Use of phthalic anhydride in polymer/chemical industry: which statement best matches a major application?

Introduction / Context:
Phthalic anhydride (PA) is an important aromatic anhydride used to make phthalate plasticisers and alkyd resins, among other products. Recognising its core role helps avoid misattribution to unrelated polymers.

Given Data / Assumptions:

• PA + alcohols → phthalates (e.g., DOP/DEHP historically), widely used as plasticisers.
• PA is not a direct precursor to PVC or nylon-6.
• PA contributes to alkyd resin synthesis for coatings.

Concept / Approach:
Plasticisers are low-molecular-weight esters that impart flexibility to PVC and other polymers. PA is esterified with suitable alcohols to produce these plasticisers. PVC itself is produced from vinyl chloride, and nylon-6 from caprolactam, not from PA.

Step-by-Step Solution:
Match PA's chemistry (aromatic anhydride) with esterification to plasticisers.Eliminate routes unrelated to PA (PVC monomer, nylon-6).Select “As a precursor to plasticisers.”

Verification / Alternative check:
Coating resin (alkyd) and plasticiser sectors consume large volumes of PA.

Why Other Options Are Wrong:
PVC and nylon-6 have different precursors; insecticides are not the principal application.

Common Pitfalls:
Confusing “used in PVC” as plasticiser in PVC compounding versus “used to make PVC.”

Final Answer:
As a precursor to plasticisers