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Engineer Textile practice questions

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Question 1Textile Fibres and Fibre Science

Which natural fibre is classified as a bast (stem) fibre rather than a seed or leaf fibre?

  1. Cotton
  2. Flax Correct answer.
  3. Coir
  4. Sisal

Explanation

Bast fibres are extracted from the phloem of dicotyledonous stems, and flax (linen) is the classic example, with bundles cemented by pectin. Cotton is a seed-hair fibre, sisal is a leaf fibre, and coir comes from the husk of the coconut fruit.

Question 2Textile Fibres and Fibre Science

The unit of linear density used in the tex system is defined as the mass in grams of a fibre bundle or yarn of what length?

  1. 9 000 m
  2. 10 000 m
  3. 1 000 m Correct answer.
  4. 1 m

Explanation

Tex is the mass in grams per 1 000 metres of linear material, so 1 tex equals 1 g/km. The 9 000 m basis belongs to the denier system, and 10 000 m is not a standard textile linear-density basis.

Question 3Textile Fibres and Fibre Science

Cotton fibre strength measured on a single fibre is most strongly influenced by which structural feature?

  1. Diameter of the lumen
  2. Colour of the fibre after ginning
  3. Degree of polymerisation and crystallite orientation in the secondary wall Correct answer.
  4. Presence of the cuticle wax layer

Explanation

Tensile strength depends on cellulose chain length and how well the crystallites are oriented along the fibre axis in the secondary wall. Higher DP and better orientation give greater strength; lumen size and wax affect other properties.

Question 4Textile Fibres and Fibre Science

Which regenerated cellulosic fibre is produced by dissolving cellulose in a solvent system and spinning it without forming a cellulose derivative?

  1. Modal
  2. Viscose
  3. Acetate
  4. Lyocell Correct answer.

Explanation

Lyocell is spun from a solution of cellulose in N-methylmorpholine N-oxide, a direct-dissolution route that avoids derivatisation. Viscose and modal pass through xanthate chemistry, and acetate is a cellulose ester.

Question 5Textile Fibres and Fibre Science

A polyester filament yarn has a linear density of 150 denier. What is its approximate linear density in tex?

  1. 16.7 tex Correct answer.
  2. 135 tex
  3. 13.5 tex
  4. 150 tex

Explanation

Denier is grams per 9 000 m and tex is grams per 1 000 m, so tex equals denier multiplied by 1 000/9 000, or denier divided by 9. Thus 150 denier corresponds to about 16.7 tex.

Question 6Textile Fibres and Fibre Science

In a single-fibre tensile test, the initial slope of the load-extension curve is used to determine which property?

  1. Initial modulus Correct answer.
  2. Breaking tenacity
  3. Work of rupture
  4. Elastic recovery

Explanation

The slope of the linear elastic region of the load-extension curve, normalised for linear density and gauge length, gives the initial modulus. Breaking tenacity comes from the peak load, while work of rupture is the area under the curve.

Question 7Textile Fibres and Fibre Science

Which feature distinguishes wool from other natural fibres at the morphological level?

  1. A ribbon-like cross-section with convolutions
  2. Presence of pectin cementing fibre bundles
  3. Overlapping cuticle scales along the fibre surface Correct answer.
  4. A central lumen running the full length

Explanation

Wool is characterised by an outer layer of overlapping cuticle scales, which cause directional friction and felting shrinkage. The ribbon-like convoluted form belongs to cotton, and pectin is associated with bast fibre bundles.

Question 8Textile Fibres and Fibre Science

Which property of polyester fibre is the main reason it is often blended with cotton in apparel fabrics?

  1. Low melting point for easy heat setting
  2. High moisture regain and breathability
  3. Biodegradability in soil
  4. High tensile strength and good wrinkle recovery Correct answer.

Explanation

Polyester contributes strength, dimensional stability and crease recovery, while cotton supplies absorbency and comfort, so the blend balances the weaknesses of each. Polyester itself has low moisture regain and is not readily biodegradable.

