Fibres

Question 1

Define fibre

Answer 1

Fundamental unit used in making of textile yarns and later on into fabric. Any product capable of being woven or otherwise made into fabric. Can be natural or man made

Question 2

What is the role of a fibre examiner?

Answer 2

Determent textile present, identify/compare fibres, determine potential association and assess forensic significance

Question 3

What are the 2 types of fibres?

Answer 3

Natural (exist in nature as discrete fibres that have an origin. Tend to be 5-20mm long, easily distinguished under microscope. Most common cotton, Collected from source. Fabric made often fuzzy as individual fibres are short and stick out) and man made

Question 4

What are the 3 types of natural fibres?

Answer 4

Animal (obtained from animal. Protein based. High resiliency, weak when wet, bad conductors eg silk, wool), Vegetable (From plants, cotton based, low resilience, high density, good heat conductor, high absorbant and resistant to high heat. Cellulose base ue seed/frui, cotton, flac, jute) and Mineral (inorganic materials shaped into fibres. Are fireproof, resistant to acids and used for industrials purposes ie asbestos)

Question 5

What are the types of man made fibres?

Answer 5

Natural polymer (from natural poylmer source including cellulose, cellulose ester, protein, alginate and rubber. Raw materials processes, forced through spinning jet ie polyvinyl, polyurethane and polyester), synthetic polymer (from polymerisation of monomeric starting materials. Can be addition or condensation polymerisation eg polyethylene, acrylic, spandex) and others

Question 6

What are the 4 constitutions of synthetic polymers?

Answer 6

Simple polymer, Alternating co-polymer, Block co-polymer and graft co-polymer

Question 7

What are the 3 manufacturing man made fibre techniques?

Answer 7

Melt spinning polymer (melt at high temp, forced through spinneret, air jets cool polymer and solid filaments gathered), Dry spinning (polymer dissolved in volatile solvent, forced through spinnerets, warms gases allow solvent to evaporate leaving behind filament) and Wet spinning (polymer dissolved in solvent and solution forced through spinneret, filament emerges into bath that extract solvent)

Question 8

Define yarn

Answer 8

Strand of textile fibre in a form suitable for weaving, knitting, braiding , felting, webbing or otherwise fabricating into fabric. Can be constructed for more than one fibre type and needs to be separated to determine which fibre present. Have s, z and O twist

Question 9

Define thread

Answer 9

Product used to join pieces of fabric together

Question 10

What is warp and weft?

Answer 10

Warp is lengthwise yarn and weft is crosswise yarn

Question 11

When can dyes be added to fibres?

Answer 11

During fibre forming stage or after formation

Question 12

What are the dye types?

Answer 12

Acid dyes (wool, silk, nylon), basic (acrylic), direct (cotton), metallised (wool), vat (cotton), reactive (cotton, wool, nylon), disperse (acetate, nylon), azoic (cotton, viscose) and sulphur (cotton)

Question 13

What factors affect fibre transfer?

Answer 13

Area of contact, nature of contact, number of contact passes , nature of donor garment, nature of recipient garment

Question 14

What is the fibre transfer potential?

Answer 14

capacity of a textile surface to shed fibres or to act as a donor of textile fibres that may transfer onto other surfaces

Question 15

What is the fibre retention potential?

Answer 15

Capacity of a surface to retain textile fibres that have been transferred onto it

Question 16

What is differential shedding?

Answer 16

Blended fabric shedding giving actual fibre compared to ratio of fibre types

Question 17

What is primary and secondary transfer?

Answer 17

Primary is fibre transfer caused by direct contact between textile item and another item without any intermediate surface involved. Secondary is indirect transfer using another surface

Question 18

What is fibre persistence?

Answer 18

Less than 20% fibres remaining after 4 hrs. Fibres can lodge and hold or may fall off. Longer fibres get lost quicker

Question 19

What are some of the implications considered with fibres?

Answer 19

Need to collect clothing ASAP, contamination prevention protocols

Question 20

What are the 2 fibre recovery?

Answer 20

Background fibres, foreign fibres which can be crime related, user or non user

Question 21

What techniques are used on examination of fibres?

Answer 21

Microscopy, polarised light, fluorescnece, TLC, FTIR

Question 22

What are factors that strengthen fibre evidence?

Answer 22

Several fibres of sample type with significant length found to be indistinguishable from known source, fibre types/colours that are uncommon, fibres found in unexpected places, two way textile transfer

Question 23

What are factors that weaken fibre evidence?

Answer 23

Few fibres recovered, fibre type/colour is common, legitimate contact, failure to follow contamination prevention protocols