Free-radical addition polymerisation: which initiators commonly decompose to generate free radicals for chain initiation?

Introduction / Context:
Free-radical polymerisation requires radical initiators to start chain growth in monomers like styrene, acrylates, and vinyl chloride (in appropriate systems). Identifying initiator classes is fundamental in polymer reaction engineering.

Given Data / Assumptions:

• Initiators decompose thermally or under redox to form radicals.
• We compare typical initiators vs strong acids.

Concept / Approach:
Organic peroxides (e.g., benzoyl peroxide, dicumyl peroxide) and azo compounds (e.g., AIBN) are classic radical sources. Strong mineral acids such as sulphuric and hydrofluoric acid are not radical initiators for addition polymerisation; they catalyse ionic mechanisms (e.g., cationic) in other contexts, but not as radical sources by decomposition.

Step-by-Step Solution:
Recall initiator families for radical polymerisation.Identify peroxides as thermal radical generators.Eliminate acids as non-initiators for radical routes.

Verification / Alternative check:
Polymerisation handbooks list decomposition kinetics of peroxides/azo initiators and their half-life temperatures for process design.

Why Other Options Are Wrong:
Acids do not decompose to radicals under normal polymerisation conditions.

Common Pitfalls:
Confusing radical and ionic polymerisation mechanisms.

Final Answer:
Organic peroxides