Question 9Textile Fibres and Fibre Science

Moisture regain of a textile fibre is defined as the moisture content expressed as a percentage of which quantity?

  1. The saturated mass of the fibre
  2. The mass of water absorbed at 100 percent relative humidity
  3. The mass of the fibre including moisture
  4. The oven-dry mass of the fibre Correct answer.

Explanation

Moisture regain is the mass of water in the material divided by the oven-dry mass, multiplied by 100. Moisture content uses the total wet mass as the denominator, which is why the two figures differ for the same sample.

Question 10Textile Fibres and Fibre Science

Which spinning method is used to produce viscose rayon filament yarn?

  1. Melt spinning through a spinneret
  2. Gel spinning from a high-concentration solution
  3. Dry spinning in heated air
  4. Wet spinning into a coagulation bath Correct answer.

Explanation

Viscose is extruded into a spin bath containing sulphuric acid and salts, where the xanthate is regenerated and coagulated, which is wet spinning. Melt spinning suits thermoplastic polymers, and dry spinning is used for acetate and acrylics.

Question 11Textile Fibres and Fibre Science

A yarn is described as 30 tex. What does this indicate about its linear density?

  1. It has a mass of 30 grams per 1 000 metres Correct answer.
  2. It contains 30 filaments in the cross-section
  3. It has 30 turns of twist per metre
  4. It has a mass of 30 grams per 9 000 metres

Explanation

Tex is the mass in grams per 1 000 m, so a 30 tex yarn weighs 30 g per kilometre. The 9 000 m basis is denier, while filament count and twist level are separate yarn parameters.

Question 12Textile Fibres and Fibre Science

Which fibre is an aramid characterised by high strength, high modulus and excellent heat resistance?

  1. Polypropylene
  2. Polyacrylonitrile
  3. Polyethylene terephthalate
  4. Poly(p-phenylene terephthalamide) Correct answer.

Explanation

Para-aramid, poly(p-phenylene terephthalamide), has rigid rod-like chains giving very high tenacity and modulus plus thermal stability. The other polymers are commodity fibres with much lower modulus and heat resistance.

Question 13Textile Fibres and Fibre Science

Why does cotton exhibit a higher moisture regain than polyester?

  1. Cotton has a lower molecular weight
  2. Cellulose chains carry many hydroxyl groups that attract water Correct answer.
  3. Cotton has a higher degree of crystallinity
  4. Polyester has a larger lumen

Explanation

The numerous hydroxyl groups on the cellulose chain form hydrogen bonds with water, giving cotton a regain of roughly 7 to 8.5 percent. Polyester is hydrophobic because it lacks such polar groups, and higher crystallinity would actually reduce regain.

Question 14Textile Fibres and Fibre Science

Which test method is commonly used to determine the linear density of a yarn by weighing a known length?

  1. Martindale abrasion test
  2. Stelometer flat-bundle test
  3. Limiting oxygen index test
  4. Skein or wrap-reel mass method Correct answer.

Explanation

A known length is wound on a wrap reel or skein, conditioned, weighed, and the mass converted to tex or count. The Stelometer measures fibre bundle strength, Martindale measures abrasion, and LOI measures flammability.

Question 15Textile Fibres and Fibre Science

Which structural model best describes the arrangement of molecules in a drawn synthetic filament?

  1. Hollow tube of cellulose
  2. Random coil with no molecular orientation
  3. Fringed micelle model with oriented crystalline and amorphous regions Correct answer.
  4. Perfect single crystal with no amorphous content

Explanation

Drawn filaments are described by the fringed micelle or fringed fibril model, in which crystalline and amorphous regions coexist and chains are oriented along the axis. Perfect crystallinity is unattainable in melt-spun fibres, and random coils describe the undrawn state.

Question 16Textile Fibres and Fibre Science

Which fibre property is most directly responsible for the felting shrinkage of wool fabrics during washing?

