Question 1

Feedstock for caprolactam (nylon-6 precursor): which starting material is commonly used in industry?

Accepted Answer

Introduction / Context:Caprolactam is the monomer for nylon-6. Its industrial synthesis routes typically begin with cyclohexane or related cyclohexanone/cyclohexanol intermediates.Given Data / Assumptions:Cyclohexane is oxidised to cyclohexanone/cyclohexanol (KA oil).Beckmann rearrangement of cyclohexanone oxime yields caprolactam.Other listed chemicals correspond to different polymer chains (e.g., DMT and ethylene glycol → PET; ethylbenzene → styrene).Concept / Approach:Match each option to its downstream polymer. The only one that maps to caprolactam (nylon-6) is cyclohexane via cyclohexanone/oxime chemistry.Step-by-Step Solution:Identify the KA-oil route to cyclohexanone.Apply Beckmann rearrangement to obtain caprolactam.Select cyclohexane as the starting material.Verification / Alternative check:Alternate routes exist (e.g., phenol → cyclohexanone), but the industrial chain still passes through KA-oil and oxime steps.Why Other Options Are Wrong:DMT + ethylene glycol → PET; ethylbenzene → styrene; ethylene glycol alone is unrelated to caprolactam.Common Pitfalls:Confusing nylon-6 and nylon-66 monomer routes.Final Answer:Cyclohexane

Question 2

Which of the following is a copolymer among the listed choices?

Accepted Answer

Introduction / Context:Copolymers contain two or more distinct monomer species in the same chain. Recognising standard copolymer examples is key for property prediction and processing.Given Data / Assumptions:SBR comprises styrene and butadiene comonomers.Neoprene is polychloroprene (homopolymer of chloroprene).PVC is a homopolymer of vinyl chloride.Concept / Approach:Identify the entry explicitly combining two monomers: SBR. The others are homopolymers in their base forms.Step-by-Step Solution:List monomers for each polymer.Select the one with two monomers (SBR).Verification / Alternative check:SBR grades vary in styrene content (e.g., 23–25%), tuning glass transition and properties.Why Other Options Are Wrong:Neoprene and PVC are homopolymers in standard commercial practice.Common Pitfalls:Assuming trade names imply copolymer status; verify monomer list.Final Answer:Styrene–butadiene rubber (SBR)

Question 3

Thermocole (expanded foam) identification: this spongy, porous, rigid or flexible foamed plastic is obtained by foaming which base polymer?

Accepted Answer

Introduction / Context:Thermocole (common name in some regions) refers to expanded polystyrene (EPS), a lightweight cellular plastic used for packaging, insulation, and disposable items.Given Data / Assumptions:EPS is produced by expanding polystyrene beads with blowing agents (e.g., pentane, steam expansion).Polyurethane foams also exist but are not called thermocole.Saturated polyester foams are not the typical material for this application.Concept / Approach:Identify the colloquial term “thermocole” with EPS. The base polymer is polystyrene; expansion creates the cellular structure while the chemistry remains polystyrene.Step-by-Step Solution:Associate “thermocole” with EPS.EPS derives from polystyrene beads → select polystyrene.Verification / Alternative check:Industry practice and packaging standards list thermocole as EPS, not polyurethane.Why Other Options Are Wrong:Polyurethane foams are widely used but are distinct and not termed thermocole; saturated polyester is not the standard base for this product.Common Pitfalls:Equating any foam with thermocole; the term is specifically linked to polystyrene.Final Answer:Polystyrene

Question 4

Polyester formation in polymer chemistry: Polyesters are commonly manufactured by the polycondensation of which types of monomers?

