Q.Vulcanisation of rubber makes it

Match each polymer to its monomer: Phenol-Formaldehyde resin -> Novolac; Neoprene -> Chloroprene; Natural rubber -> Isoprene; Nylon-6 -> Caprolactam. Correct option (a).

Monomer/repeat-unit basis of each:

• (i) P-F (phenol-formaldehyde) resin: the linear low-molecular product is Novolac -> (d).
• (ii) Neoprene: polymer of chloroprene (2-chloro-1,3-butadiene) -> (a).
• (iii) Natural rubber: cis-1,4-polyisoprene, monomer isoprene (2-methyl-1,3-butadiene) -> (b). …

Vulcanisation cross-links the polymer chains of rubber with sulphur, converting the soft, sticky natural rubber into a harder, more durable material.

Natural rubber (cis-1,4-polyisoprene) on its own is soft, tacky, and has poor mechanical strength, with only weak van der Waals forces holding its long polymer chains together, so it becomes soft and sticky in heat and brittle in cold. Vulcanisation is the process of heating raw rubber with sulphur (and often accelerators), which introduces sulphur cross-links (disulphide/polysulphide bridges) between adjacent polyisoprene chains at their double-bond positions.

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Raw natural rubber is soft, sticky, and weak; vulcanisation fixes this by chemically cross-linking its long polyisoprene chains with sulphur bridges.

Raw (unvulcanised) natural rubber is soft, tacky, has poor tensile strength, and its properties change drastically with temperature (becomes sticky when hot, brittle when cold) — making it unsuitable for most practical uses on its own.

Vulcanisation is the process of heating raw rubber with sulphur (and small amounts of additives) at 373–415 K. This forms SULPHUR CROSS-LINKS between adjacent polyisoprene polymer chains, converting the loose network of individual chains into a rigid, interconnected 3D structure.

Purpose/benefits:

• Greatly increases tensile strength and elasticity.
• Removes the sticky/tacky texture. …

Vulcanisation adds sulphur cross-links between rubber's polyisoprene chains, converting soft, tacky raw rubber into a strong, elastic material.

Natural rubber (cis-polyisoprene) is soft, sticky and has poor mechanical strength on its own. When heated with sulphur (typically 3-5%, with accelerators like zinc oxide), sulphur atoms form cross-links (mono-, di-, or polysulphide bridges) between adjacent polymer chains at their residual double bon …