Which statement correctly describes PVC compared with polythene?

Which statement correctly describes PVC compared with polythene?

• A. PVC is strong, hard, and less flexible; plasticisers can make it more flexible
• B. PVC is weaker than polythene and very flexible
• C. PVC is a gas at room temperature
• D. PVC cannot be made flexible

Answer: (A)

Understanding how plasticisers change polymers helps explain this. PVC has chlorine atoms in its chain, which makes the polymer chains attract each other strongly. Those strong intermolecular forces make unplasticised PVC hard, strong, and not very flexible. When plasticisers are added, they insert between the PVC chains and reduce these forces, allowing the chains to move past one another more easily. This increases flexibility, making PVC usable in many flexible products. Polythene is a non-polar hydrocarbon and its chains don’t attract each other as strongly, so it can be flexible, especially in the lower-density grades. Unplasticised PVC, however, is typically less flexible than many forms of polythene. So the description of PVC as strong, hard, and less flexible, with plasticisers able to make it more flexible, matches how PVC compares with polythene.

Understanding how plasticisers change polymers helps explain this. PVC has chlorine atoms in its chain, which makes the polymer chains attract each other strongly. Those strong intermolecular forces make unplasticised PVC hard, strong, and not very flexible. When plasticisers are added, they insert between the PVC chains and reduce these forces, allowing the chains to move past one another more easily. This increases flexibility, making PVC usable in many flexible products.

Polythene is a non-polar hydrocarbon and its chains don’t attract each other as strongly, so it can be flexible, especially in the lower-density grades. Unplasticised PVC, however, is typically less flexible than many forms of polythene. So the description of PVC as strong, hard, and less flexible, with plasticisers able to make it more flexible, matches how PVC compares with polythene.