  1. Low initial modulus of the fibre
  2. Directional friction from the cuticle scales combined with fibre crimp Correct answer.
  3. High moisture regain of the fibre
  4. Presence of disulphide bonds in the cortex

Explanation

The ratchet-like directional friction of the scales, aided by crimp and fibre migration under agitation, causes fibres to migrate and entangle irreversibly, producing felting shrinkage. Moisture regain and disulphide bonds affect other properties but do not create the ratchet effect.

Question 17Textile Fibres and Fibre Science

A fabric is required to resist degradation by ultraviolet light and retain strength outdoors. Which fibre choice is most appropriate?

  1. Regular viscose
  2. Undyed polypropylene
  3. Solution-dyed acrylic Correct answer.
  4. Cotton

Explanation

Acrylic has good inherent resistance to UV degradation, and solution dyeing further improves lightfastness by dispersing pigment throughout the fibre. Polypropylene is notably sensitive to UV unless stabilised, and cellulosic fibres degrade under prolonged sunlight.

Question 18Textile Fibres and Fibre Science

Which term describes the property of a fibre to return to its original length after being stretched and released?

  1. Tenacity
  2. Creep
  3. Elastic recovery Correct answer.
  4. Flexural rigidity

Explanation

Elastic recovery is the extent to which a fibre recovers its original dimensions after deformation is removed, usually expressed as a percentage. Creep is time-dependent extension under sustained load, and tenacity is breaking stress per linear density.

Question 19Textile Fibres and Fibre Science

In a fibre blend, why is it difficult to achieve an intimate blend of fibres with very different linear densities?

  1. The blend components react chemically
  2. Differing mass per unit length causes segregation during opening and carding Correct answer.
  3. The fibres cannot be dyed together
  4. The fibres have identical friction coefficients

Explanation

When component fibres differ greatly in linear density and length, they behave differently in opening, carding and drafting, leading to segregation and uneven distribution. Dyeing compatibility and chemical reaction are separate issues from mechanical blending uniformity.

Question 20Textile Fibres and Fibre Science

Which property of a fibre is measured by the Limiting Oxygen Index test?

  1. Flammability Correct answer.
  2. Abrasion resistance
  3. Moisture regain
  4. Thermal conductivity

Explanation

The Limiting Oxygen Index is the minimum oxygen concentration in a nitrogen-oxygen atmosphere that supports combustion, so it quantifies flammability. Abrasion, regain and conductivity are measured by entirely different methods.

Question 21Textile Fibres and Fibre Science

Which manufacturing route produces a bicomponent fibre with a core-sheath cross-section?

  1. Conventional wet spinning of viscose
  2. Texturising of a flat filament yarn
  3. Melt blowing of thermoplastic polymer
  4. Conjugate spinning through a specially designed spinneret Correct answer.

Explanation

Bicomponent fibres are made by conjugate spinning, in which two polymers are extruded through a spinneret designed to arrange them in a chosen geometry such as core-sheath or side-by-side. Melt blowing, texturising and conventional wet spinning do not create such cross-sectional polymer arrangements.

Question 22Textile Fibres and Fibre Science

Which of the following is a characteristic of silk as a natural protein fibre?

  1. It is extracted from the stem of a plant
  2. It is a regenerated cellulose fibre
  3. It is produced as a continuous filament by the silkworm Correct answer.
  4. It occurs as short staple hairs on a seed

Explanation

Silk is extruded by the silkworm as a continuous filament, which is why it can be reeled directly into yarn. Staple seed hairs describe cotton, stem extraction describes bast fibres, and regenerated cellulose describes viscose.

Question 23Textile Fibres and Fibre Science

Why does increasing the draw ratio of a melt-spun polyester filament generally increase its tenacity?

  1. The degree of polymerisation falls sharply
  2. The fibre diameter increases
  3. The amorphous content becomes dominant
  4. Molecular chains become more oriented along the fibre axis Correct answer.

