Appearance of fibres

Question 1

Longitudinal appearance

Answer 1

• Smooth, striated
• Inclusive e.g. dye, wax
• Texturing e.g. crimping process

Question 2

Cross sections

Results from-

Answer 2

• Manufacturing process e.g. dog bone shape or orlon due to evaporation of organic solvent
• Engineered for reason e.g. melt spun nylon can be engineered in many difference shapes usually circular. Trilobal shapes with rounded edges used for carpets as enhances lustre, multichannel shapes transport moisture, hollow filaments reduces bulk

Question 3

Spinning

Answer 3

• Specialized form of extrusion that uses a spinneret to form multiple continuous filaments. Polymer must be in fluid form either by melting or dissolving in a solvent and then forces through the spinneret

Question 4

Wet spinning

Answer 4

• Oldest process and the polymer is dissolved in a solvent and the spinneret submerged in a chemical bath which precipitates the fibre as it comes out of the spinneret e.g. acrylic, aramid, modacrylic and spandex

Question 5

Dry wet spinning

Answer 5

• Extrudes solution in air, dry’s it and the submerges it in liquid bath e.g. lyocell spinning of dissolved cellulose

Question 6

Dry spinning

Answer 6

With hot air on spinneret solidifying fibres by evaporation solvent

Question 7

Extrusion spinning

Answer 7

• Pellets of solid polymer are melted by an extrusion screw then fed via pump to spinneret

Question 8

Melt spinning

Answer 8

• Fibres solidifying by cooling on exiting spinneret e.g. nylon polyester, saran

Question 9

Gel spinning

Answer 9

• Of high strength fibres uses a polymer gel where polymer chains are orientated so large intermolecular forces e.g. polyethene, Aramis

Question 10

Electrospinning

Answer 10

• Uses electrical charge to draw very fine fibres from polymer liquid

Question 11

Modification ratio

Answer 11

• Industry recognized
• The size of the outer circles circumference of the fibre is compared to the size of the inner circles circumference

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Question 12

what does modification ratio affect

Answer 12

flexibility and soil accumulation/hiding of the fibre

Question 13

modification ratio equation

Answer 13

Modification ratio = x/y
- A fibre with a round cross section has MR=1

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Question 14

the larger the ratio

Answer 14

• More likely the fibre shape can trap and hold soil
• More likely have premature crushing and matting
• MR <2.2 is recommended for medium to high soil areas
• MR <1.5 is recommended for high to very high soil areas

Question 15

what do more trilobal shapes hold

Answer 15

soil

• Fibre with four holes, (run the entire length of the fibre), diffuse the light and provide soil hiding
• The smooth outer surface with no grooves enhances soil release with vacuuming
• Dirt can not get into the holes of the hollow filament fibre. The holes are one tenth thousandth of an inch, dirt particles are much larger

Question 16

fibre cross sections

Answer 16

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Question 17

whats the best basis for discrimination of trilobal fibres

Answer 17

the modification ratio

• Very discriminating
• Helped in a major court decision- Wayne Williams murder investigation
• American serial killer ‘Atlanta’s child murders’ 1979-1981 killed 11 young men
• Prosecutors matched 19 different sources if fibres form Williams home and car to the victims including an unusual trilobal carpet fibre
• Chemist form Du Pont testified about fibre manufacture
• Fibre traced to Wellman inc. a Boston textile company who designed fibre of a particular shape to get round Du Pont patent

Question 18

number of automoible carpets that possessed a particular cross sectional shape

Answer 18

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• Modification ratio calculations ranged from 1.9 to 3.0
• The overall discrimination of all trilobal fibers based on modification ratio was 48.5 percent.
• The diameter for trilobal fibers ranged from 33.8μm to 65.3μm. The overall discrimination based on diameter was 47.3%.

Question 19

• Comparison of the modification ratio (in triplicate) of a single nylon fiber from a Nissan Maxima 1996

Answer 19

to the experimental mean was accurate.

• Values are compared with the average, standard deviation and confidence intervals for the 1996 Nissan Maxima modification ratios calculated from a standard.
• The confidence intervals overlap and the t-test showed that the means are similar.

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Question 20

Methods used for analysis of automobile carpet fibres

Answer 20

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Question 21

galaxy

Answer 21

• Trilobal Viscose Fibre with High Absorbency
• Y design increases the absorption capability of nonwoven structures.
• main application in the manufacture of tampons, the global market leader.
• Also used in standard nonwoven processes such as dry laying or spunlacing.

