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Regarding cross linked or network polymers, which of the following statements is incorrect?
This question has multiple correct options
A ) Examples are bakelite and melamine.
B ) They contain covalent bonds between linear polymer chains.
C ) They contain strong covalent bonds in their polymer chains.
D ) They are formed from bi and tri functional monomers.

Last updated date: 13th Jun 2024
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Hint: Usually, polymers are obtained from simple covalent molecules. So all of the polymers contain strong covalent bonds. It is not possible to obtain a polymer containing only ionic bonds.

Complete answer:
> In cross linked polymers, monomer units cross link to form a three dimensional network. Examples of cross linked polymers include melamine and bakelite. These polymers are thermosetting polymers. On heating, they undergo permanent heating. Bakelite is a condensation polymer of phenol and formaldehyde. Melmac (melamine-formaldehyde resin) is the condensation polymer of Melamine with formaldehyde. Melamine is \[{\text{2,4,6 - triamine - 1,3 - 5 - triazine}}\] .
Hence, the statement A ) is a correct statement.
> Cross linked or network polymers contain covalent bonds between polymer chains. These polymer chains may or may not be linear. Hence, the option B ) is an incorrect statement.
> Network polymers contain strong covalent molecules between various monomer units. The monomers themselves contain strong covalent bonds. Hence, the option C ) is the correct statement.
> Cross linked polymers can be formed from mono, bi or trifunctional monomers. Two or more monofunctional monomers can form a bifunctional monomer. For example, in bakelite, monofunctional monomers phenol and formaldehyde are used. Hence, the option D ) is incorrect.

Hence, the options B ) and D ) represent the incorrect statements.

Note: Bakelite is used in making electrical switches. It is also used in making handles of various utensils. Melamine polymer is a non biodegradable polymer. If melamine accumulates, it will cause environmental problems. Melamine is used in high pressure laminates, overlay materials etc.