PERFORMANCE CHARACTERISTICS OF MATERIALS Flashcards
Fibre production: cotton
Cotton is grown in tropical parts of the world. when the seed pods of the plant (bolls) ripen, the seeds inside bolls become covered with fine cotton fibres. When the seed pod eventually bursts, it becomes a fluffy ball.
As the sun dries the fibres, they collapse and become flatter like a ribbon, then twisted
How short are fibres in the cottons Boll
short, about 2-5cm in length
Fibre production: linen
Come from the stem of the flax plant. The stalk is made up of bundles of fibres surrounding a centre pith. The fibres are separated from the parts of the plant that are not wanted.
Linen fibre characteristics in production
smooth round hollow centered tubes with cross markings down their length, they are about 3-4cm long.
Fibre production: wool
wool mostly comes from sheep. the sheep are sheared and the fleeces are sent to the mills for processing.
other luxury wools come from other animals - cashmere from goats, mohair from angora goats, angora wool from angora rabbit.
how long are wool fibres
between 4 and 39 cm long, staple fibres
fibre production: silk
comes from the cocoon of the silk caterpillar. It spins the cocoon with two triangular shaped filaments, held together with natural gum (sericin) one from each side of its mouth. It can only be made into silk if its boiled before the caterpillar breaks free as a moth, because this can ruin the filaments.
(regenerated fibre production) how is spinning solution made
using wood pulp - its cleaned and the cellulose is pressed into sheets. The sheets are dissolved in a solvent to make a thick, sticky liquid (spinning solution)
how is spinning solution made into viscose fibres using a spinneret (wet spinning)
the spinning solution is filtered to remove any undissolved particles, then pumped through a spinneret. The spinnneret is immersed in a bath of chemicals, which solidify the visocse filaments as they emerge from small holes in the spinneret. The fibres solidify from the outside inwards at an irregular rate.
The filaments are stretched before being wound on to a spool as filament yarns, or cut into short staple lengths.
The shape of the holes in the spinneret can be changed to make fibres of different characteristics
(production) Melt spinning of synthetic fibres
synthetic fibres are made from chemicals that come from oil. the chemicals are made into a polymer which is cut into small pieces. These are melted to make a spinning solution that is then pumped though spinnerets.
As long filaments leave the spinneret, they are passed through a stream of cold air that solidifies them, before they are stretched out three or four times their og length
what happens to the long filament fibres often?
they are cut to shorter staple lengths so that they can be mixed with other staple fibres like cotton.
Technical and modern materials
a new material that has been developed from its original form. It has special qualities suited to specific uses, but its not a smart material
some examples of technical and modern materials
Gore-Tex, Kevlar, nomex, phosphorescent textiles, reflective (glass beads), coolmax, micro-encapsulated fibres, purista/chitopoly (protects against bacteria, fabrics with electronics, geotextiles, materials using nano-tech, microfibres
Phosphorescent materials
materials that glow in the dark by transforming invisible energy forms into light
how can phosphorescent materials be used in textiles?
phosphorescent dyes can be incorporated into synthetic fibres and yarns, used for printing pastes or applied as surface coating
what is phosphorescent materials most purpose
for high visibility safety clothing
micro-encapsulated fibres and fabrics
health and cosmetic chemicals can be incorporated into the hollow centres of microfibres. The chemicals are released slowly or absorbed the skin of the wearer.
example of micro-encapsulated fibres
those that release scents
ceramic and carbon fibres are used in the production of nano fibres, why?
they are extremely lightweight and very strong
how are nano-fibres made?
using an electro-spinning process and are collected in the form of sheets as big as a football pitch
what are the nano-fibre sheets used for
breathable membranes. They allow perspiration to pass out of sportswear garments, and at the same time, prevent large water droplets and other potentially harmful particles passing through
Where can carbon fibres also be used
in the production of electro-conductive fibres which are used to make intelligent fabrics or wearable computers
where can ceramic fibres also be used
when incorporated with synthetic firbes through encapsulating the fibre or coating, it can give a fabric UV protection or make fabrics that regulate body temperature
example of UV protective fabrics
Esmo, sunfit
example of body-temperature regulating fabric
thermolite
why do filament and staple fibres with need to be twisted with other fibres to make yarn?
staple fibres are too short and filament fibres are too fine
what determines the strength of a yarn
the level of twists - low levels mean weaker fibres, they slip apart and rougher to touch. High levels increase strength and makes it smoother and denser; it also increases price.
staple yarn
a yarn made from short staple fibres that are twisted together to form a yarn
filament yarns + what happens when they are twisted with staple fibres
a yarn made by lightly twisting one or more filament fibres together. The filament fibres need to be cut to the same length as staple fibres in order to be twisted with them.
what makes staple yarns good insulators + moisture trappers
they are hairy, textured and duller in appearance - making them good at trapping air between the fibres. meaning they are good insulators and will make warm fabrics
how are multifilament yarns made
lightly twisting continuous filament fibres together. e.g nylon/ polyester
how are mono-filament yarns made
from a single, continuous filament
why are filament yarns not good insulators
they are smooth and therefore do not trap air between fibres, meaning they are not good insulators
Plied yarn
yarn made by twisting single yarns together to make a thicker yarn
single yarns
has staple fibres or filament fibres twisted together to make one single yarn
what does a ply of a yarn refer to
the number of strands that make up the yarn. yarns with higher number of plies are more durable as plies hold yarn together
corded yarns are made by twisting yarns with more than 1 ply together, where are corded yarns commonly used?
sewing and embroidery threads or industrial yarns that need to be very strong
why are fibres blended and mixed?
manufacturers include different fibres in a blend to mix the properties and enable a product to be better suited to the product
How can fibres be blended?
spinning two or more fibres together to make yarn. fibres must be the same length. The cut fibres are cute to the proportions needed in the mix - e.g 70% polyester and 30% cotton blends.
core-spun yarn
a component yarn with a central core yarn covered by other fibres
what is core-spun used for
producing stretch yarns or sewing threads - the core provide strength whereas the outside fibre is weaker but used for aesthetic purposes
what is a mixture
often refers to a fabric that has been woven with different warp and weft yarns
Main reasons for blending
- help reduce fabric costs
- give different effects in the fabrics texture and handle
- allow for novelty effects when fabric is dyed
- make a fabric with specific qualities for a particular end use
- make a fabric stronger
- make a fabric easier to care for
- enable fabrics to be more crease resistant
- allow fabrics to be heat-set
popular blend examples
polyester-cotton (polyester cancels out shrinking and slow drying, the cotton makes it soft to skin)
elastomeric fibres with others (small amounts can give a lot of stretch to fabrics as well as crease resistant
wool blends (makes it soft and warm, other fibre can give strength and abrasion resistance
what will happen if a yarn is twisted too much
it will cause the yarn to untwist itself and untwist and snarl
what do the tex or denier of a yarn relate to
the thickness of the yarn
how are tex and denier measured
by weighing a specified length of the yarn
what are the two types of yarns
textured and fancy
what are textured yarns
a continuous filament yarn that has crimps, crinkles and snarls heat- set into the filament, can be synthetic
describe textured yarns
they are more interesting, they can carry water through fine tubes created in and between yarns. textured yarns are softer and make more comfortable fabrics with more volume and less lustre. They have more elasticity as the crinkles and snarls help the yarn stretch out