The word “plastic” covers a lot of different items and materials, though most people are familiar with the thin but strong type of plastic that is used to produce plastic bags. After the basic chemical process is complete and thin sheets or a film of plastic material is ready, pieces can be shaped and heat-sealed to make the bag or pouch that is used for groceries, garbage and waste and other needs.
Some types of bags are made with special glues, while others are stitched together for special uses.Most people think of plastic material as being very new in human use, but the truth is some plastic items have been in use for a century. In fact, one man presented plastic items at a London exhibition while the Civil War was going on in the United States. This first “plastic” was made from cellulose that was shaped while warm then cooled to help the item maintain its form.
The history of plastic shows, however, that most people date the use of plastic items from about 1909, when a material called Bakelite was used to make various everyday items. When petroleum was more widely available later in the 20th century, additional plastic production was possible. According to most historical records and industry literature, petroleum and natural gas are the key factors in plastic production today.
Plastic bags are usually made from a petroleum-based material called ethylene. These form chains of atoms that hold together well without being thick or heavy. This is the source of the term polyethylene. The material and method are perfect for the manufacture of plastic bags. There are several varieties of the polyethylene bags, identified by thickness and density. The chemical makeup of the base materials is quite different for each type of bag produced. Scientific literature shows that molecules in the plastic material branch to different extents. The more branched types have a lower tensile strength.
Different plastic bags are made using very different processes as well. Encyclopedia entries note that a 1963 Nobel Chemistry prize was awarded to the group that developed a process called vinyl polymerization. One of the key elements of plastic bag use is the method of recycling. Used plastic bags can be incinerated. They are considered stable in landfills, though they hardly decompose at all.
Because the science of plastics has become so refined and efficient, many different uses have been found for plastic bags, pouches and other containers. Some bags have handles cut into the sheets for ease of use. Some are slightly thicker to withstand rugged use. The least rugged of plastic bags may be used in situations such as laundry/dry cleaners. After the cleaned item is home, the thin, light plastic bag is most often discarded.
In contrast, some more durable plastic bags are reused in shopping situations. These may have less-branched molecules in their base materials, giving them higher tensile strength. They may have strong handles and can be printed with bright colors and logos for special use.