Accepted Answer

Introduction / Context:Polyesters are a cornerstone family of engineering plastics and fibres, produced industrially in massive volumes (e.g., PET for bottles and fibres). Knowing the typical monomer pair used in their synthesis helps students distinguish condensation (step-growth) systems from addition (chain-growth) systems and connects directly to properties such as melting point, crystallinity, and hydrolysis resistance.Given Data / Assumptions:Commercial polyesters (e.g., PET) are formed by step-growth reactions.Polycondensation eliminates a small molecule such as water or methanol.We focus on the typical functional group pairing found in polyesters.Concept / Approach:A polyester repeats the ester linkage along the chain. To build that linkage via condensation, one needs a diacid (or diester) and a diol (dihydric alcohol). During polymerisation, ester bonds form repeatedly while releasing small molecules. This contrasts with vinyl addition polymers that arise from unsaturated monomers without elimination of small molecules. Therefore, the classic answer is the combination of a dibasic acid and a dihydric alcohol.Step-by-Step Solution:Identify the repeating functional group: ester.Recall ester formation chemistry: acid (or acid derivative) + alcohol.Scale to polymer level: choose difunctional monomers for step-growth.Conclude the pair is dibasic acid + dihydric alcohol.Verification / Alternative check:Common production routes confirm this: PET is made from dimethyl terephthalate (or terephthalic acid) and ethylene glycol, producing methanol or water as by-product during polymer growth.Why Other Options Are Wrong:A single monomer: possible only for special self-condensing systems, not the standard route taught for polyesters.Carboxylic acid with ethylene: ethylene is not a diol; no ester network forms.Inorganic acid with ethylene glycol: yields inorganic esters, not typical polyester chains.Dicarbamate with diamine: leads to polyurethanes or polyureas, not polyesters.Common Pitfalls:Confusing PET's “terephthalate” name with vinyl addition; it is a condensation product of diacid (or diester) and diol.Final Answer:Dibasic acid with dihydric alcohol

Question 5

Polymethyl methacrylate (PMMA), also called Perspex or acrylic glass, is produced by bulk polymerisation of methyl methacrylate. PMMA is not a/an ______ polymer. Select the most accurate completion.

Accepted Answer

Introduction / Context:PMMA (acrylic glass) is widely used for glazing, lenses, and transparent housings because of its clarity and weatherability. Understanding whether PMMA behaves as a thermoplastic or thermoset informs processing options (injection molding, extrusion, thermoforming) and recyclability.Given Data / Assumptions:Methyl methacrylate undergoes chain-growth (addition) polymerisation to PMMA.PMMA exhibits glass-like transparency and is moldable.Thermoplastics can be reheated and reshaped below their degradation temperature.Concept / Approach:PMMA is a linear (though possibly lightly branched) addition polymer. It softens upon heating and can be remolded, which is characteristic of thermoplastics, not thermosets. Thermosets form infusible, three-dimensional networks that do not melt. Therefore, the statement correctly completed is that PMMA is not a thermosetting polymer.Step-by-Step Solution:Classify PMMA: an addition polymer of MMA.Recall that PMMA can be melted and processed repeatedly (within limits).Thermosets cannot melt; PMMA does.Hence it is not thermosetting.Verification / Alternative check:Processing guides show PMMA being injection molded and thermoformed, which are thermoplastic processes.Why Other Options Are Wrong:Thermoplastic/linear/glass-like transparent/amorphous optical-grade: all describe PMMA accurately.Common Pitfalls:Confusing “glassy” appearance with “thermoset”; glassy refers to the amorphous state above brittleness, not network chemistry.Final Answer:Thermosetting

Question 6

Thermal property check: the approximate softening point of high-density polyethylene (HDPE) is closest to which temperature (°C)?

Accepted Answer

Introduction / Context:HDPE is a semicrystalline thermoplastic used in pipes, containers, and geomembranes. A quick mental map of its softening/melting range is essential for material selection and processing limits like hot-fill, sterilisation, and service temperature envelopes.Given Data / Assumptions:HDPE has higher crystallinity than LDPE, raising its melting/softening range.Typical DSC melting peaks for HDPE occur around 130–135 °C, formulation dependent.Concept / Approach:The Vicat softening temperature and melting peak of HDPE concentrate near the mid-130 °C region. While exact values vary with molecular weight and branching, 135 °C is widely accepted as a representative softening point for quick-reference MCQs.Step-by-Step Solution:Recall HDPE melts higher than LDPE due to crystallinity.Match common practice figure: about 135 °C.Choose 135 °C as the closest option.Verification / Alternative check:Manufacturer datasheets often quote melting temperatures near 130–135 °C and Vicat softening in a similar ballpark, confirming the selection.Why Other Options Are Wrong:85/115 °C: more typical of LDPE or soft thermoplastics.165/205 °C: exceed HDPE melt; closer to PP or nylons.Common Pitfalls:Confusing softening (Vicat) with glass transition; HDPE has very low Tg (around -120 °C).Final Answer:135

Question 7

Manufacturing of collapsible toothpaste tubes: Which extrusion process is commonly used to produce thin-walled, seamless collapsible tubes (e.g., for toothpaste)?

