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Chapter 7

Textiles - Chapter 7.docx

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Ryerson University
FSN 101
Sandra Tullio Pow

Chapter 7: Manufactured Regenerated Fibres p 132-147 - Manufactured regenerated fibres are produced from naturally occurring polymers of cellulose or protein but processing is needed to convert them into fibre form Cellulosic Regenerated Fibres Rayon - First regenerated cellulosic fibre and many processes were developed - Commercial production of rayon began and it was sold as artificial silk until rayon was adapted - Viscose filament fibre; original form, was a brightly lustrous fibre; rayon was discovered when a textile worker discovered that broken waste rayon filament could be used as a staple fibre - Early rayon fabrics: transparent velvet, sharkskin, tweed, challis, chiffon - Regular rayon produced in US is viscose rayon - Zinc added to spinning bath slowed polymer regeneration  increasing crystallinity - High-wet-modulus rayon has different characteristics – (viscose rayon is weaker fibre) - HWM is also high performance rayon (polynosic rayon or modal) - Production not expected to increase because high cost of replacement of machines and wet spinning; it is now as much as cotton Production of Rayon - Wet spinning is most common method for rayon; purified cellulose converted to viscous solution then forced through spinneret to a bath and return to cellulose filament - Process differences produce fibres with different properties (viscous rayon) Physical Structure of Rayon - Characterized by lengthwise lines called striations – cross section is indented circular shape that develops from loss of solvent during thickening and following collapse of the cross section – advantage for dyeing it increases fibre’s surface area - Rayon fibres are naturally bright which limits use to formal apparel; can deluster the pigment - 100% cellulose and same chemical composition as cotton but less crystalline - Does not have cellular structure in a natural fibre; cellulose from wood pulp breaks down aging steps in rayon so shortens the polymer chains - Stretching aligns molecules to give strength - Since acid bath is less concentrated > slower regeneration to achieve stretch and orientation Properties of Rayon - Highly absorbent, soft, comfortable, easy to dye, versatile; unique soft drape that designers desire Aesthetics - Luster, length and diameter can be controlled, it can be made into fabrics that resemble cotton, linen, wool, silk  engineered with physical characteristics - Attractive soft fluid drape, sizing may be added to increase hand Durability - Regular rayon is weak that loses 50% of its strength when wet - Lowest elastic recovery; does not recover well when stress is removed  amorphous regions in fibre - Water enters amorphous areas causing molecular chains to separate, breaking hydrogen bonds and distorting chains > water is removed but new hydrogen bonds are formed but distorted - HWM has more crystalline so the dry fibre is relatively strong Comfort - Comfortable, smooth soft fabric good for the skin; absorbent and eliminates static - Good for warm weather but not for cold weather wear Appearance Retention - Resiliency is low; HWM can be improved by adding wrinkle-resistant finish but loss of strength and abrasion resistance - Fabrics may shrink/stretch with low elastic recovery but less likely to stretch out of shape Care - Limited wash ability because of their low strength when wet – tendency to shrink progressively; most should be dry cleaned – increase fabric body - HWM have greater wash ability – equal to cotton; wrinkles less than regular rayon in washing and drying - Lack of label in interior textiles make it difficult; rarely distinguish between HWM and regular  cleaned when necessary - Harmed by acids, damaged by silverfish and mildew, somewhat sunlight resistant Environmental Concerns and Sustainability of Rayon - Most are produced from wood pulp from fast-growing softwood trees; some are harvest located on marginal agricultural land  cut from mature forests - Issues related to clear-cut with no habitats for animals - Processing wood pulp uses large quantities of acid and other chemicals that contribute to water and air pollution - Process air emissions of high pollution – water is low in dissolved oxygen creates problem for aquatic life - Biodegradable – not generally recycled since it is used in sanitary products (diapers) - Dry cleaning which adds hazards to the environment Uses of Rayon - Woven fabrics; draperies; when absorbency is important- medical supplies like bandages, diapers Types and Kinds of Rayon - Only way to determine type is by trade name; but is used as a marketing tool with consumers Lyocell - Was developed because of rayon’s negative environmental impact Production of Lyocell - Wet spinning is used; dissolved into liquid and spun into a weak bath of amine oxide  solvent with low toxicity and skin irritation without changing nature of cellulose Physical Structure of Lyocell - Does not collapse on itself and has rounded cross section and smoother longitudinal appearance - Available in variety of deniers, lengths, filaments per yarn - 100% cellulose with same chemical composition in natural cellulose - Polymer chain length is longer than rayon but not as cotton; drawing fibres after spinning +orientation = more durable Properties of Lyocell - More like cotton; soft, flowing drape Durability - Performs more like cotton; strongest of cellulosic fibres – only 12% loss in strength when wet - Soft hand and durability = comfortable and long lasting apparel and interior - Application that require high wet strength are ideal - Abraded = fibrillate (split lengthwise) produced fuzzy texture Comfort - Soft, smooth; not many problems with static, ideal for apparel that comes
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