Polymer materials – SBR versus natural rubber properties Compared to natural rubber, styrene–butadiene rubber (SBR) generally shows which of the following performance differences?
-
APoorer tensile strength.
-
Bpoorer resistance to oxidation.
-
Cgreater amount of heat build-up under heavy loading.
-
Dall (a), (b) and (c).
Answer
Correct Answer: all (a), (b) and (c).
Explanation
Introduction / Context:SBR is a widely used synthetic rubber in tires and general-purpose goods. Comparing it to natural rubber highlights trade-offs that guide material selection, compounding, and service environment decisions.
Given Data / Assumptions:
- SBR (styrene–butadiene) versus NR (cis-1,4-polyisoprene).
- Unfilled, unreinforced baseline comparison under similar test conditions.
- Focus on tensile strength, oxidative resistance, and heat build-up (hysteresis).
Concept / Approach:Natural rubber exhibits exceptional strain-induced crystallization, delivering higher tensile strength and tear resistance. SBR lacks strong crystallization under strain; its oxidative stability is also lower without antioxidants. SBR tends to have higher hysteresis, generating more heat under cyclic loading than NR, which is critical for tire temperature rise.
Step-by-Step Solution:
Compare tensile behavior: NR > SBR in tensile strength → SBR is poorer.Assess oxidation: NR with natural antioxidants still often outperforms base SBR; SBR needs stabilizers → poorer oxidation resistance.Evaluate heat build-up: SBR higher hysteresis → greater heat under heavy loading.Verification / Alternative check:Standard property tables for vulcanizates show NR’s superior tensile/tear and lower hysteresis versus general-purpose SBR, confirming all three statements are true simultaneously.
Why Other Options Are Wrong:Options (a), (b), and (c) each capture a true statement; hence the combined option ‘‘all (a), (b) and (c)’’ is most correct.
Common Pitfalls:Overgeneralizing after compounding: fillers (e.g., carbon black), oils, and antioxidants can significantly modify performance; the baseline material tendencies are as stated.
Final Answer:all (a), (b) and (c).