Final Exam

Question 1

What is the flow chart of filament yarn processing?

Answer 1

Polymerization → Dissolving → Extrusion → Drawing → Texturing

Question 2

What are the reasons for mixing polymers in filament yarn processing?

Answer 2

• Polymers that cannot be dyed are mixed
• Blending fibers to get desired properties
• Enhances brightness
• Reduces degradation
• Increases conductivity

Question 3

What are the three primary spinning methods for filament yarn processing?

Answer 3

Melt spinning, Dry spinning, Wet spinning

Question 4

What is melt spinning?

Answer 4

A process where polymers are melted, extruded through a spinneret, solidified by cold air, and then collected.

Question 5

What are some examples of thermoplastic fibers used in melt spinning?

Answer 5

PET, Nylon, Polypropylene

Question 6

What are the advantages of melt spinning?

Answer 6

• High productivity
• No solvents required
• Ability to combine two or more materials

Question 7

What are the disadvantages of melt spinning?

Answer 7

Low tenacity (strength) and modulus (stiffness) of fibers.

Question 8

What is dry spinning used for?

Answer 8

Polymers that need to be dissolved in a solvent because they cannot be melted.

Question 9

What is the dry spinning process?

Answer 9

• Polymer dissolved in volatile solvent
• Solution is purified and extruded through a spinneret
• Fibers solidify as solvent evaporates in a warm chamber

Question 10

What are examples of fibers produced by dry spinning?

Answer 10

Acetate, Triacetate, Acrylic, Modacrylic, Spandex, Vinyon

Question 11

What are the advantages of dry spinning?

Answer 11

• High productivity
• Yarn does not need purification

Question 12

What are the disadvantages of dry spinning?

Answer 12

• More complex compared to melt spinning
• Flammable due to the use of volatile solvents

Question 13

What is wet spinning used for?

Answer 13

Polymers that do not melt and only dissolve in non-volatile or thermally unstable solvents.

Question 14

What is the wet spinning process?

Answer 14

• Polymer solution is extruded into a spinning bath
• Fibers coagulate in the bath and are collected

Question 15

What are examples of fibers produced by wet spinning?

Answer 15

Lycocell, PVC, Vinyon, Kevlar, Nomex, Spandex, Acrylic, Modacrylic, Zylon

Question 16

What are the advantages of wet spinning?

Answer 16

Can produce large tows (fiber bundles).

Question 17

What are the disadvantages of wet spinning?

Answer 17

• Low productivity
• Solvent needs to be washed out, making it resource-intensive

Question 18

What is gel spinning used for?

Answer 18

Producing high-strength and high-modulus fibers.

Question 19

What is the gel spinning process?

Answer 19

• Polymer is kept in a liquid state with a high degree of orientation
• Solution is extruded through spinnerets and cooled in solvent or water
• Yarn is then stretched

Question 20

What are examples of fibers produced by gel spinning?

Answer 20

Ultra-high molecular weight polyethylene, Polyvinyl alcohol, Polyacrylonitrile

Question 21

What are the characteristics of non-round cross-section fibers?

Answer 21

High surface area
High cover
Higher filtration efficacy
Higher liquid wicking
Higher sound insulation
Higher thermal insulation
High bend rigidity
Higher friction

Question 22

What is the purpose of drawing in filament yarn processing?

Answer 22

• Increases fiber strength
• Removes permanent elongation

Question 23

What factors affect the drawing process?

Answer 23

• Material type
• Spinning conditions
• Spinning take-up speed

Question 24

What is fiber tenacity?

Answer 24

Fiber tenacity is the normalized value used to compare fiber strengths, measured by dividing the breaking force by the fiber denier.

Question 25

What materials use high draw ratios for producing high-tenacity yarns?

Answer 25

Nylon, Polyester, Polypropylene, Gel-spun yarns

Question 26

What happens when the draw ratio increases?

Answer 26

Increases molecular orientation Increases yarn tenacity Decreases breaking elongation

Question 27

What are the end uses of high-performance fibers?

Answer 27

Protective clothing Aerospace Sports Industrial materials

Question 28

What are the advantages of synthetic yarns?

Answer 28

High strength High elongation and recovery Uniformity Resistance to mildew Easy care

Question 29

What are the disadvantages of synthetic yarns?

Answer 29

Too smooth Sticky Do not wick moisture Poor insulators

Question 30

What is texturing?

Answer 30

A post-extrusion process applied to flat continuous filament yarns to modify their structure for specific end uses like apparel.

Question 31

What does texturing improve in yarns?

Answer 31

Stretch Bulkiness Thermal insulation Wicking ability

Question 32

What modifications does texturing introduce to yarn?

Answer 32

Crimps Loops Knots

Question 33

What are the texturing methods?

Answer 33

False twist Stuffer box Knit-de-knit Air jet

Question 34

What is the false twist texturing process?

Answer 34

Flat thermoplastic yarn moves through a heating zone and is false twisted The yarn is cooled, the false twist is removed Yarn is overfed and wound into a package

Question 35

What is the stuffer box texturing process?

Answer 35

Filaments are stuffed into a heating box and crimped Heat is applied and then cooled to maintain the crimp

Question 36

What is stuffer box texturing used for?

Answer 36

Carpeting yarns

Question 37

What is the knit-de-knit texturing process?

Answer 37

Filaments are knitted into fabric A wavy configuration is created Knitting gauge and loop length determine the size and frequency of yarn waves

Question 38

What is air-jet texturing?

Answer 38

A process that creates crimps or loops through mechanical interlocking using an air jet.

Question 39

What types of yarns can use air-jet texturing?

Answer 39

: Any continuous filament yarns.

Question 40

Which texturing methods are used for thermoplastic continuous filament yarns?

Answer 40

False twist, Stuffer box, and Knit-de-knit.