Plastic resins are a crucial component of our modern society. From wastebaskets to IV lines used in hospitals, plastics make life more convenient and safe. “Plastic Resins” is a very broad term, and covers various types of plastics such as acrylics, epoxies, and nylons. The importance of plastic resins becomes obvious when one thinks of the many products and industries that plastics are used.
One way to think of the chemical nature of a plastic is to think of a long metal chain. Each of the links in the chain represents a “monomer,” or single unit molecule. When those links are combined together in a chain, it is called a “polymer.” Those chains can even be cross-linked with each other in different ways to provide strength. An example of a cross-linked polymer would be the hull of a boat or a bathtub. These cross-linked plastic resins are known as thermoset plastics. These are plastics that are not able to be melted. The reason for this is because the long polymer chains can not be untangled from one another due to the high degree of cross-linking. On the other hand, a thermoplastic is able to melt, and makes up the majority of plastics. The polymer configuration and ability to cross-link in a three dimensional structure is what gives different plastics their amazing properties.
Two examples of a common plastic resin you may be familiar with are high and low density polyethylene, (HDPE and LDPE). High density denotes a high strength to density ratio, and can be used in products such as corrosion resistant pipes. LDPE is used in many applications, with the most common being plastic bags.
The life of a plastic begins at the same source that gasoline for your vehicle is found. Hydrocarbons, which make up the single unit molecules (monomers), are derived from crude oil in a process called cracking. The cracking process yields several different products, but the fundamental principle is that the heavy crude oil is broken up into lighter oil fractions. The hydrocarbons obtained from this process are further treated chemically to produce the desired monomers for the many different types of plastics. Once the monomers are produced, the next step is to link them together into polymer chains. When linked together in chain form, the polymerized plastic is often in the form of resin pellets. These resin pellets are easily distributed and transported, and companies will purchase the pellets to create their own unique products.
With basic understanding of the preparation and chemical nature of a plastic, it is easy to see why there are so many different types of plastic resins. Many different monomers for plastics can be created, and then the monomers can be polymerized in different ways when cross-linking is implemented. These various factors lead to an extensive number of different plastic resins that can be manufactured.
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