Question 1

Acrylic fibre composition: the major polymer component used to produce acrylic fibres is which of the following?

Accepted Answer

Introduction / Context: Acrylic fibres are ubiquitous in textiles, outdoor fabrics, and carbon-fibre precursors. The base polymer dictates dyeability, thermal behavior, and conversion pathways (e.g., stabilization to form carbon fibre). Given Data / Assumptions: We consider common ISO/ASTM definitions of “acrylic fibre.” Comonomers may be present, but the principal component is decisive. Concept / Approach: Acrylic fibres are predominantly polyacrylonitrile (PAN) or copolymers with high acrylonitrile content. Polyamides (nylons), polyolefins (PE/PP), and polyesters (PET) define other fibre families. Therefore, PAN is the defining major component of acrylic fibres. Step-by-Step Solution: Identify industry definition: “acrylic” → PAN-rich composition.Select PAN as the correct choice.Eliminate other polymer families. Verification / Alternative check: Textile standards specify minimum acrylonitrile content for labelling fibres as “acrylic,” confirming PAN as the major constituent. Why Other Options Are Wrong: Polyamides, polyolefins, polyesters correspond to nylon, olefin, and polyester fibres—not acrylics. Common Pitfalls: Assuming “acrylic” indicates any polymer made from acrylic monomers; fibre labelling is specific to AN content. Final Answer: Polyacrylonitrile (PAN)

Question 2

Tyre manufacturing: which forming/curing method is classically used to produce pneumatic tyres after green-tyre building?

Accepted Answer

Introduction / Context: Tyre production involves compounding, calendaring, bead and ply preparation, green-tyre building, and finally moulding/vulcanisation. The final shaping and curing step defines tread pattern and mechanical performance. Given Data / Assumptions: We refer to conventional pneumatic tyre manufacture. “Green” tyres (uncured assemblies) are placed in a heated mould and cured under pressure. Concept / Approach: The curing step is typically done in a press (or curing bladder) that compresses the green tyre against a mould while heat induces sulphur vulcanisation. This is essentially compression moulding/press vulcanisation. Injection moulding and rotational moulding are used for some thermoplastics or special elastomeric parts, not standard tyre curing. Extrusion forms treads/sidewalls as semi-finished profiles, not complete tyres. Step-by-Step Solution: Identify the final curing/shaping step for tyres.Match it to compression moulding in heated presses with bladders.Eliminate other processes that do not apply to complete tyres. Verification / Alternative check: Tyre plant process diagrams show press curing with moulds/bladders as the defining step. Why Other Options Are Wrong: Injection/rotational moulding: not used for typical tyre production.Extrusion: preforms only; not final tyre. Common Pitfalls: Equating extrusion of tread profiles with the entire tyre manufacturing method. Final Answer: Compression moulding (press vulcanisation)

Question 3

Producing paper-like thin plastic articles (e.g., trays, cups, shells): which forming process is typically used on heated thermoplastic sheets?

Accepted Answer

Introduction / Context: Thin-wall, paper-like plastic articles such as disposable trays, clam shells, and cups are produced by shaping heated sheets over moulds. Selecting the right process is key for economics and wall-thickness control. Given Data / Assumptions: Articles are thin, shallow, and made from sheets (PS, PET, PVC, PP, etc.). High production rates and low tooling cost are desirable. Concept / Approach: Vacuum thermoforming heats a thermoplastic sheet to its softening range and draws it onto a mould using vacuum. It is ideal for producing large numbers of thin, lightweight parts with modest draw ratios. Blow moulding forms hollow bottles from parisons, not shallow sheet parts. Injection moulding fills closed moulds with melt—excellent for complex 3D parts but less economical for broad, thin shells when sheet stock is practical. Step-by-Step Solution: Identify geometry: thin, open, tray-like.Match to sheet-based process: vacuum thermoforming.Exclude blow and injection moulding due to mismatched part geometry and economics. Verification / Alternative check: Packaging lines for cups and trays predominantly use thermoforming machines fed with extruded sheets. Why Other Options Are Wrong: Blow moulding: for hollow containers.Injection moulding: viable but often less efficient for broad, thin shells vs thermoforming. Common Pitfalls: Assuming all high-volume thin parts are injection moulded; sheet forming dominates for trays and cups. Final Answer: Vacuum thermoforming

Question 4

Applications of phenolic thermosets: non-sulphonated hard bakelites are generally NOT used for which of the following products?

