Elastomers – comparing SBR (styrene–butadiene rubber) with natural rubber: which combined performance differences are typically observed under service conditions?

Introduction:Styrene–butadiene rubber (SBR, Buna-S) is the most widely used synthetic elastomer. This question assesses knowledge of how SBR compares to natural rubber (NR) in key mechanical and dynamic properties under comparable compounding levels.

Given Data / Assumptions:

• SBR and NR are compared at typical, similar filler and cure conditions.
• Service involves tensile loading and dynamic flexing (heat build-up).
• We consider general trends, not specialty grades.

Concept / Approach:NR exhibits outstanding strain-induced crystallization, giving it higher tensile and tear strength and superior fatigue resistance. SBR lacks the same level of crystallization and typically shows higher hysteresis, leading to more heat build-up under heavy cyclic loads.

Step-by-Step Solution:Compare tensile properties: NR > SBR for tensile and tear due to strain-induced crystallization.Assess resistance/aging: NR often shows better cut-growth and fatigue crack resistance; SBR may need reinforcing systems to approach NR.Evaluate dynamic heat: SBR generally exhibits higher hysteresis → greater heat build-up under heavy loading.Hence, all listed differences apply.

Verification / Alternative check:Standard rubber handbooks list NR with higher green strength and resilience; SBR is chosen for cost, abrasion resistance, and good wet traction when compounded, but not for superior tensile vs. NR.

Why Other Options Are Wrong:

• Each of (a), (b), (c) is independently true; the comprehensive answer is all of the above.
• Claiming SBR has universally higher green strength and resilience than NR is incorrect in general practice.

Common Pitfalls:Overgeneralizing based on certain oil-extended or solution-SBR grades; base property trends still favor NR in tensile/tear and lower heat build-up.

Final Answer:All of the above