Plastics

Plastics is invented by Alexander Parkes in 1856. Plastics are synthetic polymers which can be easily moulded or set into a desired shape. They rank among the most practical materials ever made. Plastic goods are used in our homes, workplaces, and educational institutions. Plastics that are as soft as cotton or as rigid as steel have been created by engineers. Engineers can create plastics that are any colour of the rainbow or as clear and colourless as crystal. Plastics can be hard or rubbery, and they can be molded into a vast array of items, such as soft fabrics, squeezable bottles, and vehicle fenders. Products made of plastic, particularly those utilized by industries, may last for many years. Plastics consist of long chains of molecules called polymers. Small molecules in repeating patterns make up these chains. A 'link' is created in the chain of the polymer by each of the smaller molecules. The chains in certain plastics are rigid and arranged like logs in a river. In others, they resemble spaghetti on a plate, tangled and stretchy. The most remarkable feature of plastics is their shapeability, which is a result of many architectures. The Greek word plastikos, which meaning "able to be shaped," is actually where the word "plastics" originates. The word 'plastic' was originally used in a patent for a mold in 1862. The first artificial plastic created is Bakelite. Bakelite is invented by Leo Hendrik Baekeland in 1907. It is made from phenol and formaldehyde. Microns are the unit used to express the thickness of plastics. 1 micron is equal to 0.000001 m.

Chloroform is a liquid that dissolves plastic. Burning plastic releases a variety of toxic gases into the atmosphere, that includes carbon monoxide, dioxins, furans and polychlorinated biphenyls. Dioxins can become a reason for cancer. Disposal of Dioxin is difficult, because it does not readily degrade in soil or water. Melamine formaldehyde Resins, noryl, carbon fibre reinforced plastic, acrylate etc. are examples of commonly used plastics. Melamine Formaldehyde Resins are used for making unbreakable plastic containers. Noryl is a plastic with the properties of metal. Carbon fibre reinforced plastic is a plastic used to make aircraft, nuclear reactors and sports equipment. Acrylate is a plastic used to make artificial teeth and lenses.

Types of Plastics

Thermoplastics and Thermosetting plastics are the two types of Plastics. They are explained as follows.

1. Thermoplastics

Thermoplastics are plastics that soften when heated and harden when cooled. Polythene, Nylon, Poly Vinyl Chloride (PVC), polypropylene, polystyrene, acrylic, teflon etc. are examples for Thermoplastics. 

i. Polythene

Polythene, also known as polyethylene or polyethene, is the most commonly used plastic material derived from ethylene monomers. It is a versatile polymer, mainly used for making packets, bags, tubes, electrical insulation and containers including jars, bottles, cups etc. About a third of all synthetic products are polyethylenes. There are three main types of polyethylene: high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (LLDPE). HDPE is the toughest and most rigid type. It is used to make bottles and jugs. LDPE and LLDPE are relatively soft and flexible. Manufacturers produce them as thin films. LDPE is used to make bread bags and LLDPE is used to make Garbage bags.

ii. Nylon

Nylon is a fibre entirely made from chemicals. It is stronger than silk. Nylon is resistant to grease and dirt. It was used in a multitude of applications, ranging from parachutes to stockings. 

iii. Poly Vinyl Chloride (PVC)

Poly Vinyl Chloride (PVC) is a thermoplastic, much stronger than polyethylene. It is used for the manufacture of electrical insulators, water proof cloth, plumbing, shoes, hand bags, raincoats, boats, bottles, furnitures etc. Poly Vinyl Chloride (PVC) is the polymer of Vinyl Chloride. Dioxin is a toxic gas that results from burning PVC.

iv. Teflon

Teflon is a polymer named Polytetrafluoroethylene (PTFE). Non stick kitchenware are coated with teflon and potassium hydrogen tartarate. It is anti-corrosive.

2. Thermosetting Plastics 

Thermosetting Plastics are plastics that remain soft when heated and permanently harden when cooled. Once hardened, thermosetting plastics cannot be reshaped by heating. Polyester, Bakelite, Epoxy, Phenolic, Melamine, Polyurethane etc. are examples for Thermosetting plastics.

i. Polyester

Polyesters are strong, tough polymer that are made in a variety of colours, shapes and sizes. They are made from chemical substances found mainly in petroleum. Polyesters are manufactured in three basic forms - fibres, films and plastics. Polyester fibres are widely used in carpets, clothing and upholstery. Polyester films are made into magnetic tapes for use in computers and tape recorders. Others serves as insulation for electrical wires or as containers. Thin polyester films provide airtight seals on containers and packages.

ii. Bakelite

About 50 years after the introduction of celluloid, the Beligian born chemist Leo Baekeland discovered in 1909 a new substance while experimenting with formaldehyde. Upon heating it become soft, after which it could be moulded and then hardened; it could also be made in powdered form, set under pressure, and heated to form a hard solid material. Nonconductive and resistant to heat and corrosion. It was named Bakelite, the first synthetic plastic. Many products were made from it, so it can be said to have triggered the start of the plastics industry. It is used to make electrical insulators and building materials. 

iii. Melamine

Melamine is a fire-resistant plastic. Firefighters' uniforms are made from melamine plastic.

iv. Polyurethane

Polyurethane foam is used for thermal insulation, sound proofing and padding. Polyurethanes are polymers in which formation of a urethane group is an important part of the polymerization process.