Oxygen Packaging

Other characteristics Oxygen Packaging Paste [Pasty]... 

Molybdenum Oxide. Molybdenum compounds incorporated into flexible PVC not only increase flame resistance, but also decrease smoke evolution. In Table 10 the effect of molybdenum oxide on the oxygen index of a flexible PVC containing 50 parts of a plasticizer is compared with antimony oxide. Antimony oxide is the superior synergist for flame retardancy but has Httle or no effect on smoke evolution. However, combinations of molybdenum oxide and antimony oxide may be used to reduce the total inorganic flame-retardant additive package, and obtain improved flame resistance and reduced smoke. 

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. 

Polyacrylonitrile (PAN) films have outstanding oxygen and CO2 barrier properties, but only modest water-vapor barrier properties. They are for processed-meat and fresh pasta packaging laminations where an oxygen barrier is required for vacuum or gas flush packaging. 

Numerous variations and other appHcations are common for flexible packaging materials, eg, oxygen-permeable wraps for fresh red meat and produce shrinkable, low oxygen permeabiHty bags for meat and rigid tray closures. 

Incorporating EVOH as high oxygen barrier with polypropylene is used for packaging tomato catsup, barbecue sauce, mayoimaise, pickle reUsh, and other foods. Bottles fabricated from internal and external layers of polypropylene contain EVOH as the principal high oxygen-barrier material. 

Concern for personnel exposure to hydrazine has led to several innovations in packaging to minimize direct contact with hydrazine, eg, Olin s E-Z dmm systems. Carbohydrazide was introduced into this market for the same reason it is a soHd derivative of hydrazine, considered safer to handle because of its low vapor pressure. It hydrolyzes to release free hydrazine at elevated temperatures in the boiler. It is, however, fairly expensive and contributes to dissolved soHds (carbonates) in the water (193). In field tests, catalyzed hydrazine outperformed both hydrazine and carbohydrazide when the feedwater oxygen and iron levels were critical (194). A pubUshed comparison is available (195) of these and other proposed oxygen scavengers, eg, diethyUiydroxylarnine, ydroquinone, methyethylketoxime, and isoascorbic acid. 

In the area of gas permeabiUty, the low crystallinity of a typical ionomer ( 30%) results in relatively high permeabiUty to oxygen. For packaging of fresh meat this is advantageous, but in other packaging areas, combination with a barrier layer may be requited (see Barrier polymers). 

P ck g ing. Dry milk is packaged ia large bulk or small retail containers. A suitable container keeps out moisture, light, and air (oxygen). For dry whole milk, oxygen is removed by vacuum, and an iaert gas, such as nitrogen, is iaserted ia the heat space. An oxygen level of <2.0% is required by U.S. standard for premium quahty. 

The purity of oxygen from chlorate candles before and after gas filtration is indicated in Table 2. A particulate filter is always used. Filter chemicals are HopcaUte, which oxidizes CO to CO2 molecular sieves (qv), which remove chlorine compounds and basic materials, eg, soda lime, which removes CO2 and chlorine compounds. Other than H2O and N2, impurity levels of <1 ppm can be attained. Moisture can be reduced by using a desiccant (see Desiccants). Gas purity is a function of candle packaging as well as composition. A hotter burning unit, eg, one in which steel wool is the binder, generates more impurities. 

In petroleum and oxygenate finish removers, the major ingredient is normally acetone, methyl ethyl ketone [78-93-3], or toluene. Cosolvents include methanol, / -butanol [71-36-3], j -butyl alcohol [78-92-2], or xylene [1330-20-7]. Sodium hydroxide or amines are used to activate the remover. Paraffin wax is used as an evaporation retarder though its effectiveness is limited because it is highly soluble in the petroleum solvents. CeUulose thickeners are sometimes added to liquid formulas to assist in pulling the paraffin wax from the liquid to form a vapor barrier or to make a thick formula. Corrosion inhibitors are added to stabili2e tbe formula for packaging (qv). 

Increasingly, plastics are being used as parenteral packaging (qv) materials. Plastics such as poly(vinyl chloride), polyethylene, and polypropylene are employed. However, plastics may contain various additives that could leach into the product, such as plasticizers (qv) and antioxidants. PermeabiUty of plastics to oxygen, carbon dioxide, and water vapor must be tested in the selection of plastic containers. Furthermore, the plastic should withstand sterilization. Flaking of plastic particles should not occur and clarity necessary for inspection should be present. 

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