Effect of styrene content in SBR:\nIncreasing styrene fraction during SBR copolymerisation adversely affects which property most noticeably?

Introduction / Context:
SBR properties depend on the styrene-to-butadiene ratio. As styrene content rises, the rubber becomes harder and more plastic-like; dynamic properties such as resilience and low-temperature flexibility deteriorate. Understanding this trade-off guides compound selection for tires and mechanical goods.

Given Data / Assumptions:

• Higher styrene raises glass transition temperature and hardness.
• Dynamic elastic recovery (resilience) tends to decrease with higher Tg.

Concept / Approach:
Resilience measures the ability of a rubber to return energy elastically. When styrene content increases, Tg shifts upward, internal friction rises, and resilience decreases. Percent elongation also tends to drop, but resilience is classically highlighted as the adversely affected property in many question banks, because it is central to dynamic service (e.g., rolling resistance and heat buildup).

Step-by-Step Solution:

Verification / Alternative check:
Rubber compounding texts show resilience decreasing with increasing styrene content in SBR grades.

Why Other Options Are Wrong:

• Percent elongation may also reduce, but resilience is the definitive dynamic metric affected.
• Freezing point is not the standard property discussed here.
• Strength/abrasion: may vary but not the primary adverse effect attributed to styrene increase.

Common Pitfalls:
Equating hardness increases with improved dynamic performance; harder does not mean more resilient.

Final Answer:
Resilience