Accepted Answer

Introduction / Context:Collapsible tubes for toothpaste, ointments, and creams are traditionally made from soft metals (e.g., aluminum) by an extrusion process that forms seamless, thin-walled shells. Identifying the specific extrusion style helps distinguish bulk metal-shaping methods used for containers versus those for bars, rods, or profiles.Given Data / Assumptions:Tubes are thin-walled, seamless, and closed at one end after heading.Material is a ductile, low-strength metal slug (often Al alloy).High-speed production requires cold forming.Concept / Approach:Impact extrusion is a cold extrusion process in which a punch strikes a metal slug at high speed, forcing material to flow backward around the punch and up the die walls. This produces seamless, uniform tubes suitable for collapsible packaging. Direct and indirect extrusion are continuous/profile-forming operations, not optimal for thin, closed-end tube shells; hydrostatic extrusion targets difficult-to-deform materials in continuous forms, not discrete tubes.Step-by-Step Solution:Match product (thin, seamless tube) to forming route.Recognise backward flow around the punch in impact extrusion.Note capacity for high production rates and good surface finish.Select impact extrusion.Verification / Alternative check:Packaging manufacturing references consistently cite impact (backward) extrusion for aluminum toothpaste tubes and aerosol can bodies (with variations).Why Other Options Are Wrong:Direct/indirect extrusion: suitable for long profiles or hollow sections with mandrels, not collapsible tubes from slugs.Hydrostatic extrusion: a niche method for continuous forms, not discrete collapsible tubes.Common Pitfalls:Confusing deep drawing (for cups/cans) with impact extrusion; toothpaste tubes are typically produced by impact extrusion of metal slugs.Final Answer:Impact extrusion

Question 8

Rayon classification in fibre science: Rayon is best described as which type of fibre?

Accepted Answer

Introduction / Context:Textile fibres are grouped by origin and chemistry: natural, regenerated, and fully synthetic. Rayon is often misunderstood because it is derived from cellulose yet manufactured by a chemical process. Recognising where rayon fits is essential for predicting properties like moisture regain, dyeability, and thermal behavior.Given Data / Assumptions:Rayon originates from natural cellulose (e.g., wood pulp).Rayon is manufactured via regeneration processes (viscose or cuprammonium routes).“Natural fibres” usually refer to directly harvested fibres like cotton, silk, wool.Concept / Approach:Rayon is a regenerated cellulosic fibre. The cellulose is dissolved chemically and reprecipitated as continuous filaments. It remains cellulosic in chemistry (glucose repeat units) but is not “natural” in the strict fibre classification because it is manufactured from solution rather than harvested as a fibre. Hence, the most accurate classification is “cellulosic.”Step-by-Step Solution:Identify chemistry: cellulose backbone.Identify process: dissolve and regenerate (manufactured fibre).Conclude category: regenerated cellulosic.Select “Cellulosic.”Verification / Alternative check:Standards (e.g., textile fibre generic names) place rayon in the regenerated cellulose family alongside modal and lyocell variants.Why Other Options Are Wrong:Polyamide/polyester: synthetic families (nylon/PET), not rayon.Natural: rayon is man-made from natural polymer; it is not a natural fibre in classification.Inorganic glass fibre: unrelated chemistry and properties.Common Pitfalls:Equating “from plants” with “natural fibre”; processing route matters for classification.Final Answer:Cellulosic

Question 9

Nylon 6,10 used for bristles has lower water absorption than nylon 6,6. Nylon 6,10 belongs to which polymer family?

