UV DEGRADATION OF BIVOLTINE SILK FIBER: A POSITRON ANNIHILATION STUDY

The effects of ultra-violet (UV) irradiation on the microstructure of semicrystalline bivoltine silk fibers have been investigated using the positron annihilation lifetime (PAL) technique. Lifetime results indicate that in the early stages of UV irradiation, chain scission leads to free radicals formation. Cross-linking is the main process at longer radiation time to UV. Present results also show that silk-I type with a low degree of molecular orientation changes to silk-II type on UV irradiation.