lec 22 Flashcards
why are plant fibres so strong?
cellulose, which is linear chains of glucose that make the plant cell wall
cotton fibres. how much of it is cellulose?
the purest natural form of cellulose, containing more than 90% cellulose by weight
where was the earliest evidence of cotton use?
present day pakistan, 5500 BCE (tree cotton aka Gossypium arboretum)
what cotton do we use mostly today?
Gossypium hirsutum aka upland cotton
what are some traits of cotton as a plant?
cotton fruit is a capsule, with simple dry dehiscent fruit(split open when ripe), with two or more carpels
what are some traits of cotton as a textile?
breathable, highly moisture wicking, decently heat retentive and stretchable, high in pilling
what is the cotton harvesting/processing process? how much cotton is needed to make one shirt?
- defoliation: in the field, cotton plants are sprayed with a defoliant that removes leaves
- machine harvesting: it all gets harvested up
- cotton gin: a cotton gin separates cotton seeds from the bolls, and removes dirt and contaminants
- carding: cotton is spun into long strands
- spinning: strands are spun to make yarn
- dyeing: cotton yarn is treated w chem, then dyed
- weaving
1 shirt = 1.8 yards of fabric = 57 miles of yarn = 350 cotton bolls
what is the oldest textile used by humans?
flax
what makes flax so good?
2 to 3 times stronger than cotton fibres
where was flax first domesticated
humans first domesticated flax in the fertile crescent around 7000 BCE
in china and india, domesticated flax was around at least 3000 BCE
we also know egypt been used flax
how is flax harvested? prepared? processed?
either the entire plant is pulled up, or its cut close to the root
plants are then dried and seeds are threshed
to process, fibres must be loosened from the stalk via retting, which uses a bacteria to decompose the pectin (thing that keeps fibres bound)
then its put in metal rollers that separates the stalks out
benefits/harms of using chemical retting?
+ more efficient
- hurts flax fibres
- hurts environment
which do we use more today: cotton or linen?
cotton, largely because it was more economically rational (slave labour…)
how long ago did we start using plant dyes>
about 3000 CBE
why have we switched to chem dyes?
aniline dyes are:
+ more easily transferred
+ don’t take as much prep time (quicker to make than extracting)
+ stand up better to washing and exposure to sunlight
