Did you use a plastic bag today? If you went to a store or restaurant, then it’s highly likely that you did. Such bags are made of polyethylene, and are technically a petroleum product. Each year, manufacturers worldwide produce 3-4 trillion plastic bags. In fact, Americans alone use more than 380 billion plastic bags annually.
History
Plastic bags were born in the middle 1950s. It all started with the birth of the sandwich bag in 1957. By 1969, people had begun using plastic bags for packaging food such as fruits and vegetables; and for garbage collection. After about half a decade later, retail stores began using plastic shopping bags. And by 1977, grocery stores had begun using plastic bags at their checkout lanes. Within time, department stores such as J.C. Penny also started using plastic bags over other types.
The next major development in the history of plastic bags happened in the 1990s. By 1992, supermarkets nationwide had begun recycling plastic bags as a service to their customers. The popularity of recycling plastic bags steadily increased during the 1990s. In part, this was due to the fact that by 1996, over 80% of all plastic bags that the public used were plastic.
Materials
The resins that manufacturers use to produce plastic bags are one of the keys to their features. Some of the most important features are the bags’ weight, thickness, durability, portability, cost, and recyclability.
Most plastic bags consist of polyethylene. While this material is generally resistant to various chemicals, it can become damaged when it’s exposed to various solvents, or high temperatures. The melting point for high quality polyethylene typically falls within the range of 200-250 degrees Fahrenheit.
Plastic bags are available in a wide array of grades, based on the density of their polyethylene. This can range from low-density polyethylene (LDPE), to high-density polyethylene (HDLE). Some of the most common materials contained in plastic bags include:
Ethylene Vinyl Acetate: This is a polymer that contains many properties that make it ideal for plastic bag production. When producing plastic bags, Ethylene Vinyl Acetate is often combined with other materials to produce a bag that is more durable and resistant to extreme temperatures.
Polypropylene: This is a thermoplastic polymer that produces a clear plastic. Manufacturers also use polypropylene for products such as clothing lining and (lightweight) ropes.
Polyvinyl Chloride (PVC): This thermoplastic material can be used to produce products such as plastic bags, wires, flooring and pipes.
Manufacturing
Polyethylene is the most common material that manufacturers use when manufacturing plastic bags. Manufacturers produce this versatile thermoplastic (plastic that becomes soft after being heated) in bulk.
Extrusion is one of the most common processes that manufacturers use when producing plastic bags. The first step is to place the raw plastic material (which are I actually tiny pellets) into a container that sits atop a hollow steel cylinder that’s referred to as a “barrel.” Next, a type of screw begins turning inside the barrel. This rotation pushes the plastic pellets forward, and then into the barrel.
Heat from the barrel then begins to melt the plastic pellets. Afterwards, the turning screw functions as a pump as it forces the melted plastic into a steel die. After the melted plastic leaves the die, it’s shaped into the finished product-a plastic bag. Finally, the plastic bag goes through a cooling machine that typically involves water or air. After the plastic bag is cooled, it then goes through the final stages before being shipped to various companies.
Recycling
Recycling plastic bags is one of the most practical ways to use them more efficiently. Amazingly, companies only recycle about 1% of the trillions of plastic bags that companies manufacture annually. Recycling them is one of the most practical ways to reduce the impact of plastic bags on the environment. The good news is that increasingly more establishments that use plastic bags (such as grocery stores) accept them for recycling. Many local recycling programs also accept plastic bags as part of their program, which makes recycling them more feasible for those people interested in the option.