OKANO Toshihiko Gunma - ken Cocoon - Inspection Center, Researcher, 研究員
HAMANO Kunikatsu Tokyo Noko University, Department of Agriculture, Assistant Professor, 農学部, 助教授 (60015089)
IWANARI Yoshitaka Tokyo Noko University, Department of Agriculture, Honorary Professor, 農学部, 名誉教授 (40014899)
|Budget Amount *help
¥5,200,000 (Direct Cost: ¥5,200,000)
Fiscal Year 1991: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1990: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1989: ¥3,100,000 (Direct Cost: ¥3,100,000)
The size of cocoon filament is approximately 2.5 deniers in many of the current silkworm races. The present study was undertaken in order to obtain thick cocoon filaments and, using them, to produce silk textile of characteristic feeling.
It was found that the suitable condition for obtaining jumbo cocoons was cutaneous application of 20-100 mug juvenile hormone per larva to the, one-day-old 4th-enstar larvae reared on artificial diets. Thus, the span of the 4th instar was elongated, the weight of the newly-ecdysed 5th-instar larvae increased, and finally jumbo cocoons were obtained. For instance, the size of cocoon filament of jumbo cocoon obtained after the application of juvenile hormone ranged from 4.6 to 4.7 deniers in a specific silkworm race which produced usually thick cocoon filament(ca. 3.8 deniers).
Subsequently, many silk threads of 27 deniers were reeled using various types of cocoons of different races, respectively, and their physical properties were examined. As a result, the rate of elongation of silk thread became large, the strength of silk per unit size of filament became small, and its Youngs modulus became small, when thick cocoon filaments were used as materials for silk threads. In other words, when large size of cocoon filament was used, the silk thread of high flexibility was produced, and an advantage was also recognized in the physical properties as a thick silk thread.
Furthermore, using a number of jumbo cocoons, raw silks of 27 deniers were reeled. Exactly a hundred threads of the raw silks were yarned in doubling, twisted into a S-twist, and degummed. Then a knitting(Tenjiku)was made using the silk threads thus obtained. This knitting was superior to the usual goods in several respects, and according to the opinions of the fabric maker and the specialist of quality estimation the nature of those silk threads could be appreciated as textile materials for new goods.