--- title: "Inorganic polymer; network polymer of sulphur; silicones" subject: "Engineering Chemistry" chapter: 4 key: "semester_2/engineering_chemistry:inorganic-polymer-sulphur" source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/inorganic-polymer-sulphur site: BCT Engineering --- # Inorganic polymer; network polymer of sulphur; silicones Engineering Chemistry · Chapter 4: Engineering Polymers - Asked in: 2073 Magh, 1+3+1 marks - Video: [Inorganic polymers](https://www.youtube.com/watch?v=ram2AublaEM) — Brent Turner - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/inorganic-polymer-sulphur - Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-4 ## Question What is inorganic polymer? Give an account of preparation and application of network polymer of Sulphur in engineering field. Also mention the two uses of silicones. ## Short answer An inorganic polymer has a backbone of atoms other than carbon. Sulphur network polymers: plastic sulphur made by heating S8 rings to chains and quenching; cross-linked sulphur vulcanises rubber for strength. Thiokol polysulphide sealant. Two silicones uses: high-temperature lubricants and electrical insulation. ## Answer #### Inorganic polymer An **inorganic polymer** is a polymer whose backbone is made of atoms other than carbon (e.g. Si–O, P–N, S–N, B–N). Examples: silicones, polyphosphazenes, polythiazyl, plastic sulphur. #### Network polymers of sulphur **Plastic (polymeric) sulphur.** Ordinary rhombic sulphur has S₈ rings. When sulphur is heated above about 160 °C, the rings open and join into long chains (S)ₙ, and the liquid becomes very viscous. If this hot liquid (heated to near its boiling point) is poured into cold water, the chains are frozen as a brown, rubber-like, elastic solid called **plastic sulphur**. It slowly reverts to the S₈ form. S₈ → (heat above 160 °C) → ·S–S–S...S–S· (chain) → quench in water → plastic sulphur **Cross-linked sulphur polymers.** In vulcanisation, a small amount of sulphur forms –S– and –S–S– cross-links between rubber chains, making the rubber harder and stronger (used for tyres). Polysulphide rubber (**Thiokol**) is obtained from ethylene dichloride and sodium polysulphide: n ClCH₂CH₂Cl + n Na₂S₄ → [–CH₂CH₂–S₄–]ₙ + 2n NaCl. **Applications in engineering:** vulcanised rubber for tyres, belts and hoses; polysulphide (Thiokol) sealants, rocket fuel binders and gaskets resistant to oil and solvents; sulphur concrete for chemical-resistant floors and pipes; (SN)ₓ as a conducting polymer. #### Two uses of silicones 1. Lubricants and greases stable over a wide temperature range. 2. Electrical insulation, sealants, water-repellent coatings and medical implants. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is an inorganic polymer? A. A polymer with no atoms except carbon B. A polymer whose backbone is made of atoms other than carbon, such as Si-O or P-N C. A polymer of metals only D. A plastic filled with minerals Answer: B. Backbone atoms are non-carbon, e.g. silicones and polyphosphazenes. (Key point: Definition) 2. What is plastic sulphur? A. S8 rings in solution B. A brown rubber-like solid of sulphur chains formed by quenching hot sulphur in cold water C. SO3 polymer D. A sulphide ore Answer: B. Chains formed above 160 C are frozen by quenching; it slowly reverts to S8. (Key point: Plastic sulphur) 3. What does sulphur do in vulcanisation? A. Breaks rubber chains B. Forms -S-S- cross-links between rubber chains C. Dissolves the rubber D. Colours the rubber Answer: B. Cross-links make rubber harder, as in tyres. (Key point: Vulcanisation) 4. Which is a use of silicones? A. Lubricants stable over wide temperature B. Fertilisers C. Fuel D. Explosives Answer: A. Silicones are used as temperature-stable lubricants, insulation, sealants and implants. (Key point: Silicone uses) ## Related in Engineering Chemistry - [Linear chain polymer; sulphur-based inorganic polymers](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Alinear-polymer-sulphur-inorganic) — Engineering Chemistry, chapter 4 - [Inorganic polymer characteristics; polyphosphazines](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Ainorganic-polymer-polyphosphazines) — Engineering Chemistry, chapter 4 - [Chalcogenide glasses and network polymers of sulphur](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Achalcogenide-glass-polymers) — Engineering Chemistry, chapter 4 - [Cross linked polymer; inorganic polymer; chalcogenide](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Acrosslinked-inorganic-chalcogenide) — Engineering Chemistry, chapter 4 - [Silicones and their uses](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Asilicones-uses) — Engineering Chemistry, chapter 4 - [Types and uses of silicones](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Asilicones-types-uses) — Engineering Chemistry, chapter 4 ## Related in other subjects - [Engineering surveying; two-way principle application](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aengineering-surveying-two-way-angle) — Surveying I, chapter 1 - [Uses of correlation and regression in engineering](https://www.bctengineer.com/question.md?key=semester_5%2Fprobability_and_statistics%3Acorrelation-regression-uses-engineering) — Probability and Statistics, chapter 5