Explanation

Drawing straightens and aligns the molecular chains, increasing orientation and crystallinity along the axis, which raises tenacity and modulus. Drawing also reduces diameter, and it does not reduce the degree of polymerisation appreciably.

Question 24Textile Fibres and Fibre Science

Which property makes polypropylene suitable for ropes and geotextiles despite its low melting point?

  1. Excellent heat resistance
  2. High density compared with polyester
  3. High moisture regain
  4. High strength-to-weight ratio and resistance to water and chemicals Correct answer.

Explanation

Polypropylene has a low specific gravity of about 0.91, giving a high strength-to-weight ratio, and it is essentially hydrophobic and chemically inert. Its low melting point and poor heat resistance are limitations, not advantages, and its moisture regain is very low.

Question 25Yarn Manufacture and Spinning

In ring spinning, what is the primary function of the traveller running on the ring?

  1. It controls yarn winding tension and packages the yarn onto the bobbin
  2. It inserts twist into the yarn by lagging behind the spindle speed Correct answer.
  3. It drafts the roving into a thinner strand before twisting
  4. It removes short fibres and trash from the fibre stream

Explanation

The traveller is dragged around the ring by the yarn and rotates more slowly than the spindle because of friction and yarn drag. This speed difference is what inserts twist into the yarn between the front drafting rollers and the traveller. Tension and winding are secondary effects regulated by traveller weight.

Question 26Yarn Manufacture and Spinning

Which fibre parameter most directly governs the minimum twist required to give a staple yarn adequate cohesion?

  1. Fibre crimp frequency
  2. Fibre moisture regain
  3. Fibre brightness
  4. Fibre linear density and length Correct answer.

Explanation

Twist cohesion depends on fibre-to-fibre friction, which is governed largely by fibre fineness and length; finer and longer fibres give more contact points and higher migration, so less twist is needed. Brightness, regain and crimp affect processing or handle but not the fundamental twist-cohesion relationship as strongly.

Question 27Yarn Manufacture and Spinning

In the cotton spinning sequence, which machine converts opened and cleaned tufts into a continuous carded sliver?

  1. Draw frame
  2. Carding machine Correct answer.
  3. Speed frame
  4. Comber

Explanation

The carding machine individualises tufts into single fibres, removes neps and short fibre, and condenses the web into a sliver. The draw frame doubles and drafts slivers, the comber removes short fibre from combed slivers, and the speed frame converts sliver to roving.

Question 28Yarn Manufacture and Spinning

A draw frame is set to double eight slivers and apply a draft of 8. What is the resulting sliver linear density relative to the input sliver?

  1. Eight times the input
  2. Unchanged Correct answer.
  3. One-sixty-fourth of the input
  4. One-eighth of the input

Explanation

Doubling eight slivers multiplies linear density by eight, while a draft of eight divides it by eight, so the output equals the input linear density. Doubling improves evenness by averaging irregularities without changing count. The other options confuse the separate effects of doubling and drafting.

Question 29Yarn Manufacture and Spinning

What is the main purpose of combing in the production of fine cotton yarns?

  1. To insert false twist into the sliver
  2. To remove short fibres and neps to improve yarn evenness and strength Correct answer.
  3. To blend two different fibre types uniformly
  4. To increase the linear density of the sliver

Explanation

Combing removes short fibres below a set length and eliminates neps and impurities, producing a smoother, stronger, more even yarn from longer fibres. It reduces rather than increases linear density and does not insert twist. Blending is achieved by other means such as mixing at blowroom or draw frame.

Question 30Yarn Manufacture and Spinning

Which statement best describes the false-twist principle used in rotor spinning?

