Effects of vulcanisation on rubber: which statement correctly captures a primary effect?

Introduction / Context:Vulcanisation introduces crosslinks (commonly sulfur-based) between rubber chains, transforming soft, tacky gum rubber into an elastic, resilient material with improved service properties.

Given Data / Assumptions:

• Crosslink density governs modulus, elasticity, and solvent resistance.
• Antidegradants are often added to resist ozone and oxidation.
• Oil and solvent resistance generally improves with appropriate crosslinking and polymer choice.

Concept / Approach:Crosslinks restrict chain slippage, enabling elastic recovery and higher tensile strength. They also reduce swelling in oils/solvents by limiting chain mobility. Proper compounding improves ozone/oxygen durability, not the reverse.

Step-by-Step Solution:Identify the core transformation: from plastic flow to elastic recovery due to crosslinks.Evaluate property trends: tensile strength increases; solvent/oil resistance typically increases; ozone reactivity decreases with antidegradants.Choose the statement that aligns with these fundamentals.

Verification / Alternative check:Stress–strain curves of gum vs vulcanised rubber show higher modulus and recovery post-vulcanisation.

Why Other Options Are Wrong:Tensile strength does not decrease; ozone/oxygen reactivity decreases with suitable additives; oil/solvent resistance does not decrease.

Common Pitfalls:Assuming any crosslinking reduces flexibility to brittleness—over-vulcanisation can embrittle, but correct cure enhances elasticity.

Final Answer:Converts its plasticity into elasticity (improves elastic recovery)