Plasticisers and Stabilisers Questions and Answers

Answer: B

The solvents remove plasticizer and raise \(T_{g}\).

Rigid PVC has a glass transition temperature around 80 °C. Flexible PVC tubing contains a large amount of plasticizer (typically a phthalate), whose small molecules sit between the chains, add free volume and lower \(T_{g}\) below room temperature. Organic solvents dissolve and leach out this plasticizer, so \(T_{g}\) rises back towards that of unplasticized PVC and the tube turns stiff.

Plasticizing PVC would lower \(T_{g}\) and make the tube softer, not stiffer. Removing plasticizer cannot lower \(T_{g}\), and the solvent does not chemically react with PVC.

Answer: A

The correct matching is P-3; Q-4; R-2; S-1.

1. Dibutyltin maleate is an organotin heat stabilizer, which stops PVC losing HCl during processing (P-3).
2. Epoxidized soybean oil is a plasticizer (it also helps stabilize) (Q-4).
3. Chlorinated paraffin wax is a cheap secondary plasticizer, an extender used to replace part of the primary plasticizer (R-2).
4. Calcium stearate is a lubricant that eases flow and release from the metal surfaces (S-1).

The other options assign the tin compound as an extender or plasticizer, or the stearate as a heat stabilizer or plasticizer, which do not match the main functions of these additives.