Sunday, September 12, 2010

Facts about Plastics

Q: How are plastics made?
A: Plastics consist of building blocks called hydrocarbons, typically derived from petroleum or natural gas. These monomers (small molecules) are bonded into chains called polymers or plastic resins. Different combinations of monomers yield resins with special properties and characteristics.
Q: Why are plastics used in packaging?
A: Packaging serves many purposes, but one of its primary functions is to help protect the quality of goods - ranging from sensitive electronics to fresh and prepared foods - during shipping, handling and merchandising. Plastics are a versatile family of materials that are suitable for a wide range of packaging applications. In many cases, plastics offer the best protection while using minimal resources and creating less waste than alternative materials. In fact, 400 percent more material by weight would be needed to make packaging if there were no plastics, while the volume of packaging would more than double.
Q: Why are plastics used in durable goods?
A: Manufactured items with a useful life of more than three years - cars, appliances, computers, etc. - are called durable goods. Manufacturers of durable goods choose plastics for the following reasons:
1. The automotive industry chooses plastic for its durability, corrosion resistance, ease of coloring and finishing, resiliency, energy efficiency and light weight. Light weight, for instance, translates into lowered handling and transportation costs all down the line. Where a plastic film (as in stretch wrap) can replace a heavy shipping crate or carton, the weight savings can be an order of magnitude or more.
2. Major appliance manufacturers use plastics because of their ease of fabrication and outstanding thermal insulation characteristics, that significantly reduce energy consumption.
3. The building and construction industry uses vinyl siding for homes because of its appearance, durability, ease of installation and energy efficiency. Plastics can reduce energy consumption for the auto, appliance, and building and construction industries, providing a substantial savings in production costs.
Q: Why do we need different kinds of plastics?
A: Copper, silver and aluminum are all metals, yet each has unique properties. You wouldn't make a car out of silver or a beer can out of copper because the properties of these metals are not chemically or physically able to create the most effective final product. Likewise, while plastics are all related, each resin has attributes that make it best suited to a particular application. Plastics make this possible because as a material family they are so versatile.

Six resins account for nearly all of the plastics used in packaging:
• PET (polyethylene terephthalate) is a clear, tough polymer with exceptional gas and moisture barrier properties. PET's ability to contain carbon dioxide (carbonation) makes it ideal for use in soft drink bottles.
• HDPE (high density polyethylene) is used in milk, juice and water containers in order to take advantage of its excellent protective barrier properties. Its chemical resistance properties also make it well suited for items such as containers for household chemicals and detergents.
• Vinyl (polyvinyl chloride, or PVC) provides excellent clarity, puncture-resistance and cling. As a film, vinyl can breathe just the right amount, making it ideal for packaging fresh meats that require oxygen to ensure a bright red surface while maintaining an acceptable shelf life.
• LDPE (low density polyethylene) offers clarity and flexibility. It is used to make bottles that require flexibility. To take advantage of its strength and toughness in film form, it is used to produce grocery bags and garbage bags, shrink and stretch film, and coating for milk cartons.
• PP (polypropylene) has high tensile strength, making it ideal for use in caps and lids that have to hold tightly to threaded openings. Because of its high melting point, polypropylene can be hot-filled with products designed to cool in bottles, including ketchup and syrup. It is also used for products that need to be incubated, such as yogurt.
• PS (polystyrene), in its crystalline form, is a colorless plastic that can be clear and hard. It can also be foamed to provide exceptional insulation properties. Foamed or expanded polystyrene (EPS) is used for products such as meat trays, egg cartons and coffee cups. It is also used for packaging and protecting appliances, electronics and other sensitive products.
Q: What about CFCs (Cloro Floro Carbon)?
A: Most (nearly 70 percent) of polystyrene foam products never were made with chlorofluorocarbons (CFCs). In the late 1980s, those few polystyrene manufacturers that used them announced the voluntary phaseout of CFCs.

Courtesy: SPI

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