Problem 2 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Which of the following is a thermosetting polymer? [Main April 12, 2019 (I)] (a) Bakelite (b) Buns-N (c) Nylon 6 (d) PVC

Step-by-Step Solution

Answer

(a) Bakelite is the thermosetting polymer.

Step 1: Understanding the Question

We need to identify which of the given options is a thermosetting polymer. A thermosetting polymer is a polymer that becomes irreversibly hardened upon curing and cannot be melted or remolded.

Step 2: Analyzing the Options

Examine each option and relate it to the characteristics of thermosetting polymers: (a) Bakelite: Known for its heat resistance and electrical insulating properties, Bakelite is a well-known thermosetting polymer, used in electrical insulators and kitchenware. (b) Buna-N: This is a synthetic rubber, a thermoplastic elastomer known also as Nitrile rubber. It is not a thermosetting polymer. (c) Nylon 6: A type of polyamide commonly used in textiles and plastics, which is a thermoplastic polymer, not thermosetting. (d) PVC: Polyvinyl chloride is a common thermoplastic polymer used in pipes, cables, and more, but it is not thermosetting.

Step 3: Checking Against Definitions

Verify that Bakelite meets all thermosetting polymer requirements: it is formed from a formaldehyde condensation process and hardens irreversibly upon heating, making it a classic example of a thermosetting polymer.

Step 4: Selecting the Correct Answer

Based on the analysis, Bakelite (option a) is the only thermosetting polymer among the choices given.

Key Concepts

Bakelite

Bakelite is one of the earliest and most influential synthetic polymers, first invented in 1907 by Belgian chemist Leo Baekeland. This material is a true thermosetting polymer. It becomes permanently hard and rigid when it is cured, meaning it cannot be reshaped or melted after its initial formation. Bakelite is created through a condensation reaction between phenol and formaldehyde.

This characteristic makes Bakelite exceptionally valuable for applications requiring durability and heat resistance. Because of its electrical insulating properties, it is widely used in making switches, sockets, and household electrical appliances. Furthermore, it was historically popular for crafting items like phone casings and radio housings. Its ability to withstand high temperatures without deforming ensures its continued use in various industrial applications today.

Properties of Thermosetting Polymers

Thermosetting polymers, also known as thermosets, possess unique properties that differentiate them from thermoplastics. Unlike thermoplastic polymers, thermosets cannot be melted and re-molded. Here are some notable characteristics:

• Heat Resistance: Thermosetting polymers can withstand higher temperatures, making them suitable for applications that involve heat exposure.
• Durability: Once hardened, these materials are incredibly tough and resistant to wear.
• Electrical Insulation: Many thermosets, like Bakelite, are excellent electrical insulators, which make them ideal for electrical and electronic uses.
• Chemical Resistance: Thermosets often resist chemicals better than thermoplastics, making them suitable for industrial chemicals.
• Rigidity: After curing, thermosets become very rigid, which is advantageous for structural components.

These properties make thermosetting polymers essential in a variety of fields where materials need to perform under stress and high temperatures.

Examples of Thermosetting Polymers

Besides Bakelite, there are several other well-known thermosetting polymers with various applications:

• Epoxy Resins: Used extensively in adhesives, coatings, and composite materials due to their strong adhesive properties and resistance to chemicals.
• Melamine Formaldehyde: Commonly found in household items like dinnerware and laminates due to its hardness and durability.
• Urea Formaldehyde: Used in adhesives, finishes, and molding compounds, providing benefits in cabinet and furniture making.
• Polyester Resins: Applied in boat building and automotive components for their strength and corrosion resistance.

These examples highlight the diverse uses of thermosetting polymers across various industries, from everyday household items to critical infrastructure components.