Accepted Answer

Introduction / Context:Nylons are designated by numbers indicating the carbon count of monomer units. Performance differences, such as water absorption and stiffness, depend on chain structure and amide group density. Nylon 6,10 is well known for bristles because it absorbs less water than nylon 6,6, maintaining stiffness in wet service (e.g., toothbrushes and industrial brushes).Given Data / Assumptions:Nylon 6,10 forms from hexamethylene diamine (6 carbons) and sebacic (decanedioic) acid (10 carbons).Amide linkage density affects moisture uptake.Concept / Approach:All nylons are polyamides, created by condensation of diamines and diacids (or by ring-opening of lactams). Nylon 6,10 is therefore a polyamide. Its lower amide concentration per unit length compared to nylon 6,6 contributes to lower water absorption, stabilising stiffness and dimensional stability for bristle applications.Step-by-Step Solution:Interpret the nomenclature “6,10” as diamine C6 + diacid C10.Recognise formation of amide linkages (–CONH–).Map to polymer family: polyamide.Select “Polyamide.”Verification / Alternative check:Materials datasheets list nylon 6,10 properties, explicitly classifying it as a polyamide with reduced moisture uptake compared to nylon 6,6.Why Other Options Are Wrong:Polyester/polyisoprene/polystyrene/polyacetal: different backbones and properties.Common Pitfalls:Misreading “6,10” as a copolymer with different families; it is within the nylon (polyamide) family.Final Answer:Polyamide

Question 10

Natural thermoplastic resin from animal origin: identify the only widely recognized natural thermoplastic that is a product of animal life.

Accepted Answer

Introduction / Context:Most thermoplastics are synthetic, but a few natural resins soften upon heating and can be reworked. Distinguishing plant exudates from animal-derived resins is a common exam theme in materials and surface-coatings curricula.Given Data / Assumptions:Shellac is secreted by the lac insect and refined into flakes.Rosin, amber, and copal are plant-derived (exudates or fossil resins).Concept / Approach:Shellac is the only option listed that is produced by an animal (lac insect). In flake form, it can be dissolved in alcohols for coatings and can also soften with heat, so it is treated as a natural thermoplastic resin. The others come from trees or fossilised resin and are not of animal origin.Step-by-Step Solution:Identify the biological source of each resin.Confirm shellac's insect origin and thermoplastic behavior.Select “Shellac.”Verification / Alternative check:Coatings handbooks describe shellac as a natural resin from Kerria lacca, widely used historically in varnishes and food/medical glazing.Why Other Options Are Wrong:Rosin/amber/copal/lacquer gums: plant or fossil resins, not animal products.Common Pitfalls:Assuming all natural resins are plant-derived; shellac is the key exception.Final Answer:Shellac

Question 11

Raincoat materials in polymer engineering: Which material is most commonly used for manufacturing conventional raincoats and rainwear fabrics?

Accepted Answer

Introduction / Context:Rainwear requires water-impermeable yet flexible films or coatings applied to fabrics. Several polymers can provide waterproofing, but market prevalence and cost often determine the mainstream choice for mass rainwear.Given Data / Assumptions:PVC (polyvinyl chloride) is inexpensive and easily plasticised into flexible films/coatings.Other elastomers are used in specialty gear but at higher cost or with different feel.Concept / Approach:Conventional raincoats, ponchos, and low-cost waterproof garments are frequently PVC-coated or PVC-film based, using plasticisers to achieve softness at room temperature. Polyurethane coatings are common in higher-performance rainwear, and neoprene or silicone rubbers appear in specialty applications, but the textbook/MCQ “most common” answer remains PVC for general rainwear.Step-by-Step Solution:Consider balance of cost, processability, and water barrier.PVC with plasticiser provides flexible waterproof films.Select PVC as the mainstream choice.Verification / Alternative check:Textile finishing references and commodity film market data consistently show PVC dominating low-cost rainwear and protective clothing segments.Why Other Options Are Wrong:Neoprene/silicone rubber: used for wetsuits or specialty garments, not the commodity raincoat segment.Polyurethane: widely used but typically cited for performance gear; MCQ convention prefers PVC as the generic answer.SBR: uncommon as a raincoat coating polymer.Common Pitfalls:Assuming “best performance” equals “most common”; cost and manufacturability drive mass usage.Final Answer:PVC

Question 12

Industrial manufacture of styrene–butadiene rubber (SBR): which polymerisation route is most widely used commercially?

