M-Tech Plastics


Basics of Plastic
History of Plastic



Uses of Plastic

How are plastics made?

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.

Why are plastics used in packaging?

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.

Why do we need different kinds of plastics?

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 on 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 yoghurt.

PS (Polystyrene) is a colourless 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.

What about CFCs?

n response to concerns about the ozone layer, polystyrene manufacturers voluntarily phased out the use of chlorofluorocarbons (CFCs) in the late 1980s.

Why are plastics used in durable goods?

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 many reasons. The automotive industry chooses plastic for its durability, corrosion resistance, ease of coloring and finishing, resiliency, energy efficiency and lightweight. Lightweight, for instance, translates into lowered handling and transportation costs all down the line. Major appliance manufacturers use plastics because of their ease of fabrication and outstanding thermal insulation -- characteristics that significantly reduce energy consumption. 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 saving in production costs.

Energy Efficiency

Can plastics actually help save energy?

Yes. During their life cycle, plastic bags require about one-third less energy to make than paper bags. Foam polystyrene containers take 30 percent less total energy to make than paperboard containers. Fifty-three billion kilowatt hours of electricity are saved annually by improvements in major appliance energy efficiency made possible by plastic applications. Without the benefits provided by plastics insulation, these appliances would use up to 30 percent more energy.

What would happen to energy consumption if plastic packaging were replaced with alternatives?

Without plastics, the energy used to produce packaging would double. A 1992 study found that by using plastic packaging rather than alternatives such as glass, paper or metal, American manufacturers saved 336 trillion Btu. This is a difference equivalent to 58 million barrels of oil, 325 billion cubic feet of natural gas or 32 billion pounds of coal. 

Can some plastics be used more than once before disposal?

One of plastic's most unique properties is its durability. This durability makes it one of the materials of choice for commonly reused items such as food storage containers and refillable sports bottles. Reuse of plastics also helps offset trash disposal costs and reduces the amount of waste sent to landfills. More than 1,400 quality products made with or packaged in post-consumer recycled plastics are now commercially available, including single-use cameras, park benches, sweaters, jeans, videocassettes, detergent bottles and children's toys.

Recovery

What is recovery?

Recovery is the process of obtaining materials or energy resources from solid waste. Recovered plastics might be recycled into new products or used in process engineered fuels, where collected plastics are processed with paper into fuel pellets and then used in conjunction with coal and other fuels in industrial boilers and utility plants.

How does plastics recycling work?

Successful recovery of plastics -- like any material -- requires an infrastructure that can get plastics from the consumer and back into use as new products. The plastics recycling infrastructure has four parts:

Collection- Rather than being thrown away, plastics (primarily PET and HDPE) are collected for recycling. Curbside collection with other materials and drop-off at recycling centers are common plastics collection methods.

Handling- Plastics from collection programs are sorted to increase their value and compacted to reduce shipping costs.

Reclamation- In conventional recycling, sorted plastics are chopped, washed and converted into flakes or pellets that are then processed into new products. Advanced recycling technologies can take mixed plastics back to their original building blocks (monomers or petroleum feedstocks). These can then be recycled into a number of different products, including new plastics.

End-use- Reclaimed plastic pellets or flakes or petroleum feedstocks are used to manufacture new products.

Why is sorting so important in plastics recycling?

There are different types of plastics, just as there are different types of metal, paper and glass. Steel and aluminum have to be separated before recycling, different colours of glass must be sorted and white office paper must be separated from newspapers and paperboard boxes. Each of the six common packaging plastics has performance characteristics that make it best suited for specific applications. Purchasers of recycled resins want to be sure that these properties are retained, so handlers sort plastics by resin type to command the highest market value.

What can I recycle?

A: Since all community-recycling programs are basically independent of one another, what you can recycle depends on where you live. To find out what plastics recycling opportunities are available in your area, check with your county or town department of public works. The most common plastic resins collected are LDPE, PET and HDPE, often used in plastic bags, soft drink bottles and milk, juice and water containers respectively. Not all types of plastics are generally recycled, and recycling facilities may not be available in some areas.

What kinds of products are made with recycled plastics?

The variety of products made with recycled plastics is growing. Here are just a few examples:

  • Recycled PET can be used in producing deli and bakery trays, carpets, clothing and textiles.
  • Recycled HDPE can become bottles for laundry products, recycling bins, agricultural pipe, bags, motor oil bottles, decking and marine pilings.
  • Recycled LDPE can be used to manufacture bags, shrink film and compost bins.
  • Recycled PP can be used in automobile parts, carpets, battery casings, textiles, industrial fibers and films used for packaging products such as candy.

Can plastic be recycled back into food contact applications?

Today, some recycled plastics are used in food and beverage containers. Technical and economic barriers currently limit widespread use of recycled plastic packaging in direct contact with food.

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