(i) How does vulcanisation change the nature of natural rubber? (ii) Write the names of the monomers each of T

Question 34 of 40

Q. (i) How does vulcanisation change the nature of natural rubber?

(ii) Write the names of the monomers each of Terylene and Dacron. [1+1]

West Bengal WbchseWest Bengal HS (WBCHSE) Board 2024Subjective· 2mImportance★★★★★

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Sulfur cross-linking during vulcanisation converts sticky, weak natural rubber into a strong, elastic material usable over a wide temperature range; Terylene and Dacron are both PET, made from ethylene glycol and terephthalic acid.

(i) Effect of vulcanisation on natural rubber:

Natural rubber (cis-1,4-polyisoprene) is soft, sticky, and has low tensile strength — it becomes tacky when hot and brittle when cold. Vulcanisation involves heating raw rubber with sulfur (and small amounts of additives), which forms sulfur cross-links ("bridges") between the polymer chains at the double-bond sites. This:

greatly increases tensile strength and elasticity,
improves resistance to oxidation and abrasion,
reduces surface tackiness, and
allows the rubber to remain useful over a much wider range of temperatures.

(ii) Monomers of Terylene and Dacron: …

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2026Set SEM31 markMCQ
$Q. Match Column-I with Column-II and select the correct option: Column-I:$
(i) P-F Resin,
(ii) Neoprene,
(iii) Natural rubber,
(iv) Nylon-6. Column-II:
(a) Chloroprene,
(b) Isoprene,
(c) Caprolactam,
(d) Novolac
(a) (i)-(d), (ii)-(a), (iii)-(b), (iv)-(c)
(b) (i)-(a), (ii)-(b), (iii)-(c), (iv)-(d)
(c) (i)-(b), (ii)-(c), (iii)-(d), (iv)-(a)
(d) (i)-(c), (ii)-(d), (iii)-(a), (iv)-(b)
›Reveal solutionSolution
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). …
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CBSE 2025Set ANNUAL1 markMCQ
$Q. Vulcanisation of rubber makes it$
(a) soft
(b) hard
(c) less elastic
(d) soluble in water
›Reveal solutionSolution

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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CBSE 2024Set ANNUAL1 mark
$Q. What is the purpose of Vulcanisation of rubber?$
›Reveal solutionSolution
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. …
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CBSE 2023Set ANNUAL1 markMCQ
$Q. The element which is added to raw rubber to improve its physical properties is$
(a) Carbon
(b) Sulphur
(c) Nitrogen
(d) Oxygen
›Reveal solutionSolution

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 …

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Q.(i) How does vulcanisation change the nature of natural rubber?

Concept understanding — Natural Rubber and Vulcanisation

Q.(i) How does vulcanisation change the nature of natural rubber?

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