Accepted Answer

Introduction / Context:SBR is a workhorse synthetic elastomer used in tyres, footwear, and many rubber goods. The production route strongly affects molecular weight distribution, branching, and microstructure, which in turn govern processing and performance. Identifying the mainstream route is a frequent exam topic in polymer technology.Given Data / Assumptions:Large-scale SBR production aims for controllable particle size and heat removal.Emulsion systems offer good control over kinetics and morphology.Concept / Approach:Commercial SBR is predominantly made by emulsion polymerisation (cold or hot), where monomers are dispersed in water with surfactants and polymerised using free-radical initiators. This process manages exotherms effectively, produces latex amenable to coagulation, and allows tuning of properties. Solution SBR exists for specialty grades (e.g., improved tire performance), but the classical and historically dominant route is emulsion polymerisation.Step-by-Step Solution:Recall historical “hot” and “cold” emulsion SBR processes.Note advantages: heat management, latex handling, broad grade control.Select emulsion polymerisation.Verification / Alternative check:Industry overviews consistently identify emulsion SBR (E-SBR) as the principal commodity process, with solution SBR (S-SBR) filling performance niches.Why Other Options Are Wrong:Bulk/suspension: not standard for SBR; heat and viscosity management are challenging.Solution: important but not the classical mass-production route in exam context.Common Pitfalls:Confusing the growing role of S-SBR in modern tires with the historical “most widely used” process; exams typically expect emulsion.Final Answer:Emulsion polymerisation

Question 13

Polymer basics — identify the wrong statement: Choose the statement that is incorrect regarding polymer classifications and properties.

Accepted Answer

Introduction / Context:This conceptual item checks familiarity with polymer terminology (homopolymer vs. copolymer) and the qualitative ranking of intermolecular forces across major polymer classes (elastomers, thermoplastics, fibres). It also probes understanding of vulcanisation effects on rubber elasticity and resilience.Given Data / Assumptions:Elastomers have the weakest cohesive forces and low glass-transition temperatures.Thermoplastics exhibit intermediate cohesive forces and softening on heating.Fibres (e.g., nylons, aramids) possess highly oriented chains and strong intermolecular forces, often hydrogen bonding.Concept / Approach:Correct qualitative ordering: elastomers (weak) < thermoplastics (intermediate) < fibres (strong). Vulcanisation increases rubber’s elastic recovery and reduces plastic flow compared with the raw gum, so “more elastic” is acceptable in the everyday engineering sense of resilience and shape recovery. The only patently incorrect statement supplied is that thermoplastics “always have stronger intermolecular forces than fibres,” which reverses the accepted order.Step-by-Step Solution:Evaluate definitions: homopolymer and copolymer statements are correct.Check rubber fact: vulcanisation enhances elastic recovery versus uncured natural rubber.Recall force ranking: elastomer < thermoplastic < fibre.Identify the wrong claim: thermoplastics stronger than fibres.Verification / Alternative check:Materials texts place high-performance fibres at the top of the cohesion/modulus scale because of orientation and strong secondary bonding (and, in some cases, crystallinity and hydrogen bonds).Why Other Options Are Wrong:Homopolymer/copolymer definitions are standard.Vulcanised rubber’s improved elastic recovery is a well-known outcome.Thermoplastics intermediate forces: widely accepted qualitative description.Common Pitfalls:Confusing “percent elongation at break” (which may decrease upon curing) with elastic recovery; elasticity here refers to resilience and shape-return capability.Final Answer:Thermoplastics always have stronger intermolecular forces than fibres.

Question 14

Terylene identification: “Terylene” is a trade name used historically in fibres. Which statement best describes it?

Accepted Answer

Introduction / Context:Trade names often map to standard polymer families. Terylene (UK) and Dacron (USA) became synonymous with polyethylene terephthalate (PET) fibres, the dominant polyester fibre in apparel and industrial applications. Recognising these equivalences prevents confusion in technical reading and procurement.Given Data / Assumptions:Terylene and Dacron are historical brand names for PET fibre.PET is a polyester formed by condensation of terephthalic acid (or DMT) with ethylene glycol.Concept / Approach:The accurate description is that Terylene equals Dacron in generic chemistry and both refer to the polyester family. Hence, the correct choice is “Both (a) & (b).”Step-by-Step Solution:Identify brand equivalence (Terylene ↔ Dacron).Confirm polymer family: polyester (PET).Pick combined answer “Both (a) & (b).”Verification / Alternative check:Fibre dictionaries and historical marketing document that Terylene (ICI) and Dacron (DuPont) were PET brands.Why Other Options Are Wrong:Each alone is incomplete; “Neither” is false; polyamide is incorrect.Common Pitfalls:Confusing polyester (PET) with polyamide (nylon) because both can be melt-spun and drawn.Final Answer:Both (a) & (b)

Question 15

Condensation vs. addition polymers: Which of the following is NOT a condensation (step-growth) polymer?