Accepted Answer

Introduction / Context: Bakelite is the common name for phenol–formaldehyde thermoset resins. Non-sulphonated, hard grades are valued for heat resistance, dimensional stability, and electrical insulation. However, ion-exchange resins require specific functional groups to perform reversible ion substitution in water-treatment applications. Given Data / Assumptions: Non-sulphonated phenolic (hard bakelite) has no ion-exchange functional groups. Typical bakelite uses: electrical components, handles, knobs, combs, and decorative laminates. Ion-exchange resins must carry acidic or basic ionisable groups (e.g., sulfonic or amine groups). Concept / Approach: Ion-exchange relies on fixed charged sites attached to an insoluble matrix. Non-sulphonated phenolic networks are neutral and lack sulfonic (–SO3H) or quaternary ammonium sites. Therefore, they are unsuitable as ion exchange media without chemical modification. In contrast, moulded goods and laminates benefit from bakelite’s hardness and heat resistance. Step-by-Step Solution: Identify the application that mandates ionic functional groups: ion-exchange resins.Match material chemistry: non-sulphonated phenolic lacks such groups.Conclude: it is not used for ion-exchange resins, whereas it is common for moulded articles and laminates. Verification / Alternative check: Commercial ion-exchange resins are typically sulfonated polystyrene–divinylbenzene (strong acid), phenolic resins only after sulfonation (specialty), or amine-functional resins (anion exchangers). Why Other Options Are Wrong: Fountain pen barrels, formica-type tops, and combs: common uses of hard phenolic thermosets. Common Pitfalls: Assuming any thermoset works for ion exchange; overlooking the essential role of functional groups. Final Answer: Ion-exchange resins

Question 5

Vinyl chloride feedstock: thermal pyrolysis (cracking) of ethylene dichloride primarily produces which compound?

Accepted Answer

Introduction / Context: Vinyl chloride monomer (VCM) is the key feedstock for manufacturing PVC. One major industrial route is the cracking (thermal pyrolysis) of ethylene dichloride (EDC, 1,2-dichloroethane). Given Data / Assumptions: Process: high-temperature EDC cracking. Target product: VCM. By-products include HCl that can be recycled. Concept / Approach: The dehydrochlorination reaction of EDC yields vinyl chloride and hydrogen chloride. The simplified stoichiometry is: 1,2-dichloroethane → vinyl chloride + HCl. This is performed in fired cracking furnaces, followed by rapid quench and product recovery. Step-by-Step Solution: Recognise EDC as the direct precursor to VCM via thermal cracking.Identify primary product pair: VCM and HCl.Choose vinyl chloride as the correct answer. Verification / Alternative check: Alternative routes (e.g., oxychlorination of ethylene to EDC) integrate with EDC cracking in balanced PVC complexes. Why Other Options Are Wrong: Trichloroethylene and ethylene oxide arise from different chemistries.Ethanolamine forms from ethylene oxide and ammonia, not from EDC pyrolysis. Common Pitfalls: Confusing chlorinated solvent production routes with vinyl chloride monomer manufacture. Final Answer: Vinyl chloride

Question 6

Fibre-forming polymers: pick the set in which all listed polymers are suitable for making fibres.

