Question

Molecular forces and chemical bonding in polymers

Answer 1

Answer:

✍️Molecular Forces in Polymers

Depending upon the inter-molecular forces between monomer molecules, the polymers have been classified into four types:

•Elastomers

•Fibers

•Thermoplastics

•Thermosetting

•Elastomers

✍️In case of elastomers, the polymer chains are held together by weak van der waals forces. Due to weak forces, the polymers can be easily stretched on applying small stress and they regain their original shape when the stress is removed. This is due to the presence of few cross links between the chains, which help the polymer to retract to its original position after the force is removed, as in vulcanized rubber.

The most important example of elastomer is natural rubber.

✍️Fibres

These are the polymers which have strong inter-molecular forces between the chains. These forces are either hydrogen bonds or dipole-dipole interactions. Because of the strong forces, the chains are closely packed, giving them high tensile strength and less elasticity. These polymers can be drawn into long, thin and thread like fibres and therefore can be woven into fabrics. The common examples are nylon-66, dacron, and silk.

✍️Thermoplastics

These are linear polymers with very few cross linkages or no cross linkages at all. The polymeric chains are held by weak van der waals forces and slide over one another. Due to lack of cross linkages these polymers soften on heating and harden or become rigid on cooling. Thus they can be moulded to any shape. Polythene, PVC, polystyrene are addition type thermoplastics and Terylene, nylon are condensation type thermoplastics.

✍️Plasticizers: Certain plastics do not soften much on heating. These can be easily softened by the addition of some organic compounds which are called plasticizers. For example, polyvinyl chloride (PVC) is very stiff and hard but is made soft by adding di-n-butylphthalate (a plasticizer). Some other common plasticizers are dialkyl phthalates and cresyl phthalate.

✍️Thermosetting Polymers

Usually thermosetting polymer can be heated only once when it permanently sets into a solid which can not be remelted and re-moulded. Thermosetting polymers are produced from relatively low molecular mass semi fluid polymers (called polymers) which on heating develop extensive cross-linking by themselves or by adding some cross-linking agents and become infusible and insoluble hard mass. The cross links hold the molecules in place so that heating does not allow them to move freely. Therefore, a thermosetting plastic is cross linked and is permanently rigid. The common examples are bakelite melamine and formaldehyde resin.

✔️Hope it will be helpful.✔️

Answer 2

Explanation:

Molecular forces:

• These polymers exhibit strong molecular interactions between their chains.
• Dipole-dipole interactions or hydrogen bonding are the two types of forces involved.
• The chains are tightly packed as a result of the tremendous forces, giving them a high tensile strength and low flexibility.
• In contrast to the intermolecular forces between tiny molecules, the intermolecular forces between polymer molecules are strong.
• This implies that materials with large molecules melt at lower temperatures than those with polymers.
• Even at room temperature, they are solids.

Chemical bonding:

• The enormously lengthy molecules that make up polymers have carbon chain sequences.
• They also are joined by extremely powerful covalent bonds.
• Compared to smaller simple molecules, lengthy chains have stronger intermolecular forces.
• In comparison to many other organic compounds, polymers have a greater melting point.

In comparison to many other organic compounds, polymers have a greater melting point.#SPJ2