Accepted Answer

Introduction / Context:Polymerisation mechanisms determine processing and properties. Condensation (step-growth) polymers arise from reactions between functional groups with small-molecule elimination; addition (chain-growth) polymers form by opening double bonds without eliminating small molecules. Accurately classifying common materials is a frequent exam task.Given Data / Assumptions:Bakelite: phenol–formaldehyde condensation network.Melamine polymers: melamine–formaldehyde condensation networks.PMMA: addition polymer of methyl methacrylate.Polycarbonate: condensation of bisphenol A and phosgene (or transesterification route).Concept / Approach:Among the options, PMMA is the only clear example of an addition (chain-growth) polymer, not a condensation product. Therefore it is the correct choice for “not a condensation polymer.”Step-by-Step Solution:List each polymer's mechanism.Identify PMMA as chain-growth (vinyl addition).Select PMMA as not condensation.Verification / Alternative check:Polymer science references classify methacrylate polymers as addition products; phenolic, melamine, and polycarbonate systems are step-growth.Why Other Options Are Wrong:Bakelite/melamine/polycarbonate: all produced by condensation/step-growth pathways.Common Pitfalls:Assuming “transparent” implies addition; transparency is an optical property, not a mechanism indicator.Final Answer:Polymethyl methacrylate (PMMA)

Question 16

Phenolic thermoset formation: Condensation polymerisation of which pair of reactants produces Bakelite (phenol–formaldehyde resin)?

Accepted Answer

Introduction / Context:Bakelite is the archetypal thermosetting resin, formed by condensation of phenol with formaldehyde to yield a cross-linked network. Recognising the correct monomer pair distinguishes phenolic resins from other condensation systems like urea–formaldehyde or melamine–formaldehyde.Given Data / Assumptions:Bakelite is the trade name associated historically with phenol–formaldehyde resins.Cross-linking occurs during cure, making the material infusible.Concept / Approach:Phenol reacts with formaldehyde under acidic or basic catalysis to form hydroxymethyl phenols and then methylene/methylene-ether bridges, ultimately creating a 3D network known as Bakelite. Other aldehyde–amine systems produce different thermosets (e.g., urea–formaldehyde), not Bakelite.Step-by-Step Solution:Identify Bakelite as phenolic resin.Recall monomers: phenol + formaldehyde.Select the correct pair.Verification / Alternative check:Materials encyclopedias uniformly define Bakelite as the phenol–formaldehyde thermoset network.Why Other Options Are Wrong:Propylene: forms polypropylene via addition.Phenol & acetaldehyde: not the standard pair for phenolic resins.Urea & formaldehyde: yields UF resins.Common Pitfalls:Confusing UF/MF with phenolics due to similar condensation chemistry; the phenolic monomer identity is key.Final Answer:Phenol & formaldehyde

Question 17

Industrial polypropylene production: Which polymerisation mode is most closely associated with large-scale commercial manufacture of polypropylene?

Accepted Answer

Introduction / Context:Polypropylene (PP) is produced via coordination catalysis (Ziegler–Natta or metallocene). Reactor and process choices (bulk/slurry/gas phase) impact tacticity, molecular weight, and product form. Many exam syllabi cite “bulk” (slurry/loop) processes for PP because the polymer is produced essentially in the liquid monomer or hydrocarbon medium at relatively low pressure compared to radical routes for LDPE.Given Data / Assumptions:Coordination polymerisation yields highly stereoregular PP.Industrial processes include bulk (slurry/loop) and gas-phase reactors.Concept / Approach:“Bulk” is the classical answer in educational contexts, referring to slurry/loop reactors using liquid propylene (and/or diluents) as reaction medium. Emulsion polymerisation is not used for PP; solution processes apply more to other polymers; suspension is not the common PP route. Gas-phase is also widely used in practice, but “bulk” remains the traditional textbook selection for MCQs framed this way.Step-by-Step Solution:Map PP to coordination catalysis at low pressure.Recall loop (bulk/slurry) reactors as canonical.Select “Bulk.”Verification / Alternative check:Process histories from major licensors describe loop slurry (“bulk”) and gas-phase routes; among provided options, bulk is the representative educational answer.Why Other Options Are Wrong:Emulsion/suspension: typical for vinyl chloride, styrene, but not PP.Solution: not the mainstream PP route cited in basic MCQs.Common Pitfalls:Overemphasising gas-phase while ignoring that the question asks for a single “employs” mode; many syllabi emphasise bulk.Final Answer:Bulk

Question 18

Effect of styrene content in SBR: Increasing styrene fraction during SBR copolymerisation adversely affects which property most noticeably?

