Types of Plastics: Definitions, Examples & Application

Types of plastics are broadly classified into thermoplastics and thermosetting plastics. Plastic is a polymer that can be molded when it is soft and hardened to hold a particular shape. A plastic is an organic compound with a higher molecular weight. Due to its non-reactive properties and durability, it is the most used polymer worldwide. There are different types of plastics, for example- polythene, Nylon and many more. Based on the applications, plastics can be further classified as commodity, engineering and high-performing plastics. 

The first plastic was made in the year 1869 in a New York firm by John Wesley Hyatt. Hyatt provided a substitute for the ivory being used on the billiards by treating cellulose, derived from cotton fiber, with camphor. The product obtained could be molded into a variety of shapes and was capable of imitating natural substances like tortoiseshell, horn, linen, and ivory.

Read More: Synthetic polymers

Key Terms: Plastic, Polymer, Carbon Chain, Organic Compound, Thermoplastic, Thermosetting Plastic

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What is Plastic?

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Plastic can be defined as a synthetic material made from a wide range of organic polymers such as polyethylene, PVC, nylon, etc.. The key characteristic of plastics is that it can be molded into shape while soft, and then set into a rigid or slightly elastic form. 

• Plastic is a polymer that can be colored, reused, molded as per requirements.
• It carries a long chain of carbon as its core structure.

Long Carbon Chain in Plastics

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Types of Plastic

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Plastic can be divided in two categories- 

1. Thermoplastic
2. Thermosetting Plastic

Thermoplastic

Thermoplastics are those types of plastics that can be easily molded at a certain temperature. It is also called Thermosoft Plastic. These plastics can be further divided into seven types-

Polyethylene Terephthalate

Polyethylene Terephthalate can be considered as a wrinkle-free plastic that is also known as PET. 

• PET can be characterized as an aliphatic polyester.
• It is recyclable and can be reused.
• As PET has a unique ability to prevent Oxygen to get past it, it is hugely used in the packaging and textile industry.
• It is also used in packaging carbonated drinks as it stops Carbon dioxide from getting out of the bottle.
• PET is very light-weight and semi-crystalline in its stable form.
• Chemical Formula of PET is (C₁₀H₈O₄)_n

Structure of PET

Polyvinyl Chloride

Polyvinyl Chloride is one of the most economical and versatile thermoplastic polymers world-wide that is also known as PVC or Vinyl. 

• German chemist Eugen Baumann incidentally invented PVC in 1872.
• There are two categories of PVC- Rigid PVC and Flexible PVC.
• Rigid PVC is the type of plastic mostly used in making doors, and windows. Flexible PVC is normally used in making pipes for plumbing.
• It is also used in the electrical industry.
• PVC has a melting point of 200-260 degrees celsius.

Structure of PVC

Polyethylene

Polyethylene, simply known as Polythene is the most used type of plastic. It is made by the process of polymerization of ethylene monomers. 

• It is used in industries like- clear food packaging, shopping bags, detergent bottles as well as automobile fuel tanks.
• There are four types of Polythene- Low-density polyethylene, Medium-density polyethylene, High-density polyethylene, and Ultra-high molecular weight polyethylene.
• The melting point of polythene is between 115 degrees Celsius to 135 degrees Celsius.
• Density of Polythene varies between - 0.88 grams to 0.96 grams per cubic centimeter.
• Chemical Formula of Polythene is- (C₂H₄)ₙ

Structure of Polythene

Polypropylene

Polypropylene is defined as a type of plastic or synthetic resin that can be created as the result of polymerization of propylene. Therefore, propylene can be considered as the monomer of Polypropylene. 

• It is non-polar.
• It has a melting point of 130-170 degrees celsius.
• Polypropylene is used in machinery industries as it is the key element of making plastic parts for the instruments.
• It is semi-crystalline.
• Rigidity is one of the prominent characteristics of Polypropylene.
• Chemical formula- (C₃H₆)_n

Structure of Polypropylene

Polystyrene

Polystyrene is defined as a polymer that is created from a monomer called styrene. Styrene is a liquid hydrocarbon that is made from petroleum. 

• This type of plastic is harmful for human beings and the environment.
• Polystyrene is made from three monomers- Acrylonitrile, Styrene, and Butadiene.
• The density varies between 1.06 to 1.08 grams.
• Polystyrene is hard and transparent, hence, it is used in the food-service industry.
• It is used in making containers, disposable eating utensils, and foamed cups, plates, bowls etc. 
• Chemical formula- (C₈H₈)_n

Structure of Polystyrene

Nylon

Nylon is a silk-like synthetic polymer made from polyamides that have high molecular weight.

• Nylon is known for its strong and elastic characteristics.
• Oil or other chemical particles have very little effect on Nylon.
• This type of plastic is of four types- Nylon 6, Nylon 510, Nylon 1,6 and Nylon 66.
• As it does not absorb water, it dries pretty quickly.
• It is wrinkle-proof.
• Mostly used in the fabric industry.

Structure of Nylon

Others

There are other type of plastics like polycarbonate (PC) which is also known as Lexan, Makrolon, and Makroclear. As PC is a toxic compound it is banned from use as the basic elements for making baby bottles, food can liners, ketchup containers etc. in many countries.

Thermosetting Plastic

Thermosetting Plastics are those type of plastics that can not be molded more than once. These are also known as thermosetting polymers. 

• Bakelite, Cyanate esters, Duroplast, Epoxy resin, Fiberglass, Melamine are examples of Thermosetting Plastics.
• Once heated, it becomes very rigid.
• Thermosetting Plastics are mostly used in the manufacturing of construction equipment panels, insulators, and agricultural equipment.
• Once molded it these type of plastics rarely reacts with other chemicals.

Types of Plastics

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Types of Plastic based on Application

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The plastics can be mainly divided into three categories based on their usage as well- 

Commodity Plastics

The Commodity Plastics do not show any special properties and have lower price rates. These type of plastics are mainly used in packaging industries. Polyethylene, Polypropylene, PVC etc are examples for this type of plastics.

Engineering Plastics

Due to their extraordinary thermal or mechanical properties these type of plastics are extensively used in engineering industries. Nylon is a perfect example of this category of Plastics.

High-Performance Plastics

These are the most expensive type of plastics as they are non-reactive to any chemical reactions. They are known for their strong, rigid and temperature-resistant properties. Polytetrafluoroethylene, Silicone, etc. are the most well-known examples of this category.

Read More: Thermosetting Polymers

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Things to Remember

• Plastics can be divided into two categories- Thermoplastic and Thermosetting Plastic. 
• The most important element of plastic is an organic compound with a higher molecular weight.
• Plastic is a polymer that can be colored, reused, and molded as per requirements.
• Thermoplastics are those plastics that can be easily molded at a certain temperature.
• Thermosetting Plastics are those type of plastics that can not be molded more than once.

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