STUDY OF PROPERTY & STRUCTURAL VARIANTS OF MULBERRY AND TASAR SILK FILAMENTS

The tensile behaviour of fully degummed filaments of two commercial varieties of silk produced in India, namely mulberry (Bombyx mori) and tasar (Antheraea mylitta), has been investigated in dry and wet state. The tensile properties were correlated with the structures and morphologies of these two varieties of silk. The tenacity and elongation at break of these silks were not significantly different in dry and wet state; however, a slight reduction in initial modulus was noticed in wet state. The stress-strain behaviour of mulberry silk filament was different from that of tasar in that it demonstrated a characteristic yield point, lower modulus and elongation at break twice as high as that of mulberry. The characteristic stress-strain behaviour of theses two varieties of silk was correlated with density, birefringence, orientation index, sonic modulus and amino-acid composition. Poor orientation and less order in tasar are related to the higher percent of bulky groups present in fibroin.