Which polymer is used in the manufacture of paints and lacquers?

We begin by recalling that paints and lacquers require a film-forming substance that can spread easily, dry to give a hard, glossy surface, and remain chemically inert under ordinary atmospheric conditions. Among the well-known synthetic polymers, only a few satisfy all these criteria.

Now, let us briefly examine the four polymers mentioned in the options and relate their typical applications to the requirements of paints and lacquers.

First, polyvinyl chloride (PVC) is represented by the repeating unit $$\left( -CH_2-CHCl- \right)_n$$. PVC is appreciated for its toughness and resistance to chemicals, but its common uses are in pipes, wire insulation, and flooring—not in high-quality film-forming coatings. Therefore, PVC is unsuitable for the present purpose.

Second, bakelite is a phenol-formaldehyde resin produced by the condensation of phenol and formaldehyde. Its three-dimensional network structure makes it hard, brittle, and heat-resistant. These properties make bakelite excellent for electrical switches and utensil handles, yet its brittleness prevents it from forming the flexible, glossy films needed in paints and lacquers. Hence, bakelite is also ruled out.

Third, glyptal is obtained by the condensation polymerisation of ethylene glycol $$HO-CH_2-CH_2-OH$$ with either phthalic acid $$HOOC-C_6H_4-COOH$$ or phthalic anhydride $$\displaystyle \bigl( C_6H_4(CO)_2O \bigr)$$. The general reaction may be written as

$$\underbrace{n\,HO-CH_2-CH_2-OH}_{$$ ethylene glycol $$} \;+\; \underbrace{n\,HOOC-C_6H_4-COOH}_{$$ phthalic acid $$} \;\longrightarrow\; \underbrace{\bigl[ -O-CH_2-CH_2-OOC-C_6H_4-CO- \bigr]_n}_{$$ glyptal $$} \;+\; 2n\,H_2O$$

Because glyptal molecules contain a large number of ester linkages, the resulting polymer chains can cross-link lightly, creating a viscous liquid that cures to a tough, adherent, and glossy film. These very features make glyptal resins ideal binders for surface-coating formulations such as paints, enamels, and lacquers.

Finally, polypropene (polypropylene) has the repeating unit $$\left( -CH_2-CH(CH_3)- \right)_n$$. It is valued for its high tensile strength and chemical resistance, yet, like PVC, its domain of application lies in fibres, moulded articles, and packaging rather than in protective or decorative coatings.

From the above discussion we see that only glyptal possesses the combination of film-forming ability, gloss, and durability specifically demanded by paints and lacquers.

Hence, the correct answer is Option C.