Industrial manufacture of styrene–butadiene rubber (SBR): which polymerisation route is most widely used commercially?

Introduction / Context:
SBR is a workhorse synthetic elastomer used in tyres, footwear, and many rubber goods. The production route strongly affects molecular weight distribution, branching, and microstructure, which in turn govern processing and performance. Identifying the mainstream route is a frequent exam topic in polymer technology.

Given Data / Assumptions:

• Large-scale SBR production aims for controllable particle size and heat removal.
• Emulsion systems offer good control over kinetics and morphology.

Concept / Approach:
Commercial SBR is predominantly made by emulsion polymerisation (cold or hot), where monomers are dispersed in water with surfactants and polymerised using free-radical initiators. This process manages exotherms effectively, produces latex amenable to coagulation, and allows tuning of properties. Solution SBR exists for specialty grades (e.g., improved tire performance), but the classical and historically dominant route is emulsion polymerisation.

Step-by-Step Solution:

Verification / Alternative check:
Industry overviews consistently identify emulsion SBR (E-SBR) as the principal commodity process, with solution SBR (S-SBR) filling performance niches.

Why Other Options Are Wrong:

• Bulk/suspension: not standard for SBR; heat and viscosity management are challenging.
• Solution: important but not the classical mass-production route in exam context.

Common Pitfalls:
Confusing the growing role of S-SBR in modern tires with the historical “most widely used” process; exams typically expect emulsion.

Final Answer:
Emulsion polymerisation