Question

Regarding cross-linked or network polymers, which of the following statements is incorrect ?

• A. They contain strong covalent bonds in their polymer chains.
• B. They contain covalent bonds between various linear polymer chains.
• C. Examples are bakelite and melamine
• D. They are formed from bi- and tri-functional monomers

Answer 1

The Correct Option is A

To determine the incorrect statement regarding cross-linked or network polymers, let's examine each option with respect to the characteristics and structure of these polymers.

1. The statement "They contain strong covalent bonds in their polymer chains." is incorrect. In cross-linked or network polymers, the strong covalent bonds are primarily between the linear polymer chains, creating a three-dimensional network structure. The covalent bonds in the polymer chains are typical in all polymers (whether linear or cross-linked) and not a distinguishing feature of cross-linked polymers.
2. The statement "They contain covalent bonds between various linear polymer chains." is correct. This is a defining feature of cross-linked polymers. They have covalent connections between the polymer chains, which provide them with unique structural and mechanical properties, such as higher resistance to solvents and thermal stability.
3. The statement "Examples are bakelite and melamine." is correct. Both bakelite and melamine are well-known examples of cross-linked polymers. They are formed through polymerization where the monomer units create a network-type structure (Bakelite is a phenol-formaldehyde resin, and melamine is a formaldehyde resin).
4. The statement "They are formed from bi- and tri-functional monomers." is correct. Cross-linked polymers are often formed from monomers that can create more than one bond, leading to a network structure. Bi-functional and tri-functional monomers are commonly used for this purpose.

Therefore, the incorrect statement regarding cross-linked or network polymers is "They contain strong covalent bonds in their polymer chains." This statement incorrectly emphasizes the covalent bonds within the chains instead of between them.