Yarns Flashcards
What must fibres be turned into before they can be woven or knitted into a fabric?
Into yarns
What is Yarn?
Continuous length of fibres that are interlocked and used to produce fabrics
What do twist do to a yarn?
Hold fibres together & give it strength
Compare a low level twists & a high level twists:
- what are each type of twist more suitable for?
- what type of twist should be used for a brushed fabric? why?
Low level twists:
- allows fibres to slip apart= yarn will be weak
- yarns will be thicker and rougher to the touch
- more suitable for knitting
High level twists:
- increases strength
- gives a smoother, denser yarn= more expensive
- more suitable for weaving
Brushed fabric= low level twist= so fibres can be teased apart easily to form the raised nap
Staple yarn:
What are they?
- what can be chopped to create this yarn?
- what is the surface like? what does this cause? (property)
- what kind of fabrics will they make?
- what else can these fibres do?
(2nd property)
- these yarns have more …? what does this cause it to look like? (3rd property)
Yarn made from short staple fibres that are twisted together to form a yarn
- filament fibres can be chopped into short staple fibres
- hairy= good at trapping air between fibres= good insulators
- fabrics that are warm
- can trap moisture between fibres
- more texture compared to smooth yarns= duller in appearance
Filament yarn:
What are they?
- what is the surface like? what does this mean? (property)
- what do they look like in appearance compared to staple yarns?
Yarn made by slightly twisting one or more filament fibres together
- smooth= don’t trap air between fibres= not good at insulating
- more lustrous
What is the difference between a single yarn and a plied yarn?
- what does it mean if a yarn has more plies?
- what do the plies do?
- why are single yarns twisted together in the opposite direction to the direction that they were spun? (2 reasons)
Single yarn= staple or filament fibres twisted to make one single yarn
Plied yarn= made by twisting single yarns together (e.g. 2-ply= two strands)
- more plies= more durable
- plies hold the fibres together
- yarn= even thickness & no weak spots
A fabrics weight, flexibility, handle, texture and appearance determined by?
The thickness and tightness of the yarn
How is blending achieved?
- what does this allow the fabric made to be?
- what must be done to the fibres for a successful blend? why?
e.g. what must be done to a filament fibre to be blended with a staple fibre?
- what are they mixed together in?
Spinning two or more fibres together to make a yarn
- better suited to the product
- fibres must be same length= so they can be mixed together before spun into a yarn
e.g. must be cut into a staple fibre
- different proportions needed for the yarn
What does a Monofilament yarn consist of?
A single continuous filament
What does a multifilament yarn consist of?
- what are they sometimes referred to as?
- give an example
two or more filament fibres which may or may not be twisted together
- plied yarns (folded)
- e .g. polyester & nylon
What are Core spun yarns?
- what do they consist of?
- what are the important in the manufacture of? why?
- what can the core provide if the outer fibres are weaker due to aesthetic purposes?
(Give an example of a type of core and covering fibres & what this would be used to prevent?)
Multicomponent yarns
- Core at centre of yarn covered by other fibres
- stretch yarns & sewing threads
- core provides strength (e.g. metallic yarns)
EXAMPLE:
Synthetic filament core (polyester)= strength
covering fibres (cotton)= prevent machine needle from overheating during high-speed machining
How can the characteristics of continuous filament fibres be changed?
- why is this done?
By introducing crimps, crinkles and snarls into the filaments
- done so the filament can no longer lie close to each other= able to trap air= better insulators
What are the 2 different types of yarn?
- Textured
- Fancy yarns
Fancy yarns: what do they do to fabrics?
Give texture and interesting effects
Fancy yarns: what do they have added to the length of the yarn?
Irregularities & other effects added to length of the yarn
Fancy yarns: what type of fibres can they be made from?
Any fibre
Fancy yarns: Are they made from continuous filament of staple form fibres?
BOTH
Fancy yarns: What is the most common form of a fancy yarn? (what do they have)
Have 3 different parts to the yarn
Fancy yarns: What are the 3 common parts to the yarn and how do they work? (2 steps)
- why are the threads often different thicknesses
- A fancy
- A base
- A tie thread
- fancy effect thread is twisted around a base thread
- a tie thread is then used to hold the two together
- to create the special effect
What are the 2 common types of fancy yarns?
- Slub yarn
- Chenille yarn
Fancy yarns: How is a Slub yarn usually made?
- what is the result?
- spinning thicker and thinner sections of yarn at irregular intervals
- results in yarn giving fabric a similar texture and appearance to linen or wild silk
Fancy yarns: what do Chenille yarns have?
- how is it produced?
- what is the result?
- fibres projecting from all around a central core of threads
- by weaving an open net-type fabric which is cut afterwards
- chenille fabrics are soft & bulky
Textured yarns: what are fabrics made from textured yarns like? and why?
More interesting
Textured yarns: how are these produced?
- what does this help or allow them to do?
Fine tubes created in & between textured yarns
- helps them carry water, or allows them to wick more moisture
Textured yarns: what are the properties of textured yarns?
softer= make more comfortable fabrics
- fabrics have more volume
- fabrics have less lustre
Textured yarns? what do the crinkles and snarls allow the yarn to do?
Stretch out more than an untextures yarn= more elasticity
Textured yarns: what do many of the methods used to give texture to yarns depend on?
The thermoplastic nature of the fibres= allow filaments to be heat-set into a new shape
Textured yarns: what are the 3 most important methods of texturing yarns?
- False twist
- Bulked continuous filament (BCF)
- Air-jet texturing
Textured yarns: how is a False twist yarn made?
- what is the result?
Made by twisting the yarn tightly, heat-setting it then untwisting it
- lots of crinkles and snarls
Textured yarns: how is a Bulked continuous filament (BCF) yarn made?
- what is the result?
A jet of hot fluid pushes thermoplastic yarns against a cold surface
- causes filaments to cool into a saw-tooth edge-shape
Textured yarns: how is an Air-jet texturing yarn made?
- what can this method be used with? and why?
- what are textured yarns used to make?
A jet of compress air is directed at the continuous filament yarn causes individual filaments to become tangled and create small loops along their length
- method used with any continuous filament yarn= does not depend on thermoplasticity of fibres
- sportswear, underwear, swimwear, tights
What can yarns be made from?
Staple or filament fibres
How can staple or filament fibres be manufactured & with what process?
Twists using a spinning process
What must be done to staple fibres and why?
Need to be twisted together with other fibres to make a yarn due to them being short.
What must be done to filament fibres and why?
Need to be slightly twisted with other fibres so can be made into useable yarns due to them being very fine.
What do modern fabrics contain?
More than one type of fibre
Main reasons for blending yarns: Performance properties
(4 general points)
2nd point= (cathis)= properties acronym
- make fabric stronger & more abrasion resistant
- make fabric easier to care for (less prone to shrinking & creasing)
- improve comfort, absorbency, thermal insulation & stretch
- to give thermoplastic properties to enable heat-setting
Main reasons for blending yarns: Aesthetic appearance (3 general points)
- Improve texture & handle of fabric
- Give novelty effects especially when yarn or fabric is dyed (e.g. uptake of dye by some fibres better than others)
- To give improved colour or lustre
Main reasons for blending yarns: Additional advances (2 points)
- Reduces costs if a cheaper fibre is included
- allows for quicker washing and drying times (beneficial to environment)
Main reasons for blending yarns: Additional disadvantages
- give an example of a blend that may cause a problem
- explain why
Polyester/Cotton blend= burn fiercely at high temps & give off toxic fumes
Cotton= sets alight very easily, holds polyester in place which then melts and drips= causing severe burns
