纺织材料的英文版系列文件(6个ppt)9.ppt

1、Chapter 11 Silk Fibers,Yiping Qiu,Introduction,The larva of certain insects for use in their building webs, climbing ropes and cocoons Spiders Commercial silk industry: use larva of silkworm Application: Mostly apparel, was also used for parachutes.,Structure,Macrostructure: Length: 1000-1300 yds (9

2、15-1190 m)/cocoon Max 3000yds (2750m)/cocoon, 1 fiber/cocoon. Thickness: 9-11 mm or 1.2-1.5 denier. Varies: thickest in the middle thinnest inside (maybe running out of raw material, or maybe just make itself comfortable).,Structure,Microstructure cross-section: 2 triangular filaments co-extruded by

3、 a worm. The two are called brins held together by sericin (gum or silk glue). Wild silk worms produce ribbon-like silk fibers,Structure,Submicrostructure Silk from cultivated worm: no identifiable submicrostructure. Wild silk or Tussah silk has internal fibrillar structure.,Structure,Fibroin protei

4、n polymer A chain of amino acids forming a protein called fibroin composed of 15-18 different amino acids. Glycine, alanine and serine occupy 86% of the polymer The side groups of the above 3 amino acids are small compared with those in wool: glycine: R = H alanine: R = -CH3 Serine: R = -CH2OH Cryst

5、allize readily: 70-75%,Structure,Fibroin protein polymer Pack well: lots of H-bonds, small number of ionic bonds No cystine: no S-S bonds Configuration: pleated b-sheet Degree of polymerization of silk DPsilk DPwool,Properties,For silk producers, i.e. silk worm, spider etc., silk fibers are for prot

6、ection, transport and food capture Mechanical properties Medium tenacity but higher than wool resulted from molecular structure: zigzag b-sheet of silk vs a-helix of wool higher crystallinity than wool,Properties,Mechanical properties Medium elongation at break High elastic recovery at low elongatio

7、n When elongated 2%, 90% elastic recovery Medium modulus Medium abrasion resistance Medium resilience: (cotton silk wool) pleated sheets can slide over one-another.,Properties,Comfort High heat of wetting: lots of polar groups available High water absorption: up to 1/3 of its weight Smooth and soft

8、High luster: high crystallinity and triangular cross-sectional shape. Scroop: rustling sound due to an acid treatment that hardens fiber surface.,Properties,Other properties Ignites and burns but sometimes selfextinguishing Dry-cleaning preferred due to: lower tenacity and initial modulus when wet d

9、egraded by alkaline solutions may be hand-washed using mild detergents Lowest UV light resistance: avoid prolonged exposure to sunshine,Production,Moth: Bombyx fed on mulberry tree leaves World production: 145.5 million lbs/yr Originally from China Types: Raw silk: silk with gum Tussah: wild silk Du

10、ppioni: 2 silk worm spin their cocoons together: having special appearance similar to wild silk but better color,Chapter 12 Cotton Fibers,TMS211 Yiping Qiu,Introduction,Cotton: seed hair obtained from the boll of the cotton plant 4000 fibers/seed, max 20,000 fibers/seed 250,000 fibers/boll Types: Co

11、mmodity: Upland Long staple: Pima-Su Pima Sea island Egyptian Other: naturally colored,Introduction,Application: 55% of apparel fibers are cotton 70% of mens apparels made of cotton 40% of womens apparels made of cotton 65% of all cotton fibers were used for apparels in 1990 Additional 27% of cotton

12、 for sheets and towels or other non-apparel household applications 7% for industrial use,Structure,Cotton fiber: single plant cell Macrostructure Staple length: 1/8” - 2.5” (0.32 - 6.35 cm) Cotton fibers used in textile yarns: 7/8” - 1.25” Diameters: 16 - 20 mm but varies from fiber to fiber: longer

13、 fibers are finer Length to breadth ratio: 6000:1 to 350:1 Relatively uniform along its length Color: never truly white but creamy white to gray,Structure,Microstructure Flat, twisted ribbon 125 twists/inch (convolutions) The twists reverse in direction along the length Cross-section: kidney-bean sh

14、aped with a lumen,Structure,Submicrostructure 5 distinctive regions: Cuticle: out layer of wax, a few molecules thick to protect seeds but can be removed by wet processing and laundering. Primary wall: composed of fibrils: a sheath of spiraling fibrils 20 - 30 degree to the fiber axis Mature fibers