Accepted Answer

Introduction / Context: Fibre formation requires polymers with adequate molecular weight, chain regularity, and ability to be spun (melt, solution, wet, or dry) into filaments that can be drawn and crystallised or oriented. Given Data / Assumptions: Cellulose derivatives (e.g., cellulose acetate, rayon family) are classic fibre polymers. Polyamides (nylons) are archetypal synthetic fibres. Polyurethanes include elastomeric fibre types (e.g., spandex). Concept / Approach: Among the sets, only one contains three polymer families widely used for fibres. Butadiene rubbers and urea–aldehyde resins are not typical fibre materials. Polyisoprene is a rubber; while polyethylene can form fibres, its grouping with polyisoprene makes the set invalid. Silicon is not a thermoplastic polymer; PVC can be solution-spun in niche cases, but the set with silicon fails entirely. Step-by-Step Solution: Screen each set for any member that is not fibre-forming.Reject sets containing rubbers or thermoset resins when asked for fibre use.Select the set comprising cellulose derivatives, polyamides, and polyurethane. Verification / Alternative check: Commercial fibres: cellulose acetate, nylon-6/66, and spandex (PU) are well-established. Why Other Options Are Wrong: (a) Urea–aldehyde is a thermoset; butadiene copolymers are rubbers.(b) Polyisoprene is rubber; set invalid.(d) Silicon is not a fibre-forming thermoplastic polymer; set invalid. Common Pitfalls: Assuming any high-molecular-weight material can be spun; overlooking the need for drawability and structural orientation. Final Answer: Cellulose derivatives, Polyamides, Polyurethane

Question 7

Thermosets versus thermoplastics: which statement correctly characterises thermosetting polymers?

Accepted Answer

Introduction / Context: Thermosetting polymers and thermoplastics differ in processing and final network architecture, which determines recyclability, heat resistance, and solvent response. Given Data / Assumptions: Thermosets cure into infusible networks. Thermoplastics soften on heating and can be remoulded. Polymerisation mechanisms may be step-growth (condensation) or chain-growth (addition) depending on the system. Concept / Approach: The defining feature of a thermoset is its three-dimensional crosslinked network formed during cure. This network prevents flow upon reheating and affords high heat and chemical resistance. In contrast, thermoplastics are typically linear or lightly branched and can be reprocessed. Step-by-Step Solution: Identify the structural hallmark of thermosets: crosslinking into a 3D network.Eliminate statements describing linear, melt-reprocessable behaviour.Select the option that states the crosslinked 3D structure. Verification / Alternative check: Examples: epoxies, phenolics, and melamines are thermosets; polyethylene and polypropylene are thermoplastics. Why Other Options Are Wrong: (a) Some thermosets are not formed by addition; many cure via step-growth.(c) Describes thermoplastics, not thermosets.(d) Incorrect because (b) is correct. Common Pitfalls: Confusing polymerisation mechanism with final network structure; assuming all crosslinked materials are made by addition. Final Answer: They possess a three-dimensional crosslinked structure after cure.

Question 8

Unbreakable crockery and dinnerware: which polymer system is commonly used?

Accepted Answer

Introduction / Context: “Unbreakable” crockery typically refers to hard, glossy, heat-resistant dinnerware that resists staining and maintains shape at serving temperatures. This points to thermoset networks rather than ordinary thermoplastics. Given Data / Assumptions: Desirable traits: hardness, heat resistance, scratch resistance, low porosity. Melamine–formaldehyde (MF) resins form highly crosslinked, durable surfaces. Thermoplastics may soften or deform under heat. Concept / Approach: MF resins cure to glassy, crosslinked networks with excellent surface hardness and sanitary properties, making them ideal for tableware and laminates. The term “unbreakable” is colloquial; MF is still breakable, but far more durable than many thermoplastics in service. Step-by-Step Solution: Match property requirements with resin families.Recognise melamine–formaldehyde as the standard dinnerware resin.Select the MF option. Verification / Alternative check: Commercial products and standards list MF dinnerware due to heat resistance and ease of cleaning. Why Other Options Are Wrong: Generic “thermoplastic” and “addition polymers” are too broad and often lack the heat resistance and hardness required.“None of these” contradicts established practice. Common Pitfalls: Confusing MF with urea–formaldehyde; the latter is less moisture-resistant and not preferred for dinnerware. Final Answer: Melamine (melamine–formaldehyde thermoset)

Question 9

Typical molecular-weight range of commercial plastics: which range is most representative?