  1. Twist is inserted only at the winding drum
  2. Twist is created by the opening roller alone
  3. Twist is inserted in the rotor and then partly removed as the yarn leaves, giving a real twisted yarn Correct answer.
  4. Twist is inserted permanently along the whole yarn length by the rotor

Explanation

In rotor spinning the fibre ribbon is twisted inside the rotor, and as the yarn is withdrawn the twist in the peel-off zone is partly undone, but the net result is a genuinely twisted yarn. The opening roller only individualises fibres and does not insert twist. The winding drum merely packages the yarn.

Question 31Yarn Manufacture and Spinning

In ring spinning, increasing the spinning triangle width generally has what effect on yarn quality?

  1. It has no measurable effect on yarn properties
  2. It increases yarn hairiness and reduces strength Correct answer.
  3. It increases yarn elongation without changing hairiness
  4. It reduces yarn hairiness and improves strength

Explanation

A wide spinning triangle leaves more fibres uncontrolled at the edges, so they protrude as hairs and contribute less to yarn strength. Compact spinning narrows the triangle to reduce hairiness and improve strength. Width therefore has a clear negative effect on quality.

Question 32Yarn Manufacture and Spinning

Which drafting system arrangement is typical of the speed frame (roving frame)?

  1. Single-roller beater drafting with a condenser
  2. Three-roller double-apron drafting with a flyer and bobbin Correct answer.
  3. Rotor with opening roller and fibre channel
  4. Perforated drum with suction and a compacting zone

Explanation

The speed frame uses a multi-roller drafting system, commonly a three-roller double-apron arrangement, followed by flyer twisting and winding onto a bobbin. The other descriptions belong to blowroom, rotor spinning and compact spinning respectively, not to roving production.

Question 33Yarn Manufacture and Spinning

A yarn has a metric count of 40. What is its approximate English cotton count (Ne)?

  1. Ne 24 Correct answer.
  2. Ne 100
  3. Ne 68
  4. Ne 40

Explanation

Metric count (Nm) is the number of 1000 m lengths per kilogram, while English cotton count is the number of 840-yard hanks per pound. The conversion is approximately Ne = Nm × 0.5905, so 40 Nm gives about 23.6 Ne, rounded to 24. The other values ignore the length and mass unit conversion.

Question 34Yarn Manufacture and Spinning

Which factor most strongly limits the maximum spindle speed in ring spinning?

  1. Roving bobbin diameter
  2. Traveller friction and yarn tension at the ring Correct answer.
  3. Fibre colour
  4. Sliver moisture content

Explanation

As spindle speed rises, traveller friction generates heat and tension rises, leading to yarn breaks and traveller wear. This friction and tension limit is the main constraint on ring spinning speed. Colour, moisture and bobbin diameter are secondary or irrelevant to the fundamental speed limit.

Question 35Yarn Manufacture and Spinning

What is the role of the opening roller in rotor spinning?

  1. To compact the fibre ribbon before twisting
  2. To individualise fibres from the sliver and remove impurities Correct answer.
  3. To twist the fibre ribbon into yarn
  4. To draw the yarn onto the package

Explanation

The opening roller, rotating at high speed, combs the sliver into individual fibres and throws them into the fibre channel, while trash is ejected through the trash box. Twisting occurs in the rotor, and winding is done by the take-up drum. Compaction is not part of rotor spinning.

Question 36Yarn Manufacture and Spinning

In woollen spinning, which characteristic distinguishes the process from worsted spinning?

  1. Fibres are always spun on a ring frame with a condenser
  2. Fibres are drawn twice with gill boxes before roving
  3. Fibres are combed to remove short fibre and lie parallel
  4. Fibres are carded and condensed without combing, giving a bulky yarn Correct answer.

Explanation

Woollen spinning uses carding and condensing without combing, so short fibres remain and the yarn is softer and bulkier with less parallel fibre arrangement. Worsted spinning includes combing and gilling to align long fibres. The other options describe worsted or incorrect process details.

Question 37Yarn Manufacture and Spinning

Which condition promotes the formation of a good fibre ribbon in the rotor spinning fibre channel?

