fibre analysis Flashcards
what is tenacity
overall structure of a fibre
what is durability
the ability of a fibre to withstand rubbing or friction
what are pilling properties
the formation of balls of loose fibres on the surface of a fabric resulting from abrasion
what is dimensional stability
The ability of a fibre to maintain its original shape, neither shrinking nor stretching
what is elastic recovery
The ability of a fibre to return to its original length after it is stretched
what is creep
how the fibre response to a constant stretching force
what is flexibility
The ease by which fibres can be bent of folded which affects the overall drape
what is resilience
how easily a fibre returns to original state after creasing
what is absorbency
the ability of a fibre to tale in moisture
what are thermal properties
how well the fibre insulates the wearer
what are the two fibre types
natural
synthetic or man-made
what are the three natural fibres
animal
vegetable
mineral
animal fibres
proteinaceous materials
subdivided into 3 groups according to their structure
silks (fibroin), wool (keratin) and hair (keratin)
vegetable fibres
subdivided into 3 groups according to derivation
seed fibres, bast (stem) and leaf fibres
seed fibres = cotton, kapok and coir
bast or stem fibres = flax, ramie, hemp and jute
leaf fibres = sisal, abaca and new Zealand hemp
give one example of a mineral fibre
asbestos
what type of fibre is silk
animal
silk
obtained from larvae of silk moth
Silk is spun from 2 glands in the mouthparts of the creature
Produces two individual strands which are then encased in a protein known as sericin
what type of fibre is wool and hair
animal
wools and hair
Variety of sources from the most common ovine Wool (sheep) to unusual wool such a Chiengora (dog)
Animal fibres of this type are primarily composed of the protein keratin made of sulphur rich amino acids but varies by species and even diet
ovine (sheep) wool
Soft, strong, elastic, warm, breathable and comparatively inexpensive
All wools show obvious signs of scaly morphology and the number of scaled will vary by breed of sheep
cross section shows round morphology
medulla cells
often dead and air filled
cortical cells
spindle shaped cells packed together
cuticle cells
forming a tough outer sheath of top facing overlapping scaled which vary between and hence can be fairly discriminating
vegetable fibres
Primarily cellulose with the addition of hemicellulose, lignin’s, pectin’s, water soluble proteins, fats and waxes
Significant differences found in fibre length, diameter, cell wall shaped and general appearance
what type of fibre is cotton
vegetable
what type of fibre is hemp
vegetable
cotton
strong, soft, elastic, warm, breathable
The fibre is easily dyed with a range of materials allowing a huge range of colours to be produced
asbestos
Asbestos is a naturally mineral fibres used in a variety of applications
A generic term for a number of silicate fibre types with high elasticity and high resistance to corrosion, wear and tear and heat… It will not burn
Used industrially where it was once mixed with concrete and other materials to produce fire resistant board, insulation etc.
