Properties of a Plastic Bag
Plastic bags are everywhere. While there has been a resurgence of companies providing reusable bags for their customers, plastic bags are still used for almost everything. The properties of plastic bags are such that the production and distribution of these bags can be harmful for the environment and people living in it.
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Function
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Plastic bags have been in use for many years as an easy and cheap holding container for food and other items. Plastic shopping bags are one of the most common forms of plastic bags. These bags were created as a tree-saving material designed to eliminate paper waste and needless tree destruction. However, the plastic bags did not have the effect that they were designed for. Plastic bags are also bad for the environment because of their chemical properties.
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Properties
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Almost all plastic bags are created from a form of petroleum melted and formed into a type of polymer thermoplastic known as polyethylene. Polyethylene is easily molded to any shape and holds together when stretched thin. It is waterproof; nontoxic to items inside the bags, break-resistant and is resistant to bacteria and other microbial growth. The plastic is mixed with other chemicals to produce a variety of strengths and textures.
Types
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There are several types of polyethylene used to make plastic bags. Low density polyethylene is used to make bread bags and bubble wrap. Linear low density polyethylene is used to make newspaper bags and dry cleaning film. Medium density polyethylene is used to make toilet paper packaging and paper towel plastic packaging. High density polyethylene is used to make grocery bags, shopping bags and air cushion bags used for packaging. Each of these bags have slightly different chemical properties.
Manufacturing
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The ways plastic bags are created can affect their final properties. Extrusion is when plastic pebbles are poured into a cylinder that heats and forms the plastic by rotation. Thermoforming is when plastic sheets are heated and blown into the desired shape. Film blowing is when a plastic fountain is shot into the air and then blown with air until it forms the desired shape. These are the most common manufacturing processes used to make plastic bags.
Recycling
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The properties of plastic bags are such that recycling can sometimes be difficult. Plastic bags create 3,097 tons of CO2 for every 100 million bags created. According to a study conducted by Chapman & Hall in 1995, plastic takes 29 units of energy to create and produces the environmental hazards of SO2, NOx, BOD, CO and CHx into the air. Recycling these bags release the same chemicals into the air again.
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References
Resources
- Photo Credit "silence is so accurate" is Copyrighted by Flickr user: tick followed tock (Mike Rolph) under the Creative Commons Attribution license.
