Which of the following is used in making automobile tyres and footwear?

Vulcanized rubber

The correct answer is option 4. Vulcanized rubber.

Vulcanized rubber is a form of rubber that has undergone a chemical process called vulcanization, named after the Roman god of fire, Vulcan. This process involves heating natural rubber or synthetic rubber with sulfur or other additives to improve its properties.

Here is how the vulcanization process works:

1. Mixing: The process starts with mixing the raw rubber material (either natural rubber latex or synthetic rubber) with various additives such as sulfur, accelerators, and activators. These additives help initiate and control the vulcanization reaction.

2. Heating: The rubber mixture is then heated to a specific temperature, typically between 140°C to 160°C (284°F to 320°F), in a vulcanization press or autoclave. The heat causes the sulfur to react with the rubber polymer chains, forming cross-links between them.

3. Cross-linking: During vulcanization, sulfur atoms form bridges (cross-links) between adjacent polymer chains. These cross-links create a network structure within the rubber, enhancing its mechanical properties such as strength, elasticity, and resilience.

4. Cooling and Shaping: After the vulcanization process is complete, the vulcanized rubber is cooled and removed from the mold or press. It retains its new properties even after cooling down.

The vulcanization process transforms raw rubber into a material with improved properties suitable for various applications. Vulcanized rubber exhibits several advantages over raw rubber, including:

Increased strength and durability: The cross-links formed during vulcanization strengthen the rubber, making it more resistant to wear, abrasion, and degradation over time.

Enhanced elasticity and flexibility: Vulcanized rubber maintains its elasticity and flexibility over a wide range of temperatures, allowing it to withstand stretching, bending, and compression without permanent deformation.

Improved chemical and weather resistance: The cross-linked structure of vulcanized rubber provides better resistance to chemicals, oils, solvents, and environmental factors such as sunlight, ozone, and moisture.

Better adhesion: Vulcanized rubber adheres well to various substrates, allowing it to be used in applications where strong bonds are required, such as tire treads, shoe soles, and industrial seals.

Due to these advantageous properties, vulcanized rubber is widely used in a diverse range of applications, including automobile tires, footwear, conveyor belts, gaskets, seals, hoses, and industrial products. Its versatility, durability, and performance make it indispensable in many industries.