Problem 55 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is an elastomer? (a) Dacron (b) Melamine (c) vulcanized rubber (d) polystyrene

Step-by-Step Solution

Answer

(c) Vulcanized rubber is an elastomer.

Step 1: Understand Elastomers

Elastomers are polymers that exhibit elastic properties, meaning they can be stretched significantly and will return to their original shape. These materials have amorphous structures with intermolecular forces that allow them to be flexible and stretchy.

Step 2: Analyze the Options

Review each of the options given: (a) Dacron is a polyester fiber known for strength, not elasticity. (b) Melamine is a thermosetting plastic known for its durability and heat resistance, not elasticity. (c) Vulcanized rubber is a form of rubber that has been treated with sulfur to improve elasticity and strength. (d) Polystyrene is a hard and brittle thermoplastic used for rigid products.

Step 3: Identify the Elastomer

Among the options, consider the properties described in Step 1. Vulcanized rubber is the option that matches the defining properties of elastomers. It is known for its significant elasticity, making it suitable for products like tires and seals.

Key Concepts

Vulcanized Rubber

Vulcanized rubber is a specially treated form of natural rubber that is commonly used in many industries due to its enhanced properties. This process, known as vulcanization, involves adding sulfur or other equivalent curatives to raw rubber. The addition creates cross-links between the polymer chains, resulting in a material that is more durable, elastic, and resistant to changes in temperature.

The vulcanization process was invented by Charles Goodyear in the 19th century. His discovery drastically improved the performance of rubber by preventing it from becoming sticky and brittle. This makes vulcanized rubber ideal for products like car tires, which must perform well under various conditions. The elasticity and toughness provided by vulcanization enable rubber to revert to its original shape after being stretched or compressed.

Overall, vulcanized rubber exemplifies the properties of elastomers, offering significant elasticity and maintaining these properties over a broad range of temperatures and usage scenarios.

Polymer Properties

Polymers are large, chain-like molecules made up of repeating units called monomers. These substances are remarkably versatile, exhibiting a broad range of physical properties based on their chemical composition and molecular structure. The nature of these properties can vary significantly and are crucial in determining their applications in everyday life.

• Flexibility: Depending on the polymer, these materials can be very flexible, like rubber, or very rigid, like polystyrene.
• Strength: Certain polymers, such as those found in Kevlar, are known for their exceptional strength and are used in high-stress applications.
• Thermal Resistance: Polymers like melamine can withstand high temperatures, making them ideal for use in kitchenware and surfaces.

These varying properties dictate the specific function and suitability of each polymer in terms of industrial and consumer applications. By understanding polymer properties, scientists and engineers can manipulate them to create materials that specifically meet the needs of a project.

Elasticity in Materials

Elasticity refers to the ability of a material to resume its normal shape after being stretched or compressed. This property is paramount in elastomers, which are specially designed to exhibit significant elasticity. Unlike more rigid materials, elastomers like vulcanized rubber can stretch considerably before returning to their original shape once the stressing force is removed.

Elasticity in materials depends on several factors, including the arrangement of molecules within the material and the nature of the intermolecular forces present. In elastomers, the polymer chains are configured in such a way that they can easily extend and contract without breaking. This flexibility is what allows materials like rubber bands to be so stretchy and pliable.

Overall, elasticity is a critical property for materials that require durability and flexibility, and it plays a crucial role in numerous applications, from everyday items like clothing elastics to industrial components in machinery and vehicles.