Accepted Answer

Introduction / Context: Engineering thermoplastics achieve useful mechanical properties only when the number-average or weight-average molecular weight is sufficiently high to entangle chains and distribute loads. Understanding order-of-magnitude ranges is vital in polymer processing and property prediction. Given Data / Assumptions: Commodity plastics often exhibit Mn or Mw from roughly 2e4 up to 1e6 depending on polymer and grade. Very low molecular weights behave like waxes or oligomers. Extremely high values (10^9+) are unrealistic for linear chains due to processing limits. Concept / Approach: A representative lower bound for practical plastics is around 2e4, where tensile strength and melt elasticity become useful. While many grades exceed 2.5e4, the option closest to a reasonable, representative range among the choices given is 20,000 to 25,000. Step-by-Step Solution: Eliminate impossible or nonsensical ranges (5,000 to 1,000; 10^9 to 10^11).Recognise 1,000 to 5,000 as too low for most plastics (oligomeric).Choose 20,000 to 25,000 as the most representative option provided. Verification / Alternative check: Datasheets often quote Mw: LDPE 1e5–5e5; PP 1e5–7e5; PVC 6e4–1.2e5. The selected option captures a plausible minimum threshold. Why Other Options Are Wrong: Too low or physically unrealistic for processable plastics. Common Pitfalls: Confusing degree of polymerisation with molecular weight; not distinguishing Mn vs Mw. Final Answer: 20,000 to 25,000

Question 10

Trade name identification: a copolymer of vinyl chloride and vinylidene chloride is commonly called what?

Accepted Answer

Introduction / Context: Trade names historically map to specific polymer chemistries. Correct identification is useful for materials selection and legacy documentation. Given Data / Assumptions: Saran refers to vinylidene chloride-based copolymers (often with vinyl chloride). Dacron/terylene are PET polyesters. Orlon is an acrylic fibre (polyacrylonitrile-based). Concept / Approach: Vinylidene chloride imparts excellent barrier properties to oxygen and moisture. Copolymerising with vinyl chloride improves processability; such materials were marketed as “Saran.” Step-by-Step Solution: Map polymer composition to established trade names.Select “Saran” for vinyl/vinylidene chloride copolymers. Verification / Alternative check: Packaging films with high barrier performance historically used Saran coatings. Why Other Options Are Wrong: Dacron/Terylene: PET polyester; Orlon: acrylic—different chemistries and properties. Common Pitfalls: Mixing up legacy trade names with generic polymer families. Final Answer: Saran

Question 11

Polymer fibre spinning methods: dry spinning is typically used for which fibres among the following?

Accepted Answer

Introduction / Context: Fibre spinning methods include melt, wet, and dry spinning. The choice depends on polymer thermal stability and solubility. In dry spinning, a polymer solution is extruded into a chamber of warm gas; the solvent evaporates, leaving solid filaments. Given Data / Assumptions: Polymers that decompose before melting or that dissolve in volatile solvents suit dry spinning. Rayon (viscose) is classically wet-spun (coagulated in a bath). Polyethylene is melt-spun. Concept / Approach: PVC can be formed into fibres by dry spinning from suitable solvents because it cannot be conventionally melt-spun due to thermal degradation near its processing window. Rayon (viscose) uses a coagulation bath (wet spinning), not dry spinning. PVAc may be solution-spun in niche conditions, but PVC is the textbook answer. Step-by-Step Solution: Eliminate melt-spinnable polyethylene.Eliminate viscose rayon (wet-spinning/coagulation route).Select PVC as the standard dry-spinning example. Verification / Alternative check: Process descriptions for acrylics, acetates, and PVC often include dry spinning; viscose relies on wet coagulation chemistry. Why Other Options Are Wrong: Polyethylene is melt-spun; rayon is wet-spun; PVAc is less common as a fibre and not the canonical example. Common Pitfalls: Assuming all solution-spun fibres are dry-spun; confusing dry with wet coagulation steps. Final Answer: Poly(vinyl chloride) (PVC)

Question 12

Free-radical initiation in polymer manufacture: benzoyl peroxide is commonly used as an initiator for which of the following—and notably NOT for which one?

