An Investigation on the Progressive Change in Filament Characteristics from Outer to Inner Layers of Mulberry and Tasar Cocoons

The physical properties and residual sericin content of the silk filament were evaluated in relation to its position in different layers of the cocoons corresponding to Daba (Antheraea mylitta), oak tasar (Antheraea proylei), and bivoltine mulberry (Bombyx mori) varieties. A decrease in filament linear density from the outer to the innermost layers was observed in all the varieties. Although the filament tenacity was found to increase in bivoltine mulberry cocoons from the outer to the inner layers, no such specific trend was observed for Daba cocoons. For oak tasar cocoons, it showed a marginal rise. A similar trend was observed for filament initial modulus also. The breaking extension of filament was constant for Daba cocoons, decreased for oak tasar cocoons and showed a rise followed by a fall for bivoltine mulberry cocoons from the first to the last layers. The residual sericin decreased marginally from the outer to the inner layer in the case of tasar cocoons. However, for mulberry cocoons it decreased rapidly initially up to the fourth layer and thereafter showed no change. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010