Thermal properties of Bombyx mori silk fibers

Abstract

ABSTRACT:The thermal properties of Bombyx mori silk fibers subjected to heat treatment were examined by thermogravimetry, differential thermal analysis, Fourier transform infrared absorption spectrometry (TG-DTA-FTIR) and scanning electron microscopy (SEM). The color, size, and shape of B. mori cocoon shells were observed as they were heated from 25 to 550°C. Only 1% of the original cocoon shell weight remains as cocoon ash after treatment at 550°C. Inorganic components, such as calcium, potassium, sulfur, magnesium, etc., were detected in the cocoon ash by energy dispersion fluorescent X-ray spectrometry. A sharp decrease in weight was observed in the TG data beginning around 280°C, and an endothermic peak appeared at 308°C, as evidenced by the DTA curves. The IR bands observed at 2380 cm Ϫ1 (OOH stretching), 1760 cm Ϫ1 (CAO stretching), 1503 (NOH stretching), 1085 cm Ϫ1 (CON stretching) and 965 cm Ϫ1 (ONH 2 stretching) become stronger as an exothermic reaction beginning at 280°C takes place. This is probably due to cleavage of the main chain and the accompanying decomposition of the silk fibers. Similarly, a SEM micrograph of silk fibers treated at 300°C shows a microtubule in the middle of the silk fibers of about 25-m diameter. This suggests that the thermal reactions starts in the middle of the silk fiber and forms a microtubule.

Surface Functionalization of “Rajshahi Silk” Using Green Silver Nanoparticles

“…Figure 5A, (a), (b), and (c) illustrate the TGA curves of the control (untreated) and the Ag nanoparticles (35 ppm and 70 ppm, respectively) treated silk samples, with two peak temperatures and three successive stages of weight loss. The initial weight loss of the control and AgNPs-treated samples came to about 5.5% and 4.5%, respectively, until about 198 • C. As stated previously, these weight changes could be explained by the removal of adsorbed water [37]. Due to the hydrophilic nature of silk, it was subjected to a dehydration process, in which absorbed or crystal water was removed, and the color turned yellow.…”

“…The initial weight loss of the control and AgNPs-treated samples came to about 5.5% and 4.5%, respectively, until about 198 °C. As stated previously, these weight changes could be explained by the removal of adsorbed water [37]. Due to the hydrophilic nature of silk, it was subjected to a dehydration process, in which absorbed or crystal water was removed, and the color turned yellow.…”

Surface Morphology and Properties of Bombyx mori Silk Fibroin Fiber Treated with I 2-KI Aqueous Solution

“…Fibroin is known to form mainly three kinds of conformations: silk I with a helical conformation, silk II with an antiparallel -sheet, and a random coil without definite orders. Sericin, which comprises approximately 25wt% of the silkworm cocoon, contains glycine, serine, and aspartic acid totaling over 60% of the overall composition [4][5].…”

Structure and properties of cocoons and silk fibers produced by Hyalophora cecropia

“…This difference in the thermal behavior of cecropia silk compared to B. mori silk should mainly be due Data for B. mori and wild silks are from references [1][2][3] to the differences in the composition of the two fibers. Considerable changes in the color of the cocoons from yellow to black to white are reported to occur when B. mori cocoons were heated from 190 to 550 °C for various periods of time [30].…”