Question

Which of the following is not a rubber?
A. Plasticized PVC
B. Neoprene
C. Polyisoprene
D. NBR
E. Dacron
Choose the correct answer from the options given below:

• A. A and B Only
• B. C and D Only
• C. B and E Only
• D. A and E Only

Hint:

Don't confuse flexibility with elasticity! Plasticized PVC is flexible (you can bend it), but it lacks the rapid recovery and high elongation properties of true elastomers like NBR or Neoprene.

Answer 1

The Correct Option is D

Concept: Rubbers (elastomers) are polymers characterized by high elasticity and the ability to return to their original shape after being stretched. They typically have low cross-link density. In contrast, fibers and modified thermoplastics may show some flexibility but do not belong to the elastomer family.

Step 1: Identify the elastomers (rubbers).

• B. Neoprene: A synthetic rubber produced by the polymerization of chloroprene.
• C. Polyisoprene: The primary chemical constituent of natural rubber.
• D. NBR (Nitrile Butadiene Rubber): A synthetic rubber copolymer of acrylonitrile and butadiene, known for its oil resistance.

Step 2: Identify non-rubber materials.

• A. Plasticized PVC: While adding plasticizers makes Polyvinyl Chloride flexible, it remains a modified thermoplastic, not a true elastomer.
• E. Dacron: This is a brand name for polyethylene terephthalate (PET), which is a polyester fiber or thermoplastic resin, not a rubber.

Step 3: Conclusion.
Since A and E are not rubbers, Option (4) is the correct choice.