Silk
fibroin, a biodegradable component of silk, is increasingly
used for various applications and studied intensively. Recently, a
technique for preparing nanofibers without using chemicals has been
gaining attention from the environmental impact and safety perspectives.
This study focuses on the structure observation of ground silk fibroin
(GF) prepared using a grinding method, which is a physical nanofibrillation
method. The fabricated nanofiber samples were examined in detail using
the X-ray diffraction (XRD), differential scanning calorimetry (DSC),
micro Raman spectroscopy, and atomic force microscopy (AFM) techniques.
The nanofibrillated structures were observed in both GF and regenerated
silk fibroin (RF) samples prepared using the conventional method.
As results, AFM images showed that the nanofibril diameter of GF was
about 1.64 nm and that of RF was about 0.32 nm. Methanol treatment
induced a structural transition from a random coil to a β-sheet
for the RF film, but it had no effect on the GF film. Thus, it is
suggested that the grinding method provides not only ultrafine silk
fibroin nanofibers without using toxic reagents but also resistance
to reagents such as methanol.
The sap of urushi tree (Toxicodendron vernicifluum (Stokes) F.A. Barkley) has been used for coating materials and is known as urushi or oriental lacquer in East Asia. The potential of termite attacks against wood samples coated with four types of urushi: Ki-urushi, Sugurome-urushi, Kuro-Sugurome-urushi, and Bengara-urushi, in correlation with their chemical and mechanical properties was investigated in this study. Mortalities of the subterranean Formosan termite (Coptotermes formosanus Shiraki) after a 3-week no-choice feeding tests in samples coated with all types of urushi showed no significant difference from those of control samples. However, mass loss of the sample coated with urushi was lower than that of the control sample especially for Sugurome-urushi (Tukey's test: p < 0.05). Results of Fourier transform infrared spectra analysis suggested that the degree of crosslinking reaction of Sugurome-urushi was higher than that of other urushi. The highest indentation stiffness was detected in the sample surface coated with Sugurome-urushi and Sugurome-urushi film, which have better ductile properties when compared with others. Moreover, the tangential section of Sugurome-urushi was smoother than that of the others. Increasing the hardness and smoothness of wood samples by coating with urushi could be effective in preventing termite penetration. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.