Accepted Answer

Introduction / Context: Benzoyl peroxide (BPO) is a classic free-radical initiator for chain-growth polymerisations such as styrene, vinyl acetate, and related vinyl monomers. Polypropylene, however, is manufactured via coordination catalysis (e.g., Ziegler–Natta or metallocenes), not via BPO-initiated free radicals. Given Data / Assumptions: BPO decomposes thermally to produce radicals that initiate vinyl polymerisation. Vinyl monomers such as styrene, vinyl acetate, and vinyl chloride copolymers are amenable to radical routes. Propylene polymerisation uses coordination catalysts to control stereoregularity and high activity. Concept / Approach: Match initiator type to polymerisation mechanism. Radical initiation suits vinyl addition polymerisations with head-to-tail growth. Propylene requires specific active sites for isotactic/syndiotactic control, incompatible with simple radical initiation for commodity PP. Step-by-Step Solution: Identify polymers typically made by free-radical routes (PS, PVAc, VC/VAc).Exclude polypropylene, produced by coordination catalysis.Therefore, BPO is not used for polypropylene manufacture. Verification / Alternative check: Industrial PP plants employ Ziegler–Natta/metallocene catalysts in slurry, bulk, or gas-phase processes. Why Other Options Are Wrong: PS, PVAc, and VC/VAc copolymers are standard free-radical systems where BPO or AIBN are common initiators. Common Pitfalls: Confusing “benzoyl chloride” with “benzoyl peroxide.” The active initiator is benzoyl peroxide. Final Answer: Polypropylene

Question 13

Polyethylene (polythene) classification: which statement best describes its mode of formation?

Accepted Answer

Introduction / Context: Polyethylene (PE) is the world’s most produced plastic, encompassing LDPE, LLDPE, and HDPE grades. Its manufacture pathway defines key molecular features such as branching and crystallinity. Given Data / Assumptions: Monomer: ethylene (CH2=CH2). Mechanism: chain-growth addition polymerisation. Catalysts: free-radical (LDPE) or coordination (Ziegler–Natta/metallocene for HDPE/LLDPE). Concept / Approach: Addition polymerisation adds monomer units without elimination of small molecules, growing chains via active centres (radicals, ions, or coordination sites). PE is not a condensation product and is a thermoplastic, not a thermoset. Step-by-Step Solution: Recognise ethylene → polyethylene via addition.Eliminate condensation and thermoset options.Select “Addition polymerisation product.” Verification / Alternative check: Process routes (high-pressure radical LDPE, slurry/gas-phase ZN for HDPE) all rely on addition chemistry. Why Other Options Are Wrong: Condensation involves by-product elimination; thermosets crosslink irreversibly—neither describes PE. Common Pitfalls: Confusing polymerisation mechanism with thermal behaviour; PE is thermoplastic and addition-formed. Final Answer: Addition polymerisation product

Question 14

Identify Teflon: which description correctly names this widely used fluoropolymer?

Accepted Answer

Introduction / Context: Teflon is a well-known trade name for a fluorinated polymer famous for its low surface energy, chemical inertness, and high temperature resistance. Given Data / Assumptions: Teflon corresponds to PTFE. PTFE is an organic polymer consisting of carbon–carbon backbone fully fluorinated. Applications include non-stick coatings, seals, and chemical service linings. Concept / Approach: PTFE’s repeat unit is –CF2–CF2– obtained by addition polymerisation of tetrafluoroethylene. It is not a phenolic resin, not an inorganic polymer, and certainly not a monomer. Step-by-Step Solution: Map Teflon → PTFE.Eliminate incorrect classes.Select PTFE. Verification / Alternative check: Material datasheets and standards list PTFE under fluoropolymers with extremely low friction coefficients. Why Other Options Are Wrong: Phenolic resin is a different thermoset; “inorganic polymer” does not fit carbon-based PTFE; a monomer is a single small molecule, not Teflon. Common Pitfalls: Confusing PTFE with PFA or FEP; all are fluoropolymers but have distinct processing windows. Final Answer: Polytetrafluoroethylene (PTFE)

Question 15

Polycaprolactam identification: this polymer is more commonly known by which nylon designation?

