The structural changes and development of morphology, crystal structure and mechanical property upon uniaxial drawing of an equimolar blend of high-molecular weight poly(L-lactic acid)/poly(D-lactic acid) (PLLA/PDLA) were investigated. Solvent-cast film of the blend were drawn by a tensile force and solid-state coextrusion. The initial film was consisted predominantly of α-form crystals and a small amount of stereocomplex (SC) crystals. Although the amount of SC did not increase upon annealing the solvent-cast film at 200°C, it increased (with draw ratio) upon drawing by either of the draw techniques when the draw was performed in the temperature range between the melting temperature of α-form crystals (T_m^α = 170-180°C) and SC (T_m^SC = 220 °C). Upon drawing at a given temperature, SC formed significantly more rapidly with draw ratio for the solid-state coextrusion than for the tensile drawing. Thus, an oriented product consisting of only SC was obtained by the solid-state coextrusion at T_e = 200 °C to an extrusion draw ratio of 16, even for a high-molecular weight PLLA/PDLA blend, although the formation of SC in such a blend has been shown to be difficult in bulk from melt or in solution. The dynamic Young's moduli of SC samples above T_g (∼60 °C) was significantly higher than that of an α-form sample.

View full abstract

As the basic study to investigate the mechanism of improvement in the dyeing fastness of natural dyes on silk fabrics, the optical behavior of tannin solution, the optimal condition of tannin treatment and the changes of the physical structure of silk fabrics were studied in the treatment of tannin. As the tannin content of silk fabric was increased, the value of ξ-potential became negative. As the tannin content of silk fabric was increased, the crystallinity and crystallite size were decreased. The degree of orientation was also decreased with the tannin treatment. As the concentration of tannin was increased in its treating condition, the tannin content and K/S value of tannin-treated silk fabrics were increased. Because tannin gave rise to yellowing by hydrolysis and oxidation at high temperature, the higher tannin-treating temperature resulted in the lower the tannin content and K/S values of silk fabrics. The tannin content of silk fabric was higher in acidic treating condition and the highest K/S value was showed at pH 5. The optimum condition of tannin pre-treatment was 0.15% concentration, pH 4, 70°C, and 45min, and that of post-treatment was 0.05% concentration, 60°C, and 30min. The wash fastness and the light fastness were enhanced to 4 grades and 2~3 grades, respectively.

View full abstract

In order to construct an intelligent functional nano-interface, the self-organized structure of Langmuir-Blodgett (LB) films was studied using a well-defined triblock copolypeptide amphiphile as a film component. A surface structure of the LB film expressed a stripe nano-pattern unit assembly based on a phase separation. This note describes the effect of surface pressure and pH of the subphase water on the monolayer formation of the copolypeptide at the air-water interface.

View full abstract

We studied the dyeing of meta-type aramid fabrics with pigment-state vat dyes and disperse dyes using semiconductor laser. After printing the paste which involved infrared rays absorber, semiconductor laser was irradiated for a short time. As a result, it was found that each dye penetrated into the inside of the fiber, and that dyeing was possible with the comparative good result of dyeability and fastness. And then, we made continuous laser thermosol dyeing equipment using semiconductor laser experimentally.

View full abstract