Ultrasonics induced variations in molecular structure and tensile properties of silk fibers in a chemical free environment

Ultrasonics can be used as an alternative energy supply for a green silk wet processing and for enhancement of some chemical/physical properties of bio‐polymers. In this work, ultrasonically treated silk fabric were compared with that of untreated and were investigated for the changes in fiber conformation structure and subsequent tensile property. Experiments were conducted under different time duration in a chemical free environment. Fiber surface energy distribution and transformation of silk secondary structure were analyzed using X‐ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectrum (FITR). Results showed that subject to treatment time, a surface oxidation effect and a light transformation of random coil to β‐sheet can be induced from ultrasonic irradiation. Tensile testing showed that under certain treatment time, ultrasonics can lead to silk fibers with a slightly increased strength and reduced extensibility, as a result of the transition of fiber secondary structure. Subject to ultrasonic treatment time, a surface oxidation effect and a light transformation of random coil to β‐sheet of silk structure can be induced from the ultrasonic irradiation. This transition of fibre secondary structure may also lead to silk fibres with a slightly increased strength and reduced extensibility.