Plasticisers: high-boiling additives impart toughness and flexibility to plastics at ordinary temperature. Which of the following is NOT typically used as a plasticiser?

Introduction / Context:
Plasticisers are relatively large, high-boiling, often polar molecules that reduce intermolecular attractions in a polymer, lowering glass-transition temperature and increasing flexibility. Identifying the typical chemical families used as plasticisers helps avoid confusion with solvents or monomers that have different volatility and compatibility profiles.

Given Data / Assumptions:

• Common plasticisers include phthalates, phosphates, adipates, sebacates, and certain stearate esters.
• Ethylene glycol (EG) is a small, low-boiling diol used as antifreeze/monomer, not as a primary plasticiser for engineering plastics.

Concept / Approach:
Effective plasticisers must be sufficiently non-volatile and compatible to remain in the polymer matrix during service. EG’s low molecular weight and high volatility make it unsuitable as a standard plasticiser; it tends to migrate/evaporate and can act as a solvent or reactant rather than a durable plasticiser. In contrast, phthalate esters, tricresyl phosphate, adipates/sebacates, and stearate esters are classic plasticiser families used in PVC and other polymers.

Step-by-Step Solution:

Verification / Alternative check:
Formulation tables for PVC list dioctyl phthalate (DOP), diisononyl phthalate (DINP), dioctyl adipate (DOA), tricresyl phosphate (TCP), and stearates; EG is absent as a durable plasticiser.

Why Other Options Are Wrong:

• Phthalate esters/TCP/adipates/sebacates/stearate esters: all widely used plasticiser classes.

Common Pitfalls:
Equating “any liquid” with “plasticiser”; permanence and compatibility are crucial.

Final Answer:
Ethylene glycol