RRB Group-D Model Paper 20 with answers for online practice

Explanation:

Thermoplastic: Plastics that can be deformed easily upon heating and can be bent easily.

• Linear polymers and a combination of linear and cross-linked polymers come under thermoplastics.
• Thermoplastics have low melting points are able to be re-melted and remolded and thus the material lends itself very well to plastic welding.
• Example: PVC, nylon, polythene, etc.

Thermosetting: Plastics that cannot be softened again by heating once they are molded.

• Heavily cross-linked polymers come under the category of thermosetting plastics.
• Thermosetting plastics have high melting points and tensile strength.
• Thermosetting plastic is high in molecular weight.
• High melting points and tensile strength signifies it is not a weldable plastic.
• Example: Bakelite, melamine, etc.

Properties of Plastic:

• Strong and ductile.
• Poor conductors of heat and electricity.
• Easily molded into different shapes and sizes.
• Resist corrosion and are resistant to many chemicals.