สำนักราชบัณฑิตยสภา

«“√ “√ √“™∫— ≥±‘ µ¬ ∂“π Usa Sangwatanaroj, et al. 141 ªï ∑’Ë ÛÚ ©∫— ∫∑’Ë Ò ¡.§.-¡’ .§. Úıı surface and improving the filament cleanliness and whiteness. Not only could the machine reeling improve silk whiteness, degumming also could increase whiteness. All the degummed filaments gave a higher whiteness value than that of the raw filaments in which the degummed Chinese silk had the highest whiteness of 85, followed by the degummed local silks of Chul 6 and Chul 1 (72-78). The degummed yellow silk Chul 4 had less negative val- ues in whiteness than its raw silk. This result indicated that the degumming process could have removed sericin and color sub- stances coated on the filament surface, leaving silks cleaner and whiter. Denier Generally the fineness or de- nier of each silk filament is 1.25 deniers and the double filament gluing together with sericin is in the range of 1.75-4 denier. In this study, it was shown that double filament of the Chinese silk had 2.2 denier for the raw silk and 2.1 denier for the degummed silk while that of the local silks had various degrees of finenesses from 2.2 to 2.5 denier for both the raw and the degummed silks. The only one local white silk reeled by machine, Chul 1, had about the same fine- ness as the Chinese white silk also reeled by machine. Other local silks were coarser than the Chinese silk. The degummed silks showed the same denier as their raw silks. Differences in fineness among various silk varieties could be due to their different parental genetics, and raising diets and climates, and many other environmental con- trols. Silk varieties of mixed hy- brids among the Thai race and the Japanese or the Chinese race called Chul 4 and Chul 6, respectively, had slightly larger deniers (2.3-2.4 denier) than the silk variety of the mixed hybrid among the Japanese and Chinese races called Chul 1, and the Chinese silk (2.1-2.2 de- nier) when comparing between the machine reeled silks. In addition, it was found that the machine reeled filaments (2.2- 2.4 denier) had slightly smaller deniers than the hand reeled filaments (2.4-2.5 denier) when compared within the same silk variety and this could be because the high speed of machine reeling controlled the filament drawing ratio and hence reduced the filament size or denier. Degumming Loss To remove silk sericin and to improve water and dye absorption of the filaments, degumming is an essential step in silk production. The silk weight loss after the degumming was due to the loss of silk sericin. Generally, silk loses approximately 20% of its weight during degumming. In this re- search, the silk filaments lost 18.4 -22.4% of their weight after the degumming. The Chinese silk lost the least weight of 18.4%while the local silks lost 19-22.4%. The local silk variety of mixed hybrid between the Japanese and Chinese races Chul 1 lost the highest weight. Differences in the filament weight loss or sericin loss among various silk varieties could be due to the different sericin contents in each filament (different paren- tal genetics, raising diets and climates). In terms of silk reeling methods, it was shown that the machine and hand reeled filaments exhibited approximately the same weight loss or sericin loss upon degumming. The amount of sericin on each silk variety was less affected by the reeling methods but more affected by genetics, raising diets and climate. Moisture Content Generally, silk has about 9% of moisture content at 21 º C and 65% RH (relative humidity). In this study, moisture content of the degummed silk filaments was found between 7.9-8.8% while that of the raw silk filaments was 7.4-10.2%. The raw silk filaments are mainly composed of fibroin, covered with sericin substances (amorphous structure) which are capable of moisture absorption. Silk fibroin also contains portions of amorphous and crystalline re- gions to absorb water and streng- then the filament, respectively. Various silk filaments contain different amounts of sericin and different portions of amorphous and crystalline regions. Among the silk varieties used in this work, it was found that the