Chapter 6-1

Chapter 6-1 - Chapter 6 – Manufactured Cellulosic Fibers...

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Unformatted text preview: Chapter 6 – Manufactured Cellulosic Fibers: Rayon: – 1 st regenerated fiber – artificial silk – 1 st commonly produced in US – named rayon – first manufactured fiber composed of regenerated cellulose – unmodified cellulosic fiber Unmodified cellulosic fibers • viscose rayon • regular rayon • high-wet-modulus rayon HWM • high tenacity rayon cuprammonium rayon • lyocell (the youngest member) Modified cellulosic fibers (modified chemically from nature) • acetate • triacetate Viscose Rayon: • wood pulp • major source • cotton fibers • linters bamboo goes through same process as viscose rayon • timber harvested • eucalyptus tree • spruce tree • southern pine • chips treated • to remove lignin & resin • dissolving pulp • 95% cellulose • pressed into blotter-like sheets (which are 95% cellulosic) Manufacturing Steps of Viscose Rayon: 1. slurrying ( steeping ) – soaked in sodium hydroxide – alkali cellulose – shredded into “white crumbs” 2. ageing – polymer chains broken – easier to dissolve 3. xanthation – carbon disulfide – polymers pushed apart – orange-yellow material 4. dissolving & ripening – in sodium hydroxide – viscous like honey 5. filtration – insoluble particles removed – delustering agent, pigment added 6. extrusion – wet spun • dilute sulfuric acid bath Rayon is an extremely non-environmental friendly to produce, it is not longer produced in US, but it used in Asia Modifications: • High-Wet-Modulus rayon (HWM) – modal, polynosic rayon – resistance to deformation when wet – not aged, xanthate dissolved in water, lower acid concentration, stretched more • high-tenacity rayon – tire cords • outer cores that have a thicker skin • cellulosic like cotton regular viscose rayon – short chains – much lower dp – lower orientation – smaller crystalline/higher amorphous areas – most used rayon today and this rayon’s are not durable HWM rayon Longer chains More crystalline Low dp Physical Properties: • color & luster – white – bright or dull with a delusterant and you can see little dots • shape – regular rayon serrated/striations – HWM less crenulated • specific gravity – moderate – like cotton, linen (burn like cotton, because they are cellulosic) Mechanical Properties: • strength – lower than cotton, linen • no fibral structure • more amorphous inner structure – decreased wet strength – HWM better • modulus – HWM similar to cotton, polyester • Blends-“modale” is the French word for High wet modulus • elongation & recovery – viscose rayon will stretch with low elastic recovery • resilience – low – wrinkle resistant finishes weaken fiber Chemical Properties: •...
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This note was uploaded on 01/19/2012 for the course HUEC 2040 taught by Professor Staff during the Fall '08 term at LSU.

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Chapter 6-1 - Chapter 6 – Manufactured Cellulosic Fibers...

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