Problem 156 - Advanced Problems in Organic Chemistry for Competitive Examinations

Question

Which one of the following is a thermosetting polymer? (a) SBR (b) Nylon-6, (c) Bakelite (d) Nylon-6

Step-by-Step Solution

Answer

The thermosetting polymer is Bakelite (option c).

Step 1: Identify the Options

We are given four options: SBR (Styrene Butadiene Rubber), Nylon-6, Bakelite, and Nylon-6 again. We need to determine which among these is a thermosetting polymer.

Step 2: Understand Thermosetting Polymers

Thermosetting polymers are materials that irreversibly cure. This implies that once they are set, they cannot be melted or remolded. They are usually hard and heat resistant due to their extensive cross-linking.

Step 3: Determine SBR

SBR is a synthetic rubber, which means it is an elastomer rather than a thermoset. Elastomers are typically flexible and not cross-linked like thermosetting polymers.

Step 4: Determine Nylon-6

Nylon-6 is a type of polyamide, which is a thermoplastic. Thermoplastics can be remolded and are not thermosetting. Since both options (b) and (d) are Nylon-6, they cannot be thermosetting.

Step 5: Determine Bakelite

Bakelite is a phenol formaldehyde resin and is known as the first synthetic plastic. It is a classic example of a thermosetting polymer due to its irreversible hardening. Once it has set, it cannot be melted and remolded.

Step 6: Conclusion on the Correct Option

Based on the analysis, Bakelite is the only option that fits the description of a thermosetting polymer, making option (c) correct.

Key Concepts

Thermosetting Polymers

Thermosetting polymers are a fascinating category of materials that become permanently rigid during the curing process. This is due to a phenomenon known as cross-linking, where polymer chains are interconnected in a three-dimensional network. Once set, these polymers cannot be melted or reshaped, making them ideal for applications requiring heat resistance and structural integrity.

A few important traits characterize thermosetting polymers:

• They typically have high thermal, chemical, and electrical resistance, which makes them suitable for tough environments.
• The irreversible setting process results in a material that is strong and durable.
• Common uses include electronic appliances and adhesive applications, where permanent bonding is essential.

These polymers often contrast with thermoplastics, which can be reheated and remolded, presenting them as ideal solutions for unique industrial challenges.

Synthetic Polymers

Synthetic polymers are human-made polymers, developed largely due to industrial and inventive needs. Unlike natural polymers, which are found in materials like silk or rubber, synthetic ones are created through synthetic reactions and processes.

There are several distinct types:

• Thermoplastics, which can be remolded with heat.
• Elastomers, which are flexible and stretchy, like synthetic rubbers.
• Thermosetting polymers, which harden and set permanently, like Bakelite.

Synthetic polymers boast wide applications, including in textiles, packaging, and coatings. Their inventiveness lies in tailoring properties to specific needs, providing versatility that often exceeds natural alternatives. This flexibility in design has revolutionized numerous industries.

Bakelite Properties

Bakelite stands out as the original synthetic plastic, marking a significant milestone in materials science. Developed in the early 20th century, Bakelite is a thermosetting polymer made from phenol and formaldehyde. Its properties are remarkable due to the inherent strength and durability once it cures.

Notable properties of Bakelite include:

• High resistance to heat and chemicals, making it ideal for electrical insulators and cookware handles.
• Excellent electrical non-conductivity, which makes it a prime choice for electronic applications.
• Ability to retain rigidity and form under stress, adding to its utility in heavy-duty applications.

Bakelite's advent shuffled the landscape of synthetic materials, motivating further innovations and signifying the transition from natural to modern high-performance materials.