Remains used in some friction materials and some fireproofing
what are man-made chemicals derived from
petrochemicals
synthetic fibres
The aim is to produce something that replicates natural fibres, but either improves upon some of the limitations of the original or produces a cheaper alternative
Improvements may include greater tolerance to chemical action, heat, shrinkage, greater strength, greater absorbency or less practically, improved appearance, texture or the greater ability to be permanently coloured
which two sources can semi-synthetic fibres be regenerated from
biological
mineral
cellulose fibres - semi-synthetic fibre
common of regenerated fibres
sub-classes of it
viscose rayon - semi-synthetic fibres
inexpensive
very soft, comfortable
weak with poor abrasion and low wet strength
viscose rayon manufacture - semi-synthetic fibres
cellulose material - wood pulp
treated with NaOH
treated with CS2 forming sodium cellulose xanthate
little water and NaOH added, viscous liquid formed and then extruded in hardening bath
hardening bath consists of H2SO4, sodium and zinc sulphates and glucose
lyocell-tercel
semi-synthetic fibres
modern variant of viscose
performs well with soft, strong, wrinkle resistant fibre with strong water absorption properties
fibre obtained direct from solvent without derivative formation
raw bleached cellulose dissolved in N-methylmorpholine N-oxide
material extruded and drawn in air after which they are set in dilute amine oxide which hardens the fibres
can be washed or dried and undergo any post-processing
cellulose esters -diacetate and triacetate
semi-synthetic fibres
soft smooth fibres which dries quickly and has lustrous appearance and is colourfast
acetate performs badly as it distorts and wrinkles very easily, has poor thermal properties and is weak fibre so dry clean only
raw bleached cellulose reacts with acetic anhydride, acetic acid and sulphuric acid which acetylates the hydroxyl groups
undergoes controlled hydrolysis to produce dictate or triacetate
dissolved in acetone or other solvent and extruded into fibres
spinning
made-made fibres
polymer is prepared in a concentrated, viscous form, either in a solvent or in some molten state
material extruded through tiny holes in a device known as a spinneret, a plate with a number of precision bored holes
spinneret can produce fibres of various shapes and diameters giving rise to fibres with variable cross sections although in practise this is normally carried out with melt spun fibres
wet spinning
used for polymers which need to be dissolved in a solvent for spinning such as acrylic, rayon, aramid and modacrylic
spinneret generally submerged in a bath containing a solution which causes the emerging fibres to precipitate and solidify to strands
strands are then taken up and are normally drawn to increase their strength and align the polymers chain in the same direction thereby increasing fibre tenacity
setting solution varied according to the fibre being manufactured and is normally sulphuric acid for rayon or thiocyanate for acrylic
dry spinning
used for polymers which need to be dissolved in a solvent for spinning such as acetate and triacetate and acrylic
instead of the spinneret being submerged in a chemical bath, it lies at the top of a warmed chamber
as the material emerges from the spinneret, the solvent evaporates causing the polymer to coagulate and form individual fibres
hot air of warmed inert gases carry the solvent away where it can be recovered and reused
strands are taken up and normally drawn
melt spinning
simplest of all processes and one used for polymers which can be melted such as nylons, polyester and various others
polymer, in pellet form is melted in an inert atmosphere and then forced through the spinneret into a cooling chamber
strands are then taken up and normally drawn to increase overall strength
cross sectional shape is easily controlled using spinning which is a very useful point for fibre identification
spinning - cross sectional shape
fibre cross sectional shape may be result of spinning process where the process causes fibres to become crenelated
with melt spun fibres it is possible to engineer the fibre cross section to produce certain specific properties such as treated softness of wicking
round cross sectional shape
no major longitudinal striations uniform diameter
bilobal cross sectional shape
kidney or dog-bone shaped single of double striation
trilobal cross sectional shape
parallel striations that appear to move
hollow cross sectional shape
single continuous hollow forming a black core
complex cross sectional shape
multiple striation appearing irregular
delustrant
man made fibre
Engineering fibre shape and cross section can help to alleviate the problem to some extent but may not always lead to favourable hand
It is possible to include materials that help dampen the lustre of fibres and in most cases this is Anatase
Not only does Anatase help prevent light reflection, but its inclusion may also roughen the fibre surface dampening reflectivity
Delustrant appears as dark coloured ‘dots’ within the fibre matric and the size, shape, appearance, abundance and general distribution are useful for comparative purposes