  1. Wet sliver fed to the opening roller
  2. Large rotor diameter with slow rotation
  3. High opening roller speed with a smooth, well-aligned fibre channel Correct answer.
  4. Low opening roller speed and high trash content

Explanation

High opening roller speed individualises fibres well, and a smooth, properly aligned channel allows them to assemble into a uniform ribbon at the rotor groove. Poor opening or a rough channel causes tufts and irregular yarn. Wet sliver and slow rotor rotation impair the process.

Question 38Yarn Manufacture and Spinning

What does the term 'twist multiplier' represent in yarn engineering?

  1. The percentage of short fibre removed during combing
  2. The number of fibres in the yarn cross-section
  3. The ratio of twist per unit length to the square root of yarn count Correct answer.
  4. The ratio of yarn diameter to fibre diameter

Explanation

The twist multiplier relates twist to yarn count through the square root relationship, allowing comparison of twist levels across different counts. It is used to set twist for a given yarn count and end use. The other definitions describe unrelated yarn parameters.

Question 39Yarn Manufacture and Spinning

A 30 tex yarn is required to have a twist of 800 turns per metre. Using the twist multiplier formula T = α × √(tex), what approximate twist multiplier α applies?

  1. α ≈ 27
  2. α ≈ 24000
  3. α ≈ 800
  4. α ≈ 146 Correct answer.

Explanation

Rearranging T = α × √(tex) gives α = T / √(tex). The square root of 30 is about 5.48, and 800 divided by 5.48 is approximately 146. This confirms the twist multiplier is a count-independent measure of twist level.

Question 40Yarn Manufacture and Spinning

Which spinning method produces yarn by wrapping fibres around a core using an air jet and a hollow spindle?

  1. Air-jet spinning Correct answer.
  2. Friction spinning
  3. Ring spinning
  4. Rotor spinning

Explanation

Air-jet spinning uses high-pressure air jets to wrap surface fibres around a core of parallel fibres, with a hollow spindle guiding the yarn. Ring and rotor spinning insert true twist by mechanical means, and friction spinning uses a perforated drum. The distinctive wrapping action identifies air-jet spinning.

Question 41Yarn Manufacture and Spinning

Why is a condenser used in carding for woollen spinning?

  1. To comb the fibres to remove short fibre
  2. To insert twist into the sliver
  3. To split the carded web into narrow strips and rub them into a condensed sliver Correct answer.
  4. To blend different coloured fibres

Explanation

In woollen carding the doffer web is split into narrow strips that are rubbed or condensed into a slubbing, which is then spun. This condensation gives the woollen yarn its characteristic structure. Combing, twisting and blending are separate operations.

Question 42Yarn Manufacture and Spinning

Which yarn fault is most directly associated with a damaged or wrongly set traveller in ring spinning?

  1. Slubs from undrafted fibre clumps
  2. Periodic thick and thin places
  3. Irregular twist and yarn breaks Correct answer.
  4. Neps in the yarn

Explanation

A damaged or wrongly weighted traveller causes erratic friction and tension, leading to irregular twist insertion and frequent breaks. Neps originate in carding, periodic faults from defective drafting rollers, and slubs from fibre clumps. The traveller's role in twist and tension makes it responsible for twist irregularity and breaks.

Question 43Yarn Manufacture and Spinning

What is the effect of increasing the draft in the drafting zone on fibre control if roller settings remain unchanged?

  1. Short fibres become better controlled and yarn evenness improves
  2. Short fibres become less controlled and yarn irregularity increases Correct answer.
  3. Twist insertion increases proportionally
  4. Fibre parallelisation increases without any effect on evenness

Explanation

Higher draft increases the speed difference between rollers, so short fibres outside the control of the roller nip float and produce irregularity. Correct roller setting and suitable aprons are needed to maintain control. Draft therefore interacts strongly with fibre length and roller spacing.

Question 44Yarn Manufacture and Spinning

Which statement correctly describes the difference between carded and combed cotton yarns?

