Plastic is a synthetic or semi-synthetic material that can be molded easily into solid objects. Plastic is an organic polymer of high molecular mass. Plastics can be divided into either thermoplastic or thermosetting plastics. Thermoplastic is a type of a polymer which can be easily melted by providing heat in order to recycle the material. Thermosetting plastics have high thermal stability, high dimensional stability, and high thermal and electrical insulating properties. Thermosetting plastics will become softer on heating and will not be able to remold into any shape when it is molded once.
A type of polymer which be easily melted or soften down just by providing heat in order to recycle the material. The atoms of this polymer is bonded by covalent bond and also by secondary weak van der Waal interactions between polymer chains. So these bonds can be easily broken by heat. And therefore can change its molecular structure. The melted thermoplastic can be placed in a mold and then cooled to give them a desired shape. Thermoplastic can be readily recycled or remolded because whenever thermoplastics are reheated they can be reshaped into a new article. When thermoplastic cools below its glass transition temperature (Tg), weak van der Waal forces between the monomer chains will form reversibly and makes the material rigid and usable. So visually in thermoplastic, monomer chains are clumped together like a ball of tangled yarn. Benefits of thermoplastic are: it offers high strength, shrink resistant and easily bendability. Thermoplastics have aesthetically superior finishes and eco-friendly manufacturing. Thermoplastics have low melting point and low tensile strength. By the process of addition polymerization thermoplastics can be synthesized. Few examples of thermoplastics are: Teflon, polyvinyl chloride, polypropylene, polystyrene etc.
Thermosetting plastics have irreversible chemical bonds between the molecules. When thermosetting plastic is heated it forms chemical bonds or cross link together permanently. It has high strength, high thermal and dimensional stability, high rigidity, resistant to deformation under load and high thermal and electrical insulating properties. Molecules of thermosetting plastics are bonded together by three-dimensional covalent bonds. Because of the presence of these strong bonds thermosetting plastics show resistance to high temperatures and provides great thermal stability. Thermosetting plastics cannot be easily remolded, recycled or reformed upon heating but it becomes softer in the presence of heat. Thermosetting plastics can be synthesized by condensation polymerization. Thermosetting plastics have excellent aesthetic appearance. Few examples of thermosetting plastics are: phenolic resins, epoxy resins, amino resins, melamine, Bakelite. Bakelite is a very poor conductor of heat and electricity and it is used for making electrical switches.
- Thermoplastics which can be easily melted and molded into a new article while thermosetting plastics which when molded once, cannot be easily remolded by heating.
- Thermoplastics can be recycled or reformed while thermosetting plastics cannot be recycled or reformed.
- Thermoplastic can be synthesized by the process called addition polymerization while thermosetting plastics are synthesized by condensation polymerization.
- Thermoplastics have low melting point while thermosetting plastics have high melting point.
- Thermoplastics have low tensile strength while thermosetting plastics have high tensile strength.
- Thermoplastics have secondary bonds between molecular chains while thermosetting plastics have primary bonds between molecular chains and held together by strong cross links.
- Thermoplastics are subjected to disruption by heat while thermosetting plastics can withstand high temperature without losing its rigidity.