Tuesday Lecture – Fibers and Dyes

Tuesday Lecture – Fibers and Dyes Reading: Textbook, Chapter 15

Collect assignments – plant-derived chemicals added to food products

Fibers - History Use of plant fibers seems to predate that of animal fibers Note: relatively few plants or animals produce fibers that can be woven or spun – use seems fairly recent Fig. 15.1, p. 556

Fibers - History Use of plant fibers seems to predate that of animal fibers Note: relatively few plants or animals produce fibers that can be woven or spun – use seems fairly recent 10,000 yrs ago – linen (from Linum) in Turkey Fig. 15.1, p. 556

Fibers - History Use of plant fibers seems to predate that of animal fibers Note: relatively few plants or animals produce fibers that can be woven or spun – use seems fairly recent 10,000 yrs ago – linen (from Linum) in Turkey 8,000 yrs ago – fiber sandals in Missouri Fig. 15.1, p. 556

Fibers - History Use of plant fibers seems to predate that of animal fibers Note: relatively few plants or animals produce fibers that can be woven or spun – use seems fairly recent 10,000 yrs ago – linen (from Linum) in Turkey 8,000 yrs ago – fiber sandals in Missouri 7,000 yrs ago – sheep domesticated Fig. 15.1, p. 556

Fibers - History Use of plant fibers seems to predate that of animal fibers Note: relatively few plants or animals produce fibers that can be woven or spun – use seems fairly recent 10,000 yrs ago – linen (from Linum) in Turkey 8,000 yrs ago – fiber sandals in Missouri 7,000 yrs ago – sheep domesticated 5,400 yrs ago – cotton fibers used in Mexico Fig. 15.1, p. 556

Fibers - History Use of plant fibers seems to predate that of animal fibers Note: relatively few plants or animals produce fibers that can be woven or spun – use seems fairly recent 10,000 yrs ago – linen (from Linum) in Turkey 8,000 yrs ago – fiber sandals in Missouri 7,000 yrs ago – sheep domesticated 5,400 yrs ago – cotton fibers used in Mexico 5,000 yrs ago – silk in Asia Fig. 15.1, p. 556

Plant vs. Animal Fibers • Plant fibers: composed – partly - of cellulose • Animal fibers: composed of protein molecules Fig. 15.2, p. 557

Plant vs. Animal Fibers • Plant fibers: composed – partly - of cellulose • can be heated • hard to dye • attacked by fungi, mold, termites • less elastic but more absorbent of water • Animal fibers: composed of protein molecules • denatured by heat  brittle Fig. 15.2, p. 557

Plant vs. Animal Fibers • Plant fibers: composed – partly - of cellulose • can be heated • hard to dye • attacked by fungi, mold, termites • less elastic but more absorbent of water • Animal fibers: composed of protein molecules • denatured by heat  brittle • readily accept dyes Fig. 15.2, p. 557

Plant vs. Animal Fibers • Plant fibers: composed – partly - of cellulose • can be heated • hard to dye • attacked by fungi, mold, termites • less elastic but more absorbent of water • Animal fibers: composed of protein molecules • denatured by heat  brittle • readily accept dyes • attacked by moths, silverfish Fig. 15.2, p. 557

Plant vs. Animal Fibers • Plant fibers: composed – partly - of cellulose • can be heated • hard to dye • attacked by fungi, mold, termites • less elastic but more absorbent of water • Animal fibers: composed of protein molecules • denatured by heat  brittle • readily accept dyes • attacked by moths, silverfish • more elastic, less absorbent of water Fig. 15.2, p. 557

Classification of Fibers • Seed/Fruit Fibers – aid in seed dispersal • cotton, coir, kapok • Bast Fibers – from phloem of stem • hemp, jute, ramie, linen • Hard Fibers – from leaves of monocots • - sisal, henequen, Manila hemp Material % Cellulose Cotton 98 Ramie 86 Hemp 65 Jute 58 Deciduous woods 41-42 Coniferous woods 41-44 Cornstalks 43 Wheat straw 42

Fiber Extraction Seed Fibers (Cotton) – actually trichomes, not fibers Ginning – separates fibers from seeds Mostly Bast Fibers: Retting – rots away non-fiber parts Scutching – beat and scraping retted plant material to remove broken pieces of woody matter Hackling – drawing a mass of fibers across pins to separate and align fibers Leaf Fibers Decorticating – crushing plant material and scraping away the nonfibrous material

Fig. 15.7, p. 562 Seed Fibers - Cotton

Cotton – Ancient History Fig. 15.9, p. 564 4 independent domestications of cotton Problem: New World domesticates – have one genome present in wild only in Old World Possible resolution: AA genome predates continental separation G. arboreum G. hirsutum Diploids AA Tetraploids AADD G. herbaceum G. barbadense

Cotton – More Recent History Hand Labor – Associated with Slavery in U.S. Fig. 15.11, p. 565 Cotton Gin – Enhanced Value

Cotton - Spinning

Cotton - Today Cotton – Issues: Chemical Use Irrigation

Cotton Cloth - Details Cleaning – boiling in caustic soda, then treat with hydrogen peroxide  removes pectins, waxes; lightens color of fibers Mercerizing (invented by J. Mercer) – soak thread or textile under pressure in caustic soda  fibers swell, change shape Sizing – add starch or gel to thread, fills in irregularities, strengthens Sanforization – ammonia process, swells fibers and prevents shrinking Permanent press – use chemicals to cross-link cellulose polymers  garment retains shape even after washing

Dye Plants Paradox: We associate plants with beautiful colors, yet most plant pigments do not make good dyes

Dye Plants Paradox: We associate plants with beautiful colors, yet most plant pigments do not make good dyes Resolution: Most plant pigments are chemically instable – when removed from the environment of the plant cell they are quickly degraded or washed away

Dye Plants • Paradox: We associate plants with beautiful colors, yet most plant pigments do not make good dyes • Resolution: Most plant pigments are chemically instable – when removed from the environment of the plant cell they are quickly degraded or washed away • Plant Dyes: • must be chemically stable (many oxidize when exposed to air) • must bind to object being dyed (=fastness) • Mordant: chemical that increases adherence of dye to fabric • - may also change color of dye

Reminder This Thursday, April 21 – class will meet at UT Institute of Agriculture Gardens, next to the Vet School. Dress appropriately to be outside and take a garden tour.

Tuesday Lecture – Fibers and Dyes