Composition, Properties and Uses of Polymer Questions in English

(A) The polydispersity index $(PDI)$ is defined as the ratio of weight average molecular weight to number average molecular weight.
$PDI = \frac{\bar{M}_w}{\bar{M}_n}$
Given:
$\bar{M}_w = 60000$
$\bar{M}_n = 40000$
$PDI = \frac{60000}{40000} = 1.5$
Since $1.5 > 1$, the polydispersity index of the polymer is $>1$.

(B) The weight average molecular mass is calculated using the formula: $\bar{M}_w = \frac{\sum n_i M_i^2}{\sum n_i M_i}$
Given:
$n_1 = 3, M_1 = 1000$
$n_2 = 3, M_2 = 500$
$n_3 = 4, M_3 = 200$
Numerator: $(3 \times 1000^2) + (3 \times 500^2) + (4 \times 200^2) = 3,000,000 + 750,000 + 160,000 = 3,910,000$
Denominator: $(3 \times 1000) + (3 \times 500) + (4 \times 200) = 3000 + 1500 + 800 = 5300$
$\bar{M}_w = \frac{3,910,000}{5300} \approx 737.7$

(B) The ratio of weight average molecular weight to the number average molecular weight is defined as the poly dispersity index $(PDI)$.
$PDI = \frac{\bar{M}_w}{\bar{M}_n}$
where,
$\bar{M}_w = \text{weight average molecular weight}$
$\bar{M}_n = \text{number average molecular weight}$
For natural monodispersed polymers, $PDI = 1$, whereas for synthetic polymers, $PDI > 1$.

(D) Orlon is also known as polyacrylonitrile $(PAN)$.
The monomer used for the preparation of orlon is acrylonitrile, which has the chemical formula $CH_2=CH-CN$.

(D) $Teflon$ is a synthetic fluoropolymer of tetrafluoroethylene.
Its chemical formula is $(C_2F_4)_n$.
The monomer unit is tetrafluoroethylene, which is $CF_2 = CF_2$.
Therefore, the correct option is $D$.

(B) Step $1$: $Orlon$ is a synthetic polymer also known as polyacrylonitrile $(PAN)$.
Step $2$: The polymerization of acrylonitrile $(CH_2=CH-CN)$ leads to the formation of $Orlon$.
Step $3$: Therefore, the monomer used to prepare $Orlon$ is acrylonitrile.

(C) $1$. Vulcanization is a chemical process in which natural rubber is heated with sulfur.
$2$. This process creates cross-links between the polymer chains of rubber.
$3$. These cross-links significantly increase the mechanical properties of rubber, specifically its tensile strength, elasticity, and durability.
$4$. Therefore, vulcanization improves the tensile strength of rubber.

(B) $1$. $Dacron$ (also known as $Terylene$) is a polyester polymer.
$2$. It is formed by the condensation polymerization of ethylene glycol $(HO-CH_2-CH_2-OH)$ and terephthalic acid $(C_6H_4(COOH)_2)$.
$3$. During the formation of the polymer, the carboxylic acid group of the acid and the hydroxyl group of the alcohol react to form an ester linkage $(-COO-)$.
$4$. Therefore, $Dacron$ contains an ester linkage.

(C) $1$. $Bakelite$ is a thermosetting polymer formed by the condensation polymerization of $Phenol$ and $Formaldehyde$.
$2$. $Methanal$ is the $IUPAC$ name for $Formaldehyde$ $(HCHO)$.
$3$. The reaction involves the initial formation of $o$- or $p$-hydroxymethylphenol derivatives, which then undergo cross-linking to form the polymer.
$4$. Therefore, the correct monomers are $Phenol$ and $Methanal$.

(B) Step $1$: Natural rubber is a linear polymer of isoprene and is soft and sticky.
Step $2$: To improve its physical properties, it is heated with sulphur. This process is known as vulcanization.
Step $3$: During vulcanization, sulphur forms cross-links at the reactive sites of double bonds, which makes the rubber harder, stronger, and more durable.
Step $4$: Therefore, vulcanization is the process that develops cross-links in elastomers.

(B) Step $1$: Identify the monomers of $Buna-S$. The name $Buna-S$ is derived from $Bu$ (for $1, 3$-butadiene), $na$ (for sodium, which acts as a catalyst), and $S$ (for styrene).
Step $2$: The polymerization reaction involves the copolymerization of $1, 3$-butadiene $(CH_2=CH-CH=CH_2)$ and styrene $(C_6H_5CH=CH_2)$.
Step $3$: Therefore, $Buna-S$ is prepared from $1, 3$-butadiene and styrene.

(B) Step $1$: Identify the properties required for nonstick cookware, such as high thermal stability and chemical inertness.
Step $2$: $Teflon$ (Polytetrafluoroethylene, $PTFE$) is a synthetic fluoropolymer of tetrafluoroethylene that has these properties.
Step $3$: Due to its low coefficient of friction and non-stick nature, it is widely used as a coating for nonstick pans and other cookware.
Step $4$: Therefore, the correct polymer is $Teflon$.

(D) $1$. Plastic bottles used for storing cooking oil and carbonated drinks are typically made from $Polyethylene \ terephthalate$ ($PET$ or $PETE$).
$2$. $PET$ is a thermoplastic polymer resin of the polyester family, known for its clarity, strength, and chemical resistance to oils and food products.
$3$. $PVC$ is used for pipes, $PS$ for disposable containers, and $LDPE$ for flexible films and bags.
$4$. Therefore, the correct option is $D$.

(C) $1$. Raincoats are made from water-resistant materials.
$2$. Polyvinyl chloride $(PVC)$, represented by the structure $- [CH_2 - CH(Cl)]_n -$, is a widely used thermoplastic polymer known for its water-repellent properties.
$3$. It is extensively used in the manufacturing of raincoats, handbags, water pipes, and floor coverings.
$4$. Therefore, the correct option is $C$.