15、- thicker primary walls; immature fibers thinner primary walls and entangles: forming clumps called neps: leading to nonuniform dye properties and irregular surface of fabrics,Structure,Submicrostructure 5 distinctive regions: Secondary wall: bulk of the fiber concentric layer of spiraling fibrils s

16、imilar to rings of trees 20 rings and each corresponding to 1 days growth. outmost layer of secondary wall: winding layer Lumen: hollow canal running through the length of the fiber,Structure,Polymer system Linear cellulose Average Degree of Polymerization 6,000 to 10,000 Functional side group: -OH

17、Crystallinity: 65 - 70% but depends on how to define. H-bonding sites: not -OH to -OH but OH to the O group between the neighboring two rings: confers strength and additional rigidity to the fiber. -OH: reacting with a variety of chemicals: thus finish can be applied easily, also attract and hold wa

18、ter.,Structure,Polymer system -C-O-C- bonds are more susceptible to oxidation than C-C-C bonds 20 41% unoccupied space, 1/3 by lumen,Properties,Mechanical Properties Tenacity and initial modulus: medium Elongation at break: low: spiral fibrils: makes it relatively brittle Elastic recovery: low, only

19、 75% at 2% extension: due to H-bond,Properties,Comfort Fiber ends and convolutions: comfortable to touch Hydrophilic: max water absorption: 25-27% regain due to -OH group and fibrils Upon water absorption, fibers become softer and collapses on to skin, dries slowly When it is dry: comfortable becaus

20、e of water absorption, water vapor transfer and no static charge,Properties,Comfort Water resistant fabric possible: swelling of fibers in water: no liquid water penetration Maintenance Soiling: easy to be soiled and desoiled due to -OH groups Launderability: dimensionally stable and tenacity increa

21、ses when wet (10-20%) due to improvement of fibril orientation and thus molecular orientation.,Properties,Maintenance No special precautions for laundering, high temperature, any detergents, and bleaches can be used. Shrinkage likely due to relaxation of yarn tension induced by processing,Properties

22、,Other properties acids cause degradation of cotton or cellulose: acid free paper for long lasting items not affected by most of organic solvents damaged by fungi and bacteria prolonged exposure to sunlight: yellow heat resistant low luster high cover power,Properties,Other properties no pill but li

23、nt highly flammable and can smolder without fire for hours: need flame-retardant treatment for many end uses biodegradable can be boiled and sterilized: good for hospital use,Mercerized cotton,Process:(applied to either fibers or yarns) cold bath of 18-27% NaOH for 1 minute or less rinsed and neutra

24、lized by a cold acid bath tension applied to break H-bonds polymer rearranged and reoriented: untwist rounder cross-section and the convolutions are nearly gone Stronger, more lustrous and easier to dye,Chapter 14 Rayon,TMS 211 Yiping Qiu,Introduction,Rayon: ray of light on Invented 1884 Definition:

25、 manufactured fibers composed of 100% regenerated cellulose, as well as manufactured fibers of regenerated cellulose in which substituents have replaced not more than 15% of the hydrogens of the -OH groups.,Introduction,Made from 4 processes: Nitro cellulose: made in U.S. during 20s-40s and easy to

26、explode. Viscose: 95% today spun in U.S. Cuprammonium: use cuprammonium hydroxide solvent as spinning solution Lyocell,Introduction, 4% of total fiber consumed in the U.S. Usage: 52.4% apparels 26.8% nonwovens 20.8% households,Structures,Macrostructure Continuous filaments or staple: 1.5-15 denier M

27、icrostructure: Surface: striated Cross-section: serrated Submicrostructure Skin-core structure: caused by spinning process Skin: small crystal, imperfect, darker Core: large, more perfect crystal,Structures,Molecular Regular viscose rayon: DP400 (cotton 6k-10k) 35 - 40% amorphous,Properties,Mechanic

28、al Medium tenacity and elongation Low initial modulus Low elastic recovery Low bending rigidity Tenacity and modulus drops drastically upon water absorption: -50%. Elongation to failure +20%.,Properties,Comfort Hydrophilic and high moisture regain: 13% at 70% RH: more absorbent than cotton due to more amorphous region. High heat of wetting High cross-sectional swelling Irregular surface next to ski