Question 22

poseidon

Answer 22

• Viscose fibre with an ion exchange functionality which can be fully regenerated.
• Much higher active surface area, than traditional bead resins permitting an increased rate of ion exchange.
• Can be exchanged with silver or copper ions

Question 23

verdi

Answer 23

• Anionic Viscose Fibre with a Defined Core-Sheath Structure results in an increased absorbency of water vapour: moisture management in textiles.
• Non-sticking fibre surface in wet state allows use in wound-dressings.
• Exhibits self extinguishing properties

Question 24

outlast

Answer 24

• Viscose Fibre with benefits of viscose, e.g. soft, fine feel – similar to cotton or silk, absorption of moisture, hygienicic while also providing temperature-buffering
• Fibres contain micro-encapsulated phase-change materials,‘Thermocules’, which store, absorb and release heat.
• Used for clothing and beadspreads, blankets or mattress covers.

Question 25

• Morgan et al.together with the FBI May 2004

Answer 25

showed that UV/VIS spectra could not distinguish between 3 red polyester fibres but that fluorescence spectroscopy could.

Question 26

ring vs exhaustive dying

Answer 26

• Confocal laser scanning microscopy cross sections of polyethylene terphthalate (PET) fibres dyed with 8% of dye BzDF1 as a function of increasing temperature and time in the dyebath
• 80°C (ii) 90°C (iii) 100°C
• (iv) 110°C (v) 120°C (vi) 130°C
• Then at different times (mins) at 130°C
• (vii) 20min (ix) 40min (x) 60min
• (xi) 80min (xii) 100min (xiii) 120min

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Question 27

spherulites

Answer 27

• Spherulites are spherical semi crystalline regions inside non-branched linear polymers
• Their formation is associated with crystallization of polymers from the melt and is controlled by several parameters such as the number of nucleation sites, structure of the polymer molecules, cooling rate, etc
• Spherulites are composed of highly ordered lamellae, which result in higher density, hardness but also brittleness of the spherulites as compared to disordered polymer
• The lamellae are connected by amorphous regions which provide certain elasticity and impact resistance

Question 28

Alignment of the polymer molecules within the lamellae results in

Answer 28

birefringence producing a variety of coloured patterns
(Birefringence is dependence of Refractive index on the polarisation and direction of light)

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Question 29

Polypropylene spherulites

Answer 29

Round and dark – α variety (common)
Bright and irregular –β variety ( less common)
Formed on slow cooling allowing time for allignment
The size of spherulites varies in a wide range, from micrometers up to 1 centimeter

Question 30

Mechanical properties

Answer 30

• Formation of spherulites affects many properties of the polymer material: in particular crystallinity, density, tensile strength and young’s modulus of polymers increase spherulization. This increase is due to the lamellae fraction within the spherulites, where the molecules are more densely packed than in the amorphous phase
• % elongation at failure
• e.g. 100% strain at failure means that a 10cm sample of PP will be 20cm long when it breaks.
• Strain-at-failure vs spherulite size
• Too many spherulites and polymer will crack under load

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Question 31

optical properties

Answer 31

• Spherulites can scatter light rays and hence the transparency of a given material decreases as the size of the spherulites increases.
• Alignment of the polymer molecules within the lamellae results in birefringence producing a variety of coloured patterns when spherulites are viewed between crossed polarizers in an optical microscope

Question 32

circular cross section determined by

Answer 32

 relative diffusion of solvent out and non-solvent in the filaments during coagulation.
 When the flux of solvent outward is less than the inward flux, the filament swells and a circular cross-section can be expected.
 occurs at high coagulation bath temperatures and high solvent content in the coagulating bath. Cross sections are round at 50 °C or above.
 However, high bath temperatures give an increase in void content and subsequent decrease in fiber density, resulting in poor fiber properties.

Question 33

yarn

Answer 33

• Group of fibers or filaments that are interlocked together to form a long continuous strand
• Either natural or man-made, most commonly:
  Natural: wool, silk . . (animal – slightly elastic, breathable, warm) cotton . . . . . (less elastic, stronger), hemp . . . . . .(plant) – can shrink, stain, etc. but also easy to dye

Man-made: polyester, nylon . . – can be stronger than natural yarns. – May
be finished with wax or alternative coatings allowing for durability during sewing process and during its’ wear and tear in garment – S and Z twist yarn:

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