Although the presence of delustrant does not serve to identify a specific fibre type, it is a useful indicator of man-made fibre and may be use as a comparison tool
condensation polymerisation
chemical condensation reaction in which water or acid is produced as a by-product
addition polymerisation
produced by joining molecules using a double bond or free radical reaction
polyamides - nylon 6,6 and nylon 6
synthetic fibre
Soft, smooth fibres with controllable lustre
High strength fibres with god abrasion resistance and elastic recovery
Uncommon in modern clothing but used for manufacture of seatbelts, tire cord, ropes and other high strength materials including gun parts
Resists attack by some chemicals, molds and mildew
A fibre derived from simple pre-cursor organic materials
Produced in two forms: nylon 6,6 and nylon 6
polyamide nomex and kevlar
synthetic fibres
Aromatic polyamides having at least 85% of their amide linkage directly attached to two aromatic rings
By comparison to traditional fibres, aramids lack the properties requires to produce soft, comfortable fashionable clothing
Both fibres are extremely strong with good abrasion resistance
polyamides - acrylic
Smooth, soft warm fibres comparable to wool although considered a bit on the cheap side
Moderate strength fibres with fair abrasion resistance
May be seen in jumpers, hats, rugs, curtains and various plastic items such as garden furniture
Light and chemical resistant but flammable and staticky
Fibre derived from acrylonitrile and a copolymer which are polymerised and dissolved in a solvent
The material produced then undergoes dry spinning or wet spinning in a bath of dilute solvent
polyamides - dynel and verel
Many of the same properties as acrylic and similar uses
However modacrylic is somewhat flame retardant and will self extinguish
Modacrylic is as the name suggests a modified acrylic fibre where between 35% and 85% of the fibre consists of polyacrlonitrile monomer units and the remainder consists of some other sub-unit
This is normally vinyl chloride, vinylidene chloride or vinyl bromide
Once polymerised, the fibre is dissolved in solvent and dry spun
acid dyes
polyamides, wools, silk and polypropylene
azo dyes
cellulosic fibres
what type of fibre does dye come under?
man-made
basic dyes
acrylics, polyester and polypropylene
direct dyes
cellulosic fibres
disperse dyes
polyester and acetate
metaliised dyes
wool
sulphur dyes
cellulosic fibres
vat dyes
cellulosic fibres- denim
pigment
polypropylene, viscose, acrylic, polyamide and polyester
what are pigments
insoluble particles of strong colour which are normally added to the melt during spinning
clearly man-made fibre normally melt spun
when is the dying process completed
after spinning to may factor as part of the spinning process
what are the 3 things used to identify dyes
CI number
generic name
commercial name
CI number in dyes
all dyes are given a 5 digit colour index number of CI number
dyes which come as multiple salts may include a sixth
generic name in dyes
all dyes are given a generic name which may indicate use
commercial name in dyes
comes from the manufacturer
before silk fibres can be used
Before the fibres can be used, sericin casing is degummed by dissolving in dilute alkaline revealing two translucent fibres of triangular cross section
Composed of the protein fibroin, which is rich in alanine, glycine and serine and contains no sulphur containing amino acids
Doesn’t have the same unpleasant smell as burning as hair fibres
what percentage of cotton is cellulose
95
cotton after maturation
the fibre walls shrink, and the central hollow lumen becomes smaller and flattens which evokes convolutions or twist which improves flexibility and allows better interlocking in yarn
mercerisation in cotton
Can be treated in a process called mercerisation in which the fibre is treated with NaOH and elongated causing the fibre to swell
Produces a more lustrous, softer, stronger fibre that takes up dye better
nylon 6,6
Nylon 6,6 is produced from a condensation reaction between adipic acid and hexamethylene diamine, the 6,6 comes from the use to two 6C precursors, the reaction is a simple condensation
nylon 6
Nylon 6 is slightly inferior in its properties particularly in regard to its melting point
Nylon 6 is produced from a ring opening reaction between molecules of caprolactam – the 6 comes from the use of a single 6C precursor, the reaction is a ring opening forming a linear chain polymeric molecule
nomex
Nomex has excellent thermal resistance properties and is used in flame retardant properties and is used in flame retardant clothing for pilots, firefighters and racing drivers
Nomex is produced from a condensation reaction between meta-phenylenediamine and isophthaloyl chloride producing HCl condensate
kevlar
Kevlar has incredible strength being on a weight for weight basis five times stronger than steel!
It is used far ballistic protection, stab resistance gloves, tyre ply and for top end racing sails
Kevlar is produced from para-phenylenediamine and terphthaloyl chloride producing very linear polymer chain of high strength
