Appearance of fibres Flashcards
(33 cards)
1
Q
Longitudinal appearance
A
- Smooth, striated
- Inclusive e.g. dye, wax
- Texturing e.g. crimping process
2
Q
Cross sections
Results from-
A
- 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
3
Q
Spinning
A
- 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
4
Q
Wet spinning
A
- 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
5
Q
Dry wet spinning
A
- Extrudes solution in air, dry’s it and the submerges it in liquid bath e.g. lyocell spinning of dissolved cellulose
6
Q
Dry spinning
A
With hot air on spinneret solidifying fibres by evaporation solvent
7
Q
Extrusion spinning
A
- Pellets of solid polymer are melted by an extrusion screw then fed via pump to spinneret
8
Q
Melt spinning
A
- Fibres solidifying by cooling on exiting spinneret e.g. nylon polyester, saran
9
Q
Gel spinning
A
- Of high strength fibres uses a polymer gel where polymer chains are orientated so large intermolecular forces e.g. polyethene, Aramis
10
Q
Electrospinning
A
- Uses electrical charge to draw very fine fibres from polymer liquid
11
Q
Modification ratio
A
- Industry recognized
- The size of the outer circles circumference of the fibre is compared to the size of the inner circles circumference
look at ppt
12
Q
what does modification ratio affect
A
flexibility and soil accumulation/hiding of the fibre
13
Q
modification ratio equation
A
Modification ratio = x/y
- A fibre with a round cross section has MR=1
look at ppt
14
Q
the larger the ratio
A
- 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
15
Q
what do more trilobal shapes hold
A
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
16
Q
fibre cross sections
A
look at ppt
17
Q
whats the best basis for discrimination of trilobal fibres
A
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
18
Q
number of automoible carpets that possessed a particular cross sectional shape
A
look on ppt
- 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%.
19
Q
- Comparison of the modification ratio (in triplicate) of a single nylon fiber from a Nissan Maxima 1996
A
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.
look at ppt
20
Q
Methods used for analysis of automobile carpet fibres
A
look at ppt
21
Q
galaxy
A
- 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.
22
Q
poseidon
A
- 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
23
Q
verdi
A
- 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
24
Q
outlast
A
- 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.
25
- Morgan et al.together with the FBI May 2004
showed that UV/VIS spectra could not distinguish between 3 red polyester fibres but that fluorescence spectroscopy could.
26
ring vs exhaustive dying
- 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
look on ppt
27
spherulites
- 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
28
Alignment of the polymer molecules within the lamellae results in
birefringence producing a variety of coloured patterns
(Birefringence is dependence of Refractive index on the polarisation and direction of light)
look at ppt
29
Polypropylene spherulites
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
30
Mechanical properties
- 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
look at ppt
31
optical properties
- 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
32
circular cross section determined by
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.
33
yarn
- 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:
look at ppt