(A) The preparation of viscose rayon involves several steps. The first stage is the steeping of cellulose (usually wood pulp) in a $17-20\%$ solution of $NaOH$ to form alkali cellulose.
Step $1$: Steeping (Formation of alkali cellulose).
Step $2$: Pressing.
Step $3$: Shredding.
Step $4$: Aging.
Step $5$: Xanthation.
Step $6$: Dissolving.
Step $7$: Ripening.
Therefore, the first stage is the treatment with $NaOH$.

(B) Step $1$: Disposable cups and plates are typically made from materials that are lightweight, inexpensive, and easy to mold.
Step $2$: $Polystyrene$ (specifically expanded polystyrene or $EPS$) is widely used for manufacturing disposable food service items like cups, plates, and containers due to its excellent insulating properties and low cost.
Step $3$: Therefore, the correct polymer is $Polystyrene$.

(B) $1$. $HDPE$ (High-Density Polyethylene) is a thermoplastic polymer known for its high strength-to-density ratio.
$2$. Due to its rigidity and chemical resistance, it is widely used in the manufacturing of blow-molded products such as shampoo bottles, detergent bottles, and milk jugs.
$3$. Shopping bags are typically made from $LDPE$ (Low-Density Polyethylene), while carpets are often made from fibers like nylon or polypropylene.
$4$. Therefore, the correct use of $HDPE$ among the given options is to prepare shampoo bottles.

(D) $LDP$ stands for Low Density Polyethene.
It is a tough, flexible, and chemically inert polymer.
It is primarily used in the manufacture of squeeze bottles, toys, and flexible pipes.
Buckets are typically made from $HDP$ (High Density Polyethene).
Pipes for irrigation are also made from $HDP$.
Non-stick cookware uses $PTFE$ (Teflon).
Therefore, the correct use of $LDP$ is for making squeeze bottles and flexible pipes.

(A) $1$. $HDPE$ (High-Density Polyethylene) is a strong, durable, and chemical-resistant polymer.
$2$. Due to its high density and rigidity, it is widely used for manufacturing containers such as shampoo bottles, detergent bottles, and milk jugs.
$3$. $LDPE$ is more flexible and used for films, while $PP$ and $PS$ have different specific applications.

(B) Step $1$: $Teflon$ is polytetrafluoroethylene $(PTFE)$.
Step $2$: The monomer of $Teflon$ is tetrafluoroethene $(CF_2=CF_2)$.
Step $3$: In this polymer, all hydrogen atoms of the ethene backbone are replaced by fluorine atoms, making it a fully fluorinated polymer.
Step $4$: $PVC$ is polyvinyl chloride, $Neoprene$ is polychloroprene, and $Buna-S$ is a copolymer of $1,3-butadiene$ and $styrene$, none of which are fully fluorinated.

(B) Step $1$: Identify the chemical nature of each polymer.
Step $2$: $Glyptal$ is a polyester formed by the condensation of ethylene glycol and phthalic acid.
Step $3$: $PHBV$ (poly-$\beta$-hydroxybutyrate-co-$\beta$-hydroxyvalerate) is a biodegradable polyester.
Step $4$: $Dacron$ (Terylene) is a well-known polyester formed from ethylene glycol and terephthalic acid.
Step $5$: $Novolac$ is a linear polymer formed by the condensation of phenol and formaldehyde, which is a phenol-formaldehyde resin, not a polyester.
Step $6$: Therefore, $Novolac$ is $NOT$ a polyester polymer.

(B) Viscose rayon is a regenerated fibre. It is obtained from naturally occurring polymers. The starting material used for the production of viscose rayon is purified cellulose, which is typically derived from wood pulp or cotton linters.

(D) $Terylene$ is a polyester fibre obtained by the condensation polymerization of ethylene glycol and terephthalic acid. It is also known as $Dacron$ or $Mylar$.

(C) Step $1$: $Terylene$ (also known as $Dacron$) is a condensation polymer.
Step $2$: It is prepared by the polymerization of $Ethane-1,2-diol$ (ethylene glycol) and $Benzene-1,4-dicarboxylic$ acid (terephthalic acid).
Step $3$: The reaction involves the loss of water molecules to form an ester linkage, resulting in the polyester $Terylene$.

(A) $1$. Thermosetting polymers are cross-linked polymers that become hard and infusible on heating and cannot be remolded.
$2$. $Urea-formaldehyde$ resin is a classic example of a thermosetting polymer.
$3$. $Polystyrene$, $Buna-S$, and $Terylene$ are thermoplastic polymers or elastomers, which can be softened or reshaped upon heating.

(C) Step $1$: Urea-formaldehyde resin is a thermosetting polymer formed by the condensation polymerization of urea and formaldehyde.
Step $2$: The chemical structure of the repeating unit in urea-formaldehyde resin is $[NH - CO - NH - CH_2]_n$.
Step $3$: Option $(A)$ represents polyacrylamide, $(B)$ represents polystyrene, $(C)$ represents urea-formaldehyde resin, and $(D)$ represents Nylon-$6$.
Step $4$: Therefore, the correct option is $(C)$.

(A) Step $1$: Identify the nature of the given polymers. $PVC$, $Polystyrene$, and $PTFE$ are thermoplastic polymers, which soften on heating and harden on cooling.
Step $2$: $Bakelite$ is a phenol-formaldehyde resin. It is formed by the condensation polymerization of phenol and formaldehyde, resulting in a highly cross-linked structure.
Step $3$: Because of this cross-linked network, $Bakelite$ cannot be reshaped upon heating, making it a thermosetting polymer.
Step $4$: Therefore, $Bakelite$ is the correct answer.