The Capacity of Plastic Bags

Literature Review for Statistics Project

Our project was chosen with practicality and accessibility in mind – people shop and use plastic grocery bags to carry things in every day. We were surprised to find that despite the widespread use of plastic bags, there has been little to no research done to determine the weight capacity of plastic bags and whether or not double bagging holds significantly more weight. Although the latter question may seem to be common knowledge, we expected to find a considerable amount of experimentation done on the weight capacity of plastic bags in general. The only research we could find on the topic was an amateur research experiment similar to ours. We also found information on the production process and chemical makeup of plastic bags and how that could relate to their weight capacity.

A group user of the website Gomestic ran an experiment similar to ours. They tested the weight capacities of plastic bags, but tested bags from different stores against each other. They also only used 4 bags from 4 stores, totaling only 16 trials. They used different items with predetermined weights to measure the weight capacity of the plastic bags, but did not appear to have a consistent procedure in introducing the weights. The experiment was run in a gym with the bag hanging over a bar, and results were recorded in a series of bar graphs. Overall, they found that 14 out of the 16 bags they experimented on held at least 20 kg, or 44 lbs. (Lunch Club, 2007). The researchers also concluded that the purpose the bags were being used for – ie groceries, clothes, etc – also had an impact on how strong the plastic bag was.

The way in which plastic bags are produced can impact their weight capacity. Certain kinds of plastic are made for different purposes, and thus are produced differently and made of different materials (Lajeunesse, 2004). As another article states, “the material used to produce plastic bags has several characteristics which makes it desirable as a packaging source” (Meher,2011) In the manufacturing process, petroleum, natural gas, and additives are heated together and then cooled, making the end result durable and resistant (Meher, 2011).The kind of polyethylene (and the branching of these) used has a considerable impact on the quality and characteristics of the plastic. “Branching can influence a number of physical properties including tensile strength and crystallinity” (Lejeunesse, 2004). This tells us that the chemical makeup of the bag has a great deal to do with how strong it is, and thus how much weight it can hold without breaking. The production process and chemical makeup of plastic bags are what make plastic bags so effective and give them their ability to hold comparatively large amounts of weight.