Life Cycle of a Plastic Bag

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The Life Cycle of a Plastic Bag Material Extraction Plastic bags start their life cycle as crude oil in countries such as Saudi Arabia and the United States (thisismoney). Plastic bags have become so popular that about five trillion of them are produced each year to meet the market demand (thisismoney). As a result, about sixty million barrels, which account for 0.2% of all the yearly oil extracted from all over the world worth roughly four billion US dollars, go into making plastic bags (thisismoney, planetsave). It should be noted that planetsave.com is a pro-environment website, so some of the numbers from that source might be exaggerated. Material Processing After oil is extracted, it is heated to produce ethylene, which is then polymerized to produce polyethylene, a very dense liquid that is used to make most plastic bags (thisismoney, Burke). Polyethylene comes in two forms: high density polyethylene (HDPE), and low density polyethylene (LDPE) (Burke). HDPE combines strength, endurance and lightweight, which is why it is used to make bottles, pipes and heavy duty bags (thisismoney). HDPE is naturally transparent, and so dyes are used to give color to the plastic bags and other products (Burke). There is also a process called branching, which means replacing the polymer chain with other forms or variations of the monomer, that change the characteristics of the plastic (Burke). Polymers that are highly branched produce thinner plastic that is difficult to see through, and is easily torn (Burke). Highly branched polymers are used to make the weak, flimsy plastic bags like dry cleaning bags and plastic bags that are available in grocery stores (Burke). Food bags, such as Ziplocs, are made from not so highly branched polymers, which explains why they are stronger and more transparent than grocery bags (Hill). The final step of material processing is forcing the
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