Crystallinity in silk fibers: Partial acid hydrolysis and related studies

Four Indian varieties of silk viz., Mulberry, Tasar, Eri, and Muga, have been investigated by x-ray diffraction and infrared spectroscopy. The hydrolysis for Mulberry was carried out using 6N HCI at 40°C, whereas the other wild varieties of silk were hydrolyzed partially using 8N HCI at 40°C. The x-ray order factor, IR crystallinity index, and crystallite size have been determined for control, 48-hr hydrolysates, and (48 + 48)-hr hydrolysates. The lateral order improvement need not be associated with selective dissolution of amorphous region. This was further varified by short duration hydrolysis. A sort of recrystallization process could be attributed to order improvement. The results are discussed to understand the fine structure of the crystalline region of the fibroin.