Types Of Plastics
Thermoplastics and thermosetting plastics are two major categories of polymers or plastics, distinguished by their response to heat and the nature of their chemical bonds. The key difference lies in how they react to heat and whether they can be melted and reshaped or not
1. Thermoplastics:
Definition:
Thermoplastics are polymers that can be melted and reshaped multiple times without undergoing any significant chemical change
Behavior when Heated:
When heated, thermoplastics soften and become pliable. This allows them to be molded or shaped into different forms.
Once cooled, they solidify and retain the new shape.
This process can be repeated several times without degrading the material
Chemical Bonds:
The polymer chains in thermoplastics are held together by relatively weak intermolecular forces, such as Van der Waals forces
Examples of Thermoplastics:
Polyethylene (PE)
Polypropylene (PP)
Polyvinyl chloride (PVC)
Polyvinyl chloride (PVC)
Polyethylene terephthalate (PET)
Polystyrene (PS)
Applications:
Packaging materials, containers, pipes, toys, and various consumer goods.
2. Thermosetting Plastics:
Definition:
Thermosetting plastics are polymers that, once molded and set, undergo a chemical reaction that makes them infusible and insoluble
Behavior when Heated:
When heated, thermosetting plastics undergo a chemical change, typically involving the formation of covalent bonds between polymer chains.
Once set or cured, they cannot be melted or reshaped without undergoing degradation
Chemical Bonds:
The polymer chains in thermosetting plastics are held together by strong covalent bonds
Examples of Thermosetting Plastics:
Epoxy
Phenolic
Melamine formaldehyde
Urea formaldehyde
Polyurethane (in some forms)
Applications:
Composites, adhesives, electrical components, and in applications where dimensional stability and resistance to heat are crucial.
Key Differences:
Reversibility:
Thermoplastics are reversible and can be melted and reshaped multiple times.
Thermosetting plastics undergo an irreversible chemical change upon curing, and once set, they cannot be melted or reshaped.
Chemical Bonds:
Thermoplastics have weaker intermolecular forces (Van der Waals forces).
Thermosetting plastics have stronger covalent bonds between polymer chains.
Applications:
Thermoplastics are suitable for applications where flexibility, recyclability, and ease of processing are important.
Thermosetting plastics are used in applications where heat resistance, dimensional stability, and hardness are critical.
Both types of plastics have their advantages and are chosen based on the specific requirements of the application. The choice between thermoplastics and thermosetting plastics depends on factors such as the intended use, processing requirements, and desired material properties.