  1. Combed yarns are produced without any drafting
  2. Combed yarns contain more short fibre and are weaker
  3. Carded yarns are always finer than combed yarns
  4. Combed yarns are smoother, stronger and more even due to short fibre removal Correct answer.

Explanation

Combing removes short fibre and neps, leaving longer fibres that produce smoother, stronger and more even yarns, usually at finer counts. Carded yarns retain short fibre and are less regular. Combed yarns still require drafting, so the other statements are incorrect.

Question 45Yarn Manufacture and Spinning

In the context of yarn numbering, what does a direct (fixed-weight) system express?

  1. The twist per unit length
  2. The number of fibres per cross-section
  3. The mass per unit length of yarn Correct answer.
  4. The length per unit mass of yarn

Explanation

Direct systems such as tex express mass per unit length, so a higher number means a coarser yarn. Indirect systems such as cotton count express length per unit mass, where a higher number means a finer yarn. Fibre number and twist are separate parameters.

Question 46Yarn Manufacture and Spinning

Which combination of fibre properties gives the highest yarn tenacity for a given twist level?

  1. Low fibre fineness and low fibre length
  2. Low fibre length and high fibre fineness
  3. High fibre length and high fibre strength Correct answer.
  4. High fibre crimp and low fibre strength

Explanation

Longer fibres provide more contact length and better twist efficiency, while stronger fibres raise the load at which the yarn breaks. Together they maximise yarn tenacity. Low strength, short length or coarse fibres reduce tenacity.

Question 47Yarn Manufacture and Spinning

What is the principal reason for using a compact spinning attachment on a ring frame?

  1. To condense the fibre strand and reduce the spinning triangle, lowering hairiness Correct answer.
  2. To eliminate the need for roving
  3. To replace the traveller with an air jet
  4. To increase spindle speed beyond the traveller limit

Explanation

Compact spinning uses pneumatic suction to condense the drafted strand before twisting, narrowing the spinning triangle and trapping protruding fibres. This reduces hairiness and improves strength and evenness. It does not remove the traveller or the roving supply, nor does it bypass the fundamental speed limit.

Question 48Yarn Manufacture and Spinning

A rotor-spun yarn is found to have lower tenacity than a ring-spun yarn of the same count. Which explanation is most consistent with the structure of rotor yarn?

  1. Rotor yarn contains no twist at all
  2. Rotor yarn is made only from synthetic filaments
  3. Rotor yarn has a more parallel fibre arrangement with higher twist efficiency
  4. Rotor yarn has a layered structure with more wrapper fibres and less fibre migration Correct answer.

Explanation

Rotor yarn forms a core-sheath structure with many wrapper fibres and limited fibre migration, so fewer fibres contribute fully to the tensile load. Ring yarn has a more helical, migrating structure with better twist efficiency. This structural difference explains the lower tenacity of rotor yarn at equal count.

Question 49Fabric Formation (Weaving, Knitting, Nonwoven)

In plain weave, what is the minimum number of harnesses required to weave the structure on a conventional loom?

  1. Four
  2. Three
  3. Two Correct answer.
  4. Six

Explanation

Plain weave alternates every pick, so the ends must be divided into two groups that rise and fall in opposition. Two harnesses, one for the odd-numbered ends and one for the even-numbered ends, are therefore sufficient. Additional harnesses add nothing to a true plain-weave repeat.

Question 50Fabric Formation (Weaving, Knitting, Nonwoven)

A woven fabric is described as having a 3/1 twill. What does this designation mean?

  1. Each warp end floats over three picks and under one pick Correct answer.
  2. Three picks are inserted between each weft float
  3. The fabric contains three warp colours and one weft colour
  4. Each weft floats over one end and under three ends

Explanation

In twill notation the first figure gives the number of ends a warp yarn passes over and the second gives the number it passes under, before the progression moves one end. A 3/1 twill therefore shows long warp floats on the face and short weft floats on the back.