Accepted Answer

Introduction / Context: Nylon naming can be based on carbon counts of monomers or on a ring-opening process. Polycaprolactam derives from the ring-opening polymerisation of caprolactam (six-membered ring). Given Data / Assumptions: Caprolactam → polycaprolactam → nylon-6. Nylon-66 requires a diamine and a diacid (HMDA + adipic acid). Concept / Approach: Nylon-6 has repeating amide linkages formed by ring-opening of a single monomer, distinct from the two-monomer condensation of nylon-66. Step-by-Step Solution: Recognise polycaprolactam's origin.Map to common designation: nylon-6. Verification / Alternative check: Standards and datasheets use nylon-6 interchangeably with polycaprolactam. Why Other Options Are Wrong: Nylon-66 and PTFE/Teflon and SBR are different polymers. Common Pitfalls: Confusing nylon-6 and nylon-66 due to similar numbering. Final Answer: Nylon-6

Question 16

Monomer of natural rubber: which compound polymerises to form natural rubber?

Accepted Answer

Introduction / Context: Natural rubber is a polyterpene formed in plants via enzymatic polymerisation. Identifying its monomer clarifies its structure and properties. Given Data / Assumptions: Natural rubber is cis-1,4-polyisoprene. Isoprene = 2-methyl-1,3-butadiene. Butyl rubber, by contrast, is based on isobutylene copolymerised with isoprene in small amounts. Concept / Approach: The repeating unit in natural rubber arises from isoprene via 1,4-addition polymerisation, yielding an unsaturated backbone responsible for vulcanisation behaviour. Step-by-Step Solution: Identify isoprene as the terpenic monomer.Exclude isobutylene which forms butyl rubber with different properties.Exclude DMT which is a polyester intermediate for PET. Verification / Alternative check: Structural analyses show cis-1,4 double-bond configuration in natural rubber. Why Other Options Are Wrong: DMT relates to PET; isobutylene is not the sole monomer of natural rubber. Common Pitfalls: Confusing isoprene with isobutylene due to similar names. Final Answer: Isoprene

Question 17

Use of phthalic anhydride in polymer/chemical industry: which statement best matches a major application?

Accepted Answer

Introduction / Context: Phthalic anhydride (PA) is an important aromatic anhydride used to make phthalate plasticisers and alkyd resins, among other products. Recognising its core role helps avoid misattribution to unrelated polymers. Given Data / Assumptions: PA + alcohols → phthalates (e.g., DOP/DEHP historically), widely used as plasticisers. PA is not a direct precursor to PVC or nylon-6. PA contributes to alkyd resin synthesis for coatings. Concept / Approach: Plasticisers are low-molecular-weight esters that impart flexibility to PVC and other polymers. PA is esterified with suitable alcohols to produce these plasticisers. PVC itself is produced from vinyl chloride, and nylon-6 from caprolactam, not from PA. Step-by-Step Solution: Match PA's chemistry (aromatic anhydride) with esterification to plasticisers.Eliminate routes unrelated to PA (PVC monomer, nylon-6).Select “As a precursor to plasticisers.” Verification / Alternative check: Coating resin (alkyd) and plasticiser sectors consume large volumes of PA. Why Other Options Are Wrong: PVC and nylon-6 have different precursors; insecticides are not the principal application. Common Pitfalls: Confusing “used in PVC” as plasticiser in PVC compounding versus “used to make PVC.” Final Answer: As a precursor to plasticisers

Question 18

Effects of vulcanisation on rubber: which statement correctly captures a primary effect?

