广东纺织职业技术学院：《纺织材料学》课程教学资源（PPT课件，英文版）4 Silk Fibers

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Chapter 11 Silk Fibers

Chapter 11 Silk Fibers

广东费织职业故术学院 Guangdong Inatitute of Textile Technology Introduction a The larva of certain insects for use in their building webs, climbing ropes and cocoons 口 Spiders a Commercial silk indust ry: use larva of silkworm a Application Mostly apparel, was also used for parachutes

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

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Structure Macrostructure Length 1000-1300 yds(915-1190 m)/cocoon Max 3000yds(2750m)/cocoon 1 fiber/cocoon ■ Thickness: a 9-11 um or 1.2-1.5 denier 口∨ aries: thickest in the midd| e thinnest inside(maybe running out of raw material or maybe just make itself comfortable)

Structure  Macrostructure: ◼ Length: 1000-1300 yds (915-1190 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)

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Structure a Microstructure cross-section 2 triangular filaments co- extruded by a worm The two are called brins held together by sericin(gum or silk glue) Wild silk worms produce ribbon-like silk fibers

Structure  Microstructure ◼ cross-section: 2 triangular filaments co￾extruded by a worm. ◼ The two are called brins held together by sericin (gum or silk glue). ◼ Wild silk worms produce ribbon-like silk fibers

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Structure 口 Submicrostructure silk from cultivated worm i no identifiable submicrostructure wild silk or tussah silk has internal fibrillar structure

Structure  Submicrostructure ◼ Silk from cultivated worm: no identifiable submicrostructure. ◼ Wild silk or Tussah silk has internal fibrillar structure

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Structure Fibroin protein 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 日 glycine:R=H 口 alanin e:r=-cha 口 Serine:R=-CH2OH Crystallize readily:70-75%

Structure  Fibroin protein 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 ◼ Crystallize readily: 70-75%

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Structure Fibroin protein polymer Pack well lots of h bonds small number of ionic bonds No cystine: no s-S bonds ■ Configuration: pleatedβ- sheet Degree of polymerization of silk dPsilk dpwool

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

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Properties a For silk producers, i.e. silk worm spider etc, silk fibers are for protection transport and food capture 日 Mechanical properties Medium tena city but higher than wool d resulted from molecular structure ■ Zigzagβ- sheet of silk ys ahel× of wool higher crystallinity than wool

Properties  For silk producers, i.e. silk worm, spider etc., silk fibers are for protection, 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

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Properties a Mechanical properties Medium elongation at break High elastic recovery at low elongation When elongated 2/6, 90% elastic recover ■ Medium modulus Medium abrasion resistance Medium resilience :(cotton silk wool) pleated sheets can slide over one- another

Properties  Mechanical properties ◼ Medium elongation at break ◼ High elastic recovery at low elongation When elongated 2%, 90% elastic recovery ◼ Medium modulus ◼ Medium abrasion resistance ◼ Medium resilience: (cotton < silk < wool) pleated sheets can slide over one￾another

广东费飘职业故本学院 Guangdong Inatitute of Textile Technology Properties 口 Comfort high heat of wetting: lots of polar groups available High water absorption up to 1 3 of its weight ■ Smooth and soft High luster: high crystallinity and triangular cross-sectional shape Scroop: rustling sound due to an acid treatment that hardens fiber surface

Properties  Comfort ◼ High heat of wetting: lots of polar groups available ◼ High water absorption: up to 1/3 of its weight ◼ Smooth and soft ◼ High luster: high crystallinity and triangular cross-sectional shape. ◼ Scroop: rustling sound due to an acid treatment that hardens fiber surface