Polyethylene is a thermoplastic polymer made of long chains of hydrocarbons. It is the most common plastic on Earth and it has innumerable applications, including in packaging, clothing, and formulating with other polymers for synthetic rubber.
This post will tell you all about this versatile material: its physical properties, how it’s made, who uses it (and why), as well as how to recycle it using simple techniques! Warning: There are going to be a lot of acronyms. First, let’s take a look at the history of polyethylene and where it came from.
The History of Polyethylene
Polyethylene was discovered by accident in 1933 when two researchers, American Edgar C. Bain and Russian-American Isaac B. Colten was working on other projects! Bain was studying the diffusion of hydrogen into nickel carbonyl, and Colten was working on compound condensation reactions with ethylene gas. They didn’t know that they would both discover polyethylene this way! The researchers noticed under the microscope that the nickel carbonyl reacted to form a white powdery substance that looked like a solid material.
What is Polyethylene?
Polyethylene is a type of plastic with a characteristic blue hue. It’s the most common type of plastic, with over 100 billion kilograms produced every year. Polyethylene can be found in many household items, from toys and packaging to medical equipment. What polyethylene isn't used for may be discarded as landfill or recycled for use in such products as carpeting and fleece jackets.
Polyethylene is cheap to produce due to its high degree of polymerization - the number of repeating units found in one molecule. The more units there are, the cheaper it is to produce because they can be made using lower-quality materials than they would require if they had fewer units. Because of its high polymerization, polyethylene is also very resistant to stress. This resistance to stress makes Polyethylene a very effective type of plastic for making packaging materials such as food and drink bottles.
What is Polypropylene?
Polypropylene is the generic name for a family of plastics with the general formula CH2=CH-CH2-n, where n is an integer. The most common form of this polymer is polypropylene, which has the formula CH2=CH-CH2-. Polypropylene has a crystalline structure in which the chains are covalently bonded together by single bonds between carbon atoms. In this form, the chains are also much more rigid and brittle than those in polyethylene. The addition of a small number of ethylene groups to the propylene yields a new polymer, polyethylene-propylene (PEP), which has the same general formula as but with only one CH2=CH group.
Polypropylene is made by bringing a propane-based synthesis gas to high temperatures and pressures in the presence of catalysts such as iron oxide or manganese dioxide. This reaction induces side reactions to produce propylene, buto butadiene, and other branched structures. The 'poly' in polypropylene refers to how many repeated carbon atoms there are in each chain. The more repeat structures there are, the higher the molecular weight.
Polypropylene is used in the automotive, electrical, and food processing industries. The polymers can be mixed with additives to create a material that has flexibility and durability while maintaining low-friction properties. It is also used in making plastic bags and containers for consumer goods such as food, clothing, and soap.
Plastics are considered one of the most successful outcomes of polymer chemistry, despite being first created over 100 years ago. However, many mainstream applications for these materials exist due to their ability to take on any shape and hold it; creating bottles that keep beverages cold or packaging that keeps food fresh for longer than previous forms ever could.
