What Are The Types Of Polymerization?
The phrase "the future is now" certainly aptly describes the rapid scientific progress currently being experienced by humanity. This continuing renaissance is represented in many disciplines, including the plastics field.
Also known as polymers, these wonder substances have changed the way that most people conduct their daily lives. That said, many individuals may have only a cursory knowledge about how these materials are formed. This article will shed some light on the subject for such readers, and will provide individuals with deeper insights into the characteristics of various kinds of polymerization.
Just What are Polymers?
As was mentioned earlier, a number of readers may need a quick refresher on polymer science. Because of this, it will be useful to briefly consider what a polymer is.
A polymer is a class of molecule that is made up of a variable number of what are known as monomers. Monomers are special molecules that are usually small in size, and frequently organic in nature. Monomers have the ability to form chemical bonds with two or more related molecules. When a large enough number of monomers have joined forces, the resulting substance is known as a polymer.
While many synthetic polymers are of the plastic kind and are thus often associated with oil, there are actually many kinds of polymers that occur naturally, and these are known as biopolymers. An example would be the ubiquitous protein molecule, which is made up of large chains of monomers called amino acids.
What are the Main Kinds of Polymerization Reactions?
Monomers come into being during specialized chemical interactions that are known as polymerization reactions. These reactions come in two main varieties, including chain-reaction polymerization and step-reaction polymerization. Chain-reaction polymerization is also known as Addition, while step-reactions are often called Condensation.
Chain-reaction polymerizations are three way operations that involve two structures, including the aforementioned monomers as well as free radical catalysts. Free radicals are molecular fragments that feature free, unstable electrons. Because of this instability, free radicals usually readily interact with a wide variety substances. There are three basic steps during which free radicals and monomers combine to form polymers, including initiation, propagation, and termination.
Initiation is a the first part of the process, and begins when the first free radical interacts with a double bond monomer. Once the double bond has been broken, the free electron that started the reaction is transferred to the next available monomer atom, continuing the process.
During progression, this domino-like effect is repeated on any additional monomer atoms. It is during this time period that the formation of the polymer begins in earnest.
The termination phase is self-explanatory, and basically involves the capping of the end of the chain by a left over free radical. Once this part is done, a fully formed polymer chain will be ready for action.
Step-reaction polymerization is another popular polymer production method. Step-reactions require the presence of at least two different kinds of monomers that interact with each other under the right conditions. During the progression of step-reaction polymerizations, byproducts are formed as a consequence of the chemical processes.
What are the Basic Types of Plastic Polymers?
The two elementary kinds of plastic polymers are known as thermoplastics and thermosets. Thermoplastics are polymers that usually contain some carbon compounds. They can be formed by both condensation or addition reactions. Thermoplastic polymer molecules tend to be linear, which allows them to easily slide and move around one another. This property gives thermoplastics the ability to be easily formed and molded when subjected to high temperatures.
Thermosets are the next major kind of polymer. Thermosets have the same kinds of linkages that thermoplastics do, but also feature special connections known as cross-links. Cross-linking provides a kind of molecular scaffolding that acts to keep thermosets hard and strong, even when they are subjected to high temperatures or pressures.
What are the Types and Features of Various Finished Plastics?
Now that a little more is known about the two basic kinds of polymers, a discussion of some specific types of polymers will be in order.
High density polyethylene (HDPE) is a rigid and usually opaque brand of polymer. Because of its properties, it is used in products that include containers for motor oil, detergent, bleach, and other such chemicals.
Low density polyethylene (LDPE) is another type of commonly used industrial polymer. Unlike its high density cousin, LDPE is relatively soft and pliable. This makes it especially valuable for applications like garbage bags.
Polyvinyl chloride (PVC) is a type of polymer that has been falling out of favor due to problems with safe disposal. In the past, PVC has been widely used in pipe fittings, pipes, and tiles.
Polyethylene terephthalate (PET) is one of the more widely used polymers. It is often enlisted in the manufacture of beverage bottles, and has a wide variety of uses when recycled.
It is easy to see that there is a lot to the subject of industrial polymers. That said, individuals who have digested the information contained in this article doubtless now know much more about these modern marvels.