Accepted Answer

Introduction / Context: Vulcanisation introduces crosslinks (commonly sulfur-based) between rubber chains, transforming soft, tacky gum rubber into an elastic, resilient material with improved service properties. Given Data / Assumptions: Crosslink density governs modulus, elasticity, and solvent resistance. Antidegradants are often added to resist ozone and oxidation. Oil and solvent resistance generally improves with appropriate crosslinking and polymer choice. Concept / Approach: Crosslinks restrict chain slippage, enabling elastic recovery and higher tensile strength. They also reduce swelling in oils/solvents by limiting chain mobility. Proper compounding improves ozone/oxygen durability, not the reverse. Step-by-Step Solution: Identify the core transformation: from plastic flow to elastic recovery due to crosslinks.Evaluate property trends: tensile strength increases; solvent/oil resistance typically increases; ozone reactivity decreases with antidegradants.Choose the statement that aligns with these fundamentals. Verification / Alternative check: Stress–strain curves of gum vs vulcanised rubber show higher modulus and recovery post-vulcanisation. Why Other Options Are Wrong: Tensile strength does not decrease; ozone/oxygen reactivity decreases with suitable additives; oil/solvent resistance does not decrease. Common Pitfalls: Assuming any crosslinking reduces flexibility to brittleness—over-vulcanisation can embrittle, but correct cure enhances elasticity. Final Answer: Converts its plasticity into elasticity (improves elastic recovery)

Question 19

Identify the polymer from its monomer: polymerisation of chloroprene yields which synthetic rubber?

Accepted Answer

Introduction / Context: Chloroprene (2-chloro-1,3-butadiene) is a diene monomer used to make a prominent synthetic rubber with good weathering and oil resistance. Given Data / Assumptions: Chloroprene → polychloroprene (trade name: neoprene). Other rubbers have different monomers: butyl rubber from isobutylene with isoprene; thiokol from polysulfide chemistry; polyurethane rubbers from isocyanates and polyols. Concept / Approach: Match monomer to the corresponding commercial polymer family and trade name. Step-by-Step Solution: Identify chloroprene as the precursor of neoprene.Exclude unrelated rubbers based on different monomer families. Verification / Alternative check: Neoprene exhibits notable ozone, oil, and weather resistance due to chlorine in the polymer backbone. Why Other Options Are Wrong: Thiokol, butyl, and polyurethane rubbers originate from different chemistries. Common Pitfalls: Confusing chloroprene with isoprene; the former yields neoprene, not natural rubber. Final Answer: Neoprene

Question 20

Molecular weight of PVC: given a degree of polymerisation (DP) of 800, estimate the polymer molecular weight (use 62.5 g/mol per repeat unit).

Accepted Answer

Introduction / Context: For vinyl polymers such as PVC, an approximate molecular weight can be estimated by multiplying the degree of polymerisation (number of repeat units) by the molar mass of the repeat unit. Given Data / Assumptions: Repeat unit of PVC (–CH2–CHCl–) ≈ 62.5 g/mol. Degree of polymerisation, DP = 800. Neglect end-group contributions. Concept / Approach: M ≈ DP * M_repeat. This linear estimate is commonly used for quick calculations when end groups are negligible relative to the chain mass. Step-by-Step Solution: M_repeat ≈ 62.5 g/mol.M ≈ 800 * 62.5 = 50,000 g/mol.Round to the nearest option: 50,000. Verification / Alternative check: Alternate rounding of atomic weights gives similar values; end-group mass adds negligibly at DP 800. Why Other Options Are Wrong: 51,600; 49,200; 50,800 arise from using different per-unit masses or arithmetic errors. Common Pitfalls: Using monomer mass including vinyl unsaturation instead of the repeat-unit mass; mixing DP with molecular weight distribution metrics (Mn, Mw). Final Answer: 50,000

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