Plastic bags, often called poly bags, are made with two same sized plastic sheets (of thickness generally less than 250 microns) that are attached on three sides, and one side is the opening of the bag.
Plastic garbage bags are made from polyethylene, which is a polymer material. Polyethylene starts as ethylene which is mined from natural gas and then treated so that it forms a polymer. Polymers have long chains of carbon-hydrogen atoms. Their molecular structure can differ, depending on the type of polyethylene being formed. All polyethylene variants can help in making plastic garbage bags.
Here are the common materials that are used in making garbage bags:
As discussed before, plastic is generally made from polymers, as these molecules are large, have a repeating pattern, and are easy to create. In garbage bags, the repeating pattern is made of ethylene. With the help of chemical processes, ethylene is converted to polyethylene, which is used for creating all garbage bags. Polyethylene has winding chains of carbon atoms that are combined with hydrogen atoms and it is in a patterned structure, which is easy to mould into various densities and shapes.
There are various sources of polyethylene, and they all are related to some type of fossil fuels. Common sources of polyethylene are natural gas and petroleum, and they are vital ingredients in all plastic bags. When they are properly refined, they produce ethylene, which is then changed to polyethylene. This is done mostly with natural gas that gives a flexible polyethylene substance that can be changed into any shape or color.
Low Density Polyethylene (LDPE)
LDPE is made of low density polymer material. These polyethylene chains spread out and create branches. As a result, the plastic they form is extremely light – almost like a film. This light plastic is used to create tear-away bags that are used by dry cleaners to wrap clothes.
High Density Polyethylene (HDPE)
HDPE is the most common polyethylene that is generally used to make heavy duty garbage bags. This plastic is made of linear molecular chains that have very little branching. Since the molecular pattern is mostly straight, it becomes a strong material and you can find tough garbage bags made of this plastic.
Linear Low Density Polyethylene (LLDPE)
These plastics are linear in nature and do not have branches. And yet, they are not as strong as HDPE polymers. However, they stretch more easily before ripping, and this is why they are used where the garbage consists of sharp objects. However, one problem with this material is that it is costlier than other options.
While garbage bags are recyclable, they cannot be returned to an organic state (although scientists are carrying research on plastic-eating bacteria). These bags can be recycled to make other bags, but are generally used to create synthetic material like composite lumber. While plastic bags are biodegradable, they are still a preferred environmental choice as their manufacturing process uses 70% less energy and 50% fewer greenhouse gas than that of paper bags.