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

Answer 2

Manufacturing process

Engineered for reason

Question 3

spinning

Answer 3

Specialised 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 submerges in a chemical bath which precipitates the fibre as it comes out of the spinneret e.g. acrylic, rayon etc

Question 5

dry-jet spinning

Answer 5

Extrudes solution in air, dry’s it and then 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 of 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 solidify 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. polythene, Aramis

Question 10

electrospinning

Answer 10

Uses electrical charge to draw very fine fibres from polymer liquid

Question 11

modification ratio

Answer 11

Industry recognised

The size of the outer circles circumference of the fibre is compared to the size of the inner circle circumference

Question 12

see powerpoint for

Answer 12

circumferences

Question 13

modification ration =

Answer 13

x/y

Question 14

a fibre with a round cross section has what MR

Answer 14

1

Question 15

what does modification ratio affect

Answer 15

flexibility and soil accumulation/hiding of the fibre

Question 16

see powerpoint for

Answer 16

method of determining the modification ratio

Question 17

the larger the modification ratio..

Answer 17

• The more likely the fibre shape can trap and hold soil

- More likely have premature crushing and matting

Question 18

MR of <2.2 is recommended for what

Answer 18

medium to high soil area

Question 19

MR of <1.5 is recommended for what

Answer 19

high to very high soil area

Question 20

trilobal shapes hold soil

Answer 20

Fibred with four holes, diffuse the light and provide soil hiding

The smooth outer surface with no grooves enhances soil release with vacuuming

Dirt cannot get into the holes of the hollow filament fibre. The holes are one ten thousandth of an inch, dirt particles are much, much larger

The best basis for discrimination of trilobal fibres is the modification ratio

Very discriminating

Question 21

Wayne Williams murder investigation

Answer 21

America serial killer “Atlanta child murders” 1979-1981 killed 11 young men

Prosecutors matched 19 different sources of fibres from William’s home and car to the victims including an unusual trilobal carpet fibre

Chemists from Du Pont testified about fibre manufacture

Fibre traced to Wellman Inc. a Boston textile company who designed fibre of a particular shape to get around Du Pont patent

Question 22

see powerpoint for

Answer 22

fibre cross sections

Question 23

see powerpoint for

Answer 23

methods used for analysis of automobile carpet fibres

Question 24

galaxy

Answer 24

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 25

poseidon

Answer 25

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 26

verdi

Answer 26

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 27

outlast

Answer 27

Viscose Fibre with benefits of viscose, e.g. soft, fine feel – similar to cotton or silk, absorbtion 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 28

UV/VIS spectra vs fluorescence spectroscopy

Answer 28

• 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.

Question 29

ring vs exhaustive dying

Answer 29

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

Question 30

what are spherulites

Answer 30

• Spherical semi crystalline regions inside non-branched linear polymers

Question 31

formulation of spherulites

Answer 31

• Their formation is associated with crystallisation 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

Question 32

what are spherulites composed of

Answer 32

highly ordered lamellae, which result in higher density, hardness, but also brittleness of the spherulites as compared to disordered polymer

Question 33

lamellae in spherulites are connected by

Answer 33

amorphous regions which provide certain elasticity and impact resistance.

Question 34

birefringence

Answer 34

Alignment of the polymer molecules within the lamellae results in birefringence producing a variety of coloured patterns

Question 35

birefringence is dependent on

Answer 35

Refractive index on the polarisation and direction of light)

Question 36

see powerpoint for

Answer 36

diagrams of spherulites

Question 37

size of spherulites

Answer 37

varies in a wide range, from micrometres up to 1 centimetre

• Mechanical properties

Question 38

mechanical properties of spherulites

Answer 38

• Formation of spherulites affects many properties of the polymer material; in particular crystallinity, density, tensile strength and Young’s modulus of polymers increase during spherization. This increase is due to the lamellae fraction within the spherulites, where the molecules are more densely packed than in the amorphous phase

Question 39

see powerpoint for

Answer 39

graph os isotopic polyporylene

Question 40

optical properties of spherulites

Answer 40

• 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 polarisers in optical microscope

Question 41

Polyacrylonitrile (PAN) fiber spun at high coagulation bath temperature (60 °C), containing macrovoids.

Answer 41

Coagulation bath hardens viscous polymer strands into solid fibers after extrusion through spinneret in wet spinning

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.

Question 42

what is yarn

Answer 42

Group of fibers or filaments that are interlocked together to form a long continuous strand

Either natural or man-made

Question 43

natural yarn

Answer 43

wool, silk . . (animal – slightly elastic, breathable, warm)

cotton . . . . . (less elastic, stronger),

hemp . . . . . .(plant) – can shrink, stain, etc. but also easy to dye

Question 44

man made yarn

Answer 44

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

Question 45

see powerpoint for

Answer 45

S and Z twist yarn