Material degradation from oxidants: Elevated ozone and smog exposure in air is especially known to cause which specific type of damage to materials?

Introduction / Context:
Ambient oxidants such as ozone are highly reactive and can attack organic materials, leading to premature aging or failure. Recognizing signature damage patterns helps in diagnosing environmental exposure problems in infrastructure and consumer goods. This question focuses on the best-known effect of ozone-rich smog on materials.

Given Data / Assumptions:

• Consider common ambient ozone levels found in polluted urban air.
• Exposure occurs over weeks to years, not laboratory extremes.
• Materials include elastomers, paper, textiles, and electrical components.

Concept / Approach:
Ozone reacts with unsaturated bonds in elastomers (e.g., natural rubber, some synthetic rubbers), causing chain scission. Under stress, microcracks initiate and propagate, a phenomenon known as ozone cracking. This manifests as characteristic surface cracks on tires, seals, and gaskets. While ozone can also contribute to fading dyes and affecting paper properties, the most diagnostic and severe everyday effect is cracking of rubber goods. High-voltage insulators are more affected by contaminants, moisture, and tracking than by ordinary ambient ozone alone.

Step-by-Step Solution:
Identify which material class has strong, well-documented susceptibility to ozone: elastomers.Recall the mechanism: attack on double bonds → chain scission → cracks under strain.Select “cracking of rubber products.”

Verification / Alternative check:
Maintenance guidance for seals and tires recommends ozone-resistant compounds or protective waxes/antiozonants in smog-prone regions, reaffirming this is the hallmark effect.

Why Other Options Are Wrong:
Paper embrittlement: Primarily due to acid hydrolysis and aging; ozone plays a lesser role.Dye fading: Possible, but sunlight and oxidants both contribute; less specific than rubber cracking.Electrical insulator damage: Typically from tracking/pollution flashover rather than ambient ozone alone.

Common Pitfalls:

• Attributing any material degradation to “smog” generically; mechanisms differ by material.
• Ignoring mechanical strain, which accelerates ozone cracking in elastomers.

Final Answer:
cracking of rubber products