Question

Which is/are correct about kevlar here? (I) It is a polyamide (II) It is used in making buluet proof vests etc III) It is homopolymer formed by addition reaction. IV) It is polymer of terephthalic acid and 1,4 diamino benzene. (a) I, II, III (b) I, II, IV (c) II, III, IV (d) I, II, III, IV

Short answer

The correct option is (b) I, II, IV.

Step-by-step solution

Understand the Definition of Kevlar

Kevlar is a type of synthetic polymer known for its high tensile strength-to-weight ratio, making it very strong and durable. It is categorized as a polyamide.

Examine Characteristics Relevant to Bulletproof Vests

Kevlar is widely used in making bulletproof vests and other protective gear due to its strength and ability to absorb impact energy efficiently.

Analyze If Kevlar is a Result of an Addition Reaction

Kevlar is not formed by an addition reaction; it is produced using a condensation polymerization process. This involves the reaction between monomers with different functional groups, releasing a small molecule like water.

Verify Kevlar's Polymer Composition

Kevlar is a polymer made from a condensation reaction between terephthalic acid and 1,4-diaminobenzene, resulting in the formation of a strong amide bond.

Choose the Correct Answer Based on Analysis

From the analysis: - Statement I is correct (Kevlar is a polyamide). - Statement II is correct (Used in bulletproof vests). - Statement III is incorrect (It is not an addition polymer but a condensation polymer). - Statement IV is correct (Polymer of terephthalic acid and 1,4-diaminobenzene). Thus, the correct answer is option (b) I, II, IV.

Key concepts

Polyamide

Kevlar is classified as a polyamide, which is a polymer containing recurring amide groups, characterized by the linkage of carbonyl ( -CO- ) and nitrogen ( -NH- ) atoms between each mer. This structure is key to the strength and durability of materials like Kevlar.
Polyamides can be natural, such as proteins including wool and silk, or synthetic, such as nylon and Kevlar. The repeated presence of the amide linkage is significant because it forms alternating patterns of carbon and nitrogen atoms. These amide bonds create strong intermolecular forces, contributing to the resilience and toughness of polyamide-based fabrics.

Condensation Polymerization

Condensation polymerization is a process by which monomers with different functional groups react to form a polymer, releasing small molecules as byproducts like water. Unlike addition polymerization, this method results in the release of a small molecule as a byproduct, usually a molecule of water or an alcohol.
Kevlar is an example of a material formed through condensation polymerization. This occurs when the monomers, 1,4-diaminobenzene and terephthalic acid, combine to form polymer chains by eliminating water molecules. The new polymer structure contains alternating amide linkages, contributing to the unique strength of Kevlar. Understanding this process helps in grasping the molecular basis of why Kevlar's properties make it suitable for specialized uses.

Bulletproof Vests

Bulletproof vests are essential protective gear that utilizes the unique properties of Kevlar. The strength and impact resistance of Kevlar make it an ideal material for this purpose.

• High tensile strength helps to absorb impact energy from bullets, dispersing it across a wide area.
• Lightweight nature makes the vests easier to wear for extended periods, offering flexibility and comfort.
• The ability to maintain structural integrity, even under duress, provides added safety.

Thus, the use of Kevlar in bulletproof vests stems from these features, enhancing personal safety for military personnel and law enforcement officers.

Terephthalic Acid

Terephthalic acid is a crucial component in the formation of Kevlar. It provides the necessary carboxyl groups ( -COOH ) that participate in condensation polymerization.
This organic compound is a type of aromatic acid, contributing to the final structure's rigidity and strength. It is similar in chemistry to other compounds like polyethylene terephthalate (PET), commonly known as the material for plastic bottles and polyester.
Its role in the formation of Kevlar involves the repeated pairing with 1,4-diaminobenzene, forming strong covalent bonds that hold the polymer chains tightly together. This interaction between the two distinct monomers adds to Kevlar's renowned durability.

1,4-Diaminobenzene

1,4-Diaminobenzene, also known as para-phenylenediamine (PPD), acts as a reactive monomer in the formation of Kevlar. It provides amino groups ( -NH2 ), which are essential for creating the amide linkages during polymerization.
As a benzene derivative, it has a symmetrical structure which facilitates uniform polymer chain formation. The linearity of its structure allows for neat packing of the polymer chains, contributing to Kevlar's incredible strength and resistance.

• These amino groups react with the carboxyl groups of terephthalic acid, enhancing the material's toughness.
• Besides Kevlar, 1,4-diaminobenzene is also used in producing other types of fibers and plastics.

Thus, its chemical properties and role in polymerization are integral to the creation of Kevlar's highly resilient structure.