Which of the following statements is true about PVC (polyvinyl chloride) and polythene?

A.They are thermoplastics

B.They are thermosetting plastics

C.They are examples of natural substances

D.They are natural fibres

 

The correct option is A. They are thermoplastics.

1. What are Thermoplastics?
   • Thermoplastics are a type of plastic that can be melted and reshaped repeatedly when heat is applied.
   • When cooled, they harden again, and this process can be repeated without changing the chemical structure of the material.
   • Thermoplastics are widely used in manufacturing because they can be molded into different shapes and reused.
2. PVC (Polyvinyl Chloride):
   • PVC is one of the most commonly used thermoplastics.
   • It is made by polymerizing vinyl chloride monomers.
   • Uses of PVC: It is used in the production of pipes, flooring, clothing, medical devices, and electrical insulation.
   • When heated, PVC becomes soft and can be molded into various shapes. Once cooled, it hardens, and the process can be repeated.
3. Polythene (Polyethylene):
   • Polythene is another example of a thermoplastic polymer.
   • It is made by polymerizing ethylene monomers.
   • Uses of Polythene: It is used in the production of plastic bags, containers, toys, bottles, and various other items.
   • Just like PVC, when polythene is heated, it softens, allowing it to be molded into different forms. On cooling, it solidifies, and the process can be repeated.
4. Why are the Other Options Incorrect?
   • B. Thermosetting Plastics:
     • Thermosetting plastics are different from thermoplastics. They are cured or hardened permanently when they are first heated and molded. After they set, they cannot be remelted or reshaped.
     • Examples of thermosetting plastics include Bakelite and Melamine, not PVC or polythene.
   • C. Natural Substances:
     • PVC and polythene are synthetic plastics, meaning they are man-made through chemical processes. They are not natural substances.
     • Natural substances like rubber and cotton are derived from plants and animals, but PVC and polythene are derived from petrochemicals.
   • D. Natural Fibres:
     • Natural fibres are derived from natural sources, like cotton, wool, and silk, which come from plants and animals.
     • PVC and polythene are synthetic, not natural fibres. They are types of plastics, not fibres.

Additional Information:

• Properties of Thermoplastics:
  • Recyclability: Since thermoplastics can be melted and reshaped, they are highly recyclable.
  • Flexibility: Thermoplastics like PVC and polythene can be made flexible or rigid, depending on the additives used during production.
  • Durability: These materials are durable, weather-resistant, and can withstand various physical stresses.
• Environmental Impact:
  • Though thermoplastics like PVC and polythene are recyclable, improper disposal can lead to environmental pollution, especially in marine environments.

Both PVC and polythene are important thermoplastics used in various industries for products that are lightweight, durable, and easy to shape. Their ability to be melted and reused makes them versatile materials in the world of plastics.