Accepted Answer

Introduction / Context:SBR properties depend on the styrene-to-butadiene ratio. As styrene content rises, the rubber becomes harder and more plastic-like; dynamic properties such as resilience and low-temperature flexibility deteriorate. Understanding this trade-off guides compound selection for tires and mechanical goods.Given Data / Assumptions:Higher styrene raises glass transition temperature and hardness.Dynamic elastic recovery (resilience) tends to decrease with higher Tg.Concept / Approach:Resilience measures the ability of a rubber to return energy elastically. When styrene content increases, Tg shifts upward, internal friction rises, and resilience decreases. Percent elongation also tends to drop, but resilience is classically highlighted as the adversely affected property in many question banks, because it is central to dynamic service (e.g., rolling resistance and heat buildup).Step-by-Step Solution:Relate styrene content → higher Tg and stiffness.Higher Tg → poorer elastic energy return (lower resilience).Select “Resilience.”Verification / Alternative check:Rubber compounding texts show resilience decreasing with increasing styrene content in SBR grades.Why Other Options Are Wrong:Percent elongation may also reduce, but resilience is the definitive dynamic metric affected.Freezing point is not the standard property discussed here.Strength/abrasion: may vary but not the primary adverse effect attributed to styrene increase.Common Pitfalls:Equating hardness increases with improved dynamic performance; harder does not mean more resilient.Final Answer:Resilience

Question 19

Primary application sector of acrylonitrile: Acrylonitrile is predominantly used in which industry?

Accepted Answer

Introduction / Context:Acrylonitrile (AN) is an important monomer for several major polymers and copolymers. Knowing its main industrial destination helps connect monomer markets to end-use materials such as acrylic fibres and engineering plastics (ABS, SAN, NBR).Given Data / Assumptions:Acrylonitrile is a vinyl monomer with a nitrile group.Large-scale consumption occurs in polymerisation processes.Concept / Approach:The polymer industry is the principal consumer of AN: it is polymerised to polyacrylonitrile (PAN) for acrylic fibres and copolymerised with butadiene and styrene to make ABS plastics. Other listed industries do not use AN as a major feedstock compared with polymer manufacture.Step-by-Step Solution:Identify AN as a polymerisable monomer.Link to major products: PAN, ABS, SAN, NBR.Select “Polymer” industry.Verification / Alternative check:Market reports show the overwhelming share of AN demand comes from acrylic fibres and ABS/SAN resins.Why Other Options Are Wrong:Printing/dyeing/photographic: not primary bulk consumers of AN.Common Pitfalls:Confusing acrylonitrile (monomer) with acetonitrile (solvent) used in HPLC and other labs.Final Answer:Polymer

Question 20

Identify the non-condensation polymer: Among the following, which polymer is NOT formed by condensation (step-growth) polymerisation?

Accepted Answer

Introduction / Context:Classifying polymers by mechanism avoids confusion when predicting properties. Teflon (PTFE) is a classic addition (chain-growth) polymer from tetrafluoroethylene, whereas nylon-66, PET (Dacron), polycarbonate, and phenolic resin are condensation products formed via step-growth reactions involving functional groups and small-molecule elimination or exchange.Given Data / Assumptions:Teflon forms by radical or coordination addition of tetrafluoroethylene.Nylon-66 forms from adipic acid and hexamethylene diamine.Dacron (PET) forms from terephthalate and ethylene glycol.Polycarbonate and phenolic resins are step-growth systems.Concept / Approach:Select the polymer produced without elimination of small molecules (i.e., addition polymer). PTFE meets this criterion. The others are well-known condensation polymers in standard syllabi.Step-by-Step Solution:List mechanisms for each option.Identify PTFE as addition polymer of TFE.Choose Teflon.Verification / Alternative check:Polymer handbooks place PTFE among vinyl addition polymers; the others appear under step-growth families.Why Other Options Are Wrong:Nylon-66/PET/polycarbonate/phenolic: all formed via condensation or transesterification/condensation reactions.Common Pitfalls:Assuming “high-performance” implies condensation; mechanism depends on monomer functionality, not performance level.Final Answer:Teflon

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