Problem 17 - Chemistry in 30 days

Question

Which of the following is a polyámide ? (a) Teflon (b) Nylon-6,6 (c) Terylene (d) Bakelite

Step-by-Step Solution

Answer

The polyamide is Nylon-6,6.

Step 1: Understand Polymers

Polyamides are a type of polymer that include repeated amide linkages between their monomer units. An amide linkage is characterized by the functional group \(-CONH-\). Polymers are large molecules formed by connecting smaller molecules (monomers) through chemical bonds.

Step 2: Analyze Each Option

Examine each given option to identify which is a polyamide based on their chemical composition: - **Teflon** is a polymer consisting of tetrafluoroethylene; it is not a polyamide, but a fluoropolymer. - **Nylon-6,6** is a synthetic polymer with amide linkages; it is a known polyamide. - **Terylene** is a polyester, made from ethylene glycol and terephthalic acid; it does not have amide linkages. - **Bakelite** is a phenol-formaldehyde resin; it lacks amide linkages as well.

Step 3: Identify Polyamide

From the analysis, Nylon-6,6 is the polymer with repeated amide linkages. Therefore, among the given options, Nylon-6,6 is a polyamide.

Key Concepts

Understanding Polyamides

Polyamides are fascinating polymers widely used due to their strength and durability. These are composed of repeating units connected by specific chemical bonds called "amide linkages." What makes polyamides unique is the presence of the amide group \(-CONH-\). This group forms when a carboxylic acid group (\(-COOH\)) reacts with an amine group (\(-NH_2\)). Polyamides can be found both naturally and synthetically. Natural polyamides include proteins such as silk and wool. On the other hand, synthetic polyamides, such as Nylon, have become essential in various industrial applications. With their ability to form flexible yet strong fibers, polyamides play a significant role in textiles and many other fields.

The Role of Amide Linkages

The backbone of polyamides is the amide linkage, an integral part of their structure and properties. Amide linkages are formed during a condensation reaction, where a water molecule is released. This bond formation occurs when a carboxylic acid group from one monomer reacts with an amine group from another monomer. The result is the creation of the amide linkage \(-CONH-\), giving polyamides their characteristic structure. These linkages are essential for the stability and resilience of polyamide materials, as they contribute to:

• High melting points
• Excellent mechanical strength
• Resistance to wear and chemical degradation

The robust nature of amide linkages allows polyamides to be used in demanding applications, from construction materials to high-strength ropes and automotive parts.

Exploring Nylon-6,6

Nylon-6,6 is a well-known synthetic polyamide that consists of repeating units connected by amide linkages. It is formed through a polycondensation reaction between two specific monomers: hexamethylenediamine (\(NH_2\,(CH_2)_6\,NH_2\)) and adipic acid (\(HOOC\,(CH_2)_4\,COOH\)). During the reaction, each carboxylic acid group of adipic acid bonds with an amine group of hexamethylenediamine, resulting in the formation of the amide \(-CONH-\) linkage and water as a byproduct. This structure gives Nylon-6,6 its famed properties:

• Excellent strength and durability
• High resistance to abrasion and chemicals
• Ability to be molded into various shapes

These properties enable Nylon-6,6 to be used extensively in fabric for clothing, carpets, tires, and even mechanical parts in machinery.