CHEMICAL-STRUCTURE AND PHYSICAL-PROPERTIES OF ANTHERAEA-ASSAMA SILK

This work deals with the chemical composition, physical structure, and thermal behavior of Antheraea assama silk fibers. The amino acid comp osition is characterized by the high content of alanine, glycine, and serine. Among the amino acid residues with polar side chains, aspartic acid, arginine, and tyrosine prevail. The birefringence and isotropic refractive index values are 0.030 and 1.557, respectively. The stress -strain curve shows a yield point at 5% elongation, followed by a regi on of gradual extensibility. Elongation at break is about 40%. The X-r ay diffraction pattern is typical of beta silks, with - (ala)n- repeat s in the polypeptide sequences of the crystalline regions. The differe ntial scanning calorimetry curve shows two minor endotherms at 230 and 300-degrees-C, before final thermal decomposition at 362-degrees-C. T he maximum extent of contraction exhibited by the thermomechanical ana lysis curve is 2%. The surface of degummed fibers shows the presence o f longitudinal striations. The fiber cross section is mostly elliptica l. Raw fibers taken from cocoons show the presence of several crystall ine deposits on the surface, identified as crystals of calcium oxalate . (C) 1994 John Wiley & Sons, Inc.