A traditional textile technique, braiding, attracts a great deal of attention in the field of fiber-reinforced composites. To supply near-net-shape preforms for various designed composites, the flexibility of carriers' action in braiding machines must be improved. Since the publication of our previous study, we have improved our self-propelling carrier system. In this study, the carrier comprises a line-tracing robot, a wireless communication module controlled by a microcomputer, and batteries. Four prototype carriers are controlled for synchronization by the network coordinator via wireless communication. The improved system works well when testing its consecutive braiding action. Using the proposed system, we produced cord braids (using actual yarn) of adequate length in most trials. We therefore conclude that the concept of a self-propelling carrier is well demonstrated.
In order to introduce bulkiness in raw silk, this study was taken up. Calcium nitrate chemical was used to impart bulkiness in the bivoltine raw silk produced from CSR 2 x CSR 4 race cocoons reared in India. Using the Box-behnken method experimental design in which 27 different combinations are formed to standardize the process variables viz., twist levels, chemical treatment temperatures, durations and chemical concentrations. The bulky raw silk thus produced was characterized for change in diameter, add-on %, tenacity, elongation, shrinkage %, Bulk shrinkage, crimp concentration, skein shrinkage and crimp recovery using standard testing procedures. It was observed that bivoltine raw silk twisted to the level of 1500 TPM and treated with calcium nitrate solution having 5.5% concentration at 75°C for 45 seconds duration has imparted required bulkiness in the yarn and having characteristics suitable for production of chemically treated bulky silk fabric.
A reflection-model-based method for digital archiving of silk textiles is proposed. Archive data is rendered as three-dimensional (3D) computer graphics (CG) images. In this study, we describe a reflection process on a silk textile using a mathematical model (i.e., the reflection model). The reflection properties of the silk textile are quantified as the reflection model parameters obtained from measured data. To determine the reflection model parameters, we developed two systems for measuring the reflection properties and surface structure of a silk textile. The first system uses a goniometric multiband camera system to measure the spectral reflectance and surface reflection properties of a silk textile. We then estimate various reflection model parameters using the device for measuring the reflection intensity. The second system measures the 3D surface structure of the silk cloth. To estimate complex reflections, such as those from glossy silk, we developed a system to measure the microscopic 3D form of the object's surface. We also developed an estimation method with statistical analysis of multispectral information obtained by a multiband camera to estimate spectral reflectance. We use a photometric stereo-based method to estimate the microscopic 3D structure of a silk cloth. The reflection model parameters employed as the reflection properties are estimated from camera measurements of reflection intensity and the microscopic 3D structure of the target surface obtained at different illumination and viewing angles. We then render a realistic 3D CG image of the silk textile using the reflection model and the estimated data. We confirm the validity of the proposed method visually. The accuracy of the spectral reflectance estimation results is confirmed by comparing the proposed and previous methods. The proposed method with a multiband camera showed higher accuracy compared with previous studies.
An unnatural amino acid, 4-chlorophenylalanine (ClPhe), was incorporated into silk fibroin of Bombyx mori silk fiber in place of a portion of the phenylalanine (Phe) residues using transgenic silkworms that can incorporate unnatural amino acids (4-substituted analogues of Phe) into protein biosynthesis in the posterior silk glands. Raw silk fiber containing ClPhe in silk fibroin was reeled from cocoons, and its characteristics, such as its tensile properties, were investigated. The thermal properties of the degummed fiber were also characterized. The results indicated that the partial replacement of Phe to ClPhe in silk fibroin did not affect the basic properties of Bombyx mori silk fiber.
We bred a new race of silkworm, ‘J701×C701’, to improve double cocoon productivity. About 40% of larvae produced double cocoons when a V-shaped cocooning frame was used. Nevertheless, harvesting cocoons from this frame is laborious because the cocoons must be handled manually. Consequently, a rotary cocooning frame for double cocoons that is adaptable to an automatic cocoon harvesting machine has been earnestly sought. Harvesting cocoons from a rotary cocooning frame is simple and quick when using an automatic harvesting cocoon machine. We constructed cells (6 cm wide, 4.5 cm long, and 3 cm deep) to produce the rotary cocooning frame. Results show that about 60% of larvae produced double cocoons when the rotary cocooning frame was used. Double cocoon production using this rotary cocooning frame was more efficient than that using the V-shaped frame. Moreover, cocoons produced with this frame were of high quality.
Tsumugi yarns are hand-spun silk yarns produced from floss silk. In a previous study, we have introduced the truncated Polya–Eggenberger distribution to describe the variation in tsumugi yarn width. In the present study, we have applied this technique to tsumugi yarns with varying thicknesses. The results show that the width distributions in tsumugi yarns are well described by the model, independent of their thickness. Furthermore, estimated parameters related to scale factor show a proportional relationship. Thus, the width distribution in tsumugi yarn can be described by only two factors—scale and shape.
Since the silkworm tends to be disease, rearing room must to be kept clean. Therefore, it is important that disinfection of rearing room by formaldehyde gas fumigation regularly. However, formaldehyde is extremely harmful to the human because it has an allergic and carcinogenic. So far, a high-concentrate formaldehyde gas must be ventilated from the rearing room to atmosphere after formaldehyde gas fumigation. We report a new formaldehyde gas fumigation method featured by using the decomposition apparatus of a formaldehyde gas.
Silk fibroin is difficult to keep in aqueous solution for long periods because flocculation or gelation of silk fibroin is readily induced by factors such as concentration, temperature, and pH. In this research, we developed an aqueous solution of silk fibroin that is stable for long periods by using a combination of components that are already used as cosmetic materials. We combined a compound containing a guanidino group (urea, aminoguanidine, or L-arginine) with a cyclodextrin, and added them to an aqueous solution of silk fibroin (2%) adjusted to the pH 5 with dilute hydrochloric acid. The resulting silk fibroin mixed solution was placed in a constant temperature bath at 40°C and the stability was evaluated as time passed. We found that an aqueous solution of silk fibroin that was stable for more than 90 days could be prepared by addition to aminoguanidine or L-arginine and hydroxypropyl-β-cyclodextrin. Furthermore, the results of skin absorption tests of silk fibroin mixed solution with 7-methoxycoumarin indicated that the skin permeation increases in proportion to the concentration of silk fibroin.
Silk aerogel has been prepared from liquid silk, and the influences of the gamma rays-irradiation on the mechanical properties have been investigated. It seems that the formation of crosslinking in the sericin fractions induced by the gamma rays-irradiation has brought about the hardening of the aerogel.
Silk fibroin, which is recognized as a biocompatible material for use in medical applications, has a long history of use as a surgical suture extending to the present day. We have developed a novel fabrication process for fibroin sponges. To use fibroin sponges in medical applications, safety evaluations in a living body must be done. We performed sensitization, skin irritant, intradermal, genotoxicity, and human skin patch tests according to standard guidelines (Basic Principles of Biological Safety Evaluation Required for Application for Approval to Manufacture Medical Devices). All tests conducted in this study yielded “negative” results: the fibroin sponge is a safe material for medical applications.
Possible dependence of calcium and potassium contents in silk of Bombyx mori on the rearing seasons has been investigated, and it has been found that those contents in the middle division of the middle silk gland could be affected by the rearing seasons. However, those contents in raw silk fibers were almost unchanged although the calcium content in mulberry leaves for the diet of silkworms increased with advancing the season.