popular barrier plastic is EVOH (ethylene-vinyl alcohol copolymer) that can be tailored to the needs of packages and other products.80 Generally the thickness ranges from 0.5 to 3.0% of the wall thickness it can be thicker if higher barrier is required. Generally EVOH thickness greater than 8% of the container sidewall can lead to internal structural failures that can fail on drop tests. Also a very thick layer tends to be difficult to process consistently. The EVOH s crack resistance improves as its ethylene content increases. 

Aluminum is an impermeable UV-VIS photon barrier. Therefore, packaging of this metal, metal tubes, foil or coated on plastic films can provide 100% light protection for the drug preparations stored inside. 

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