Polypropylene crystallizes in the monoclinic form in slow cooling, and in the pseudo-hexagonal (smectic) in rapid cooling. In melt spinning of polypropylene, we found out that the undrawn filament with high birefringence is obtained by rapid cooling before the crystallization begins in the filament (i. e. before the remarkable increase in the birefringence takes place.)
This rapid-cooled filament is consisted of the highly oriented small paracrystals (smectic modification).
When the rapid cooling was made, even in low take-up speed, the elongation decreases and the apparent strength becomes higher as compared with the filament made by the conventional spinning.
The cold-drawing of the rapid-cooled filament at low draw ratio is accompanied by further increase in the apparent strength and the decrease in the breaking elongation.
These rapid cooling effect of spun filament is influenced by the spinning stress and filament temperature just before the cooling, however, the melt temperature is the important in our experiment. At low melt temperature, we could not observe remarkable rapid cooling effect in spite of the occurrence of the smectic structure, and thus the melt temperature is considered to play an important role for the cooling effect.
From the result of the molecular degradation by increase of melt temperature, it is considered that the decrease in the molecular weight should be concerned with the movability of molecules, which should contribute to the high orientation of paracrystals.

View full abstract

Thermal properties of sericin have been studied by means of DSC method. The results obtained are summarized as follows:
1. Soluble sericin with a low crystallinity gave a DSC curve where an endothermic main peak and a shoulder were observed at ca. 220°C to 230°C and ca. 250°C, respectively. The soluble sericin became highly crystalline by swelling in water and gradually drying. The crystalline sericin obtained showed a main peak at ca. 250°C and a shoulder at ca. 220 to 230°C on the DSC curve, subsequently the solubility of the specimen decreased remarkably, i. e. hardly soluble or insoluble sericin.
2. It has been found from the DSC analysis that quickly dried sericin was a soluble type and gradually dried one was a insoluble type.
3. The insoluble part of sericin in water found to be an insoluble type of sericin in cocoon filament.

View full abstract

The effect of stirring on the polymerization of ethylene induced by γ-irradiation in a gaseous phase was studied with regard to the morphological features and the physical properties of resultant polymer. The melting temperature, the heat of fusion, the density and the content of CH₃ groups of the polymers formed were independent of the stirring speed, but the specific surface area of the material showed a minimum in the range of 200-500 rpm. Similarly, the viscosity-average molecular weight showed a minimum at a speed of ca. 200 rpm. GPC molecular weight distributions showed double peaks which is characteristic of low-temperature polymerization product. The higher molecular weight species increased with increased stirring speed. The fibrillar morphologies observed under a scanning type electron microscope increased drastically with increased stirring speed. Close inspection of these fibrils revealed that many nodese fibers were produced by a partial unfolding of molecules in the lamellar crystals. It is likely that the increase of fiber-like structures leads to the increase in the specific surface area of the resultant polymers, so that the number of contact of long-lived radicals in the resultant polymeric solid with monomers increases, giving rise to the chain growth and the grafting, which produces long chain branches, and consequently the polymerization rate is accelerated.

View full abstract

In order to study the dyeing property of Spandex, diffusion of p-nitroaniline (PNA) and p-aminoazobenzene (PAAB) and stress relazation of the samples (F-70 and T-280) were studied both at T=40-90°C in the dry state and following results were obtained.
(1) Diffusion coefficient D vs. 1/T is expressed by two lines intersecting at T_d=64-66°C, Apparent activation energy of diffusion (ΔE_d) is estimated to be about 18-20kcal/mol and 40kcal/mol for T>T_d and T<T_d, respectively. ΔE_d is slightly larger for PAAB than for PNA.
(2) Reduced relaxation modulus vs. log t superposable to yield a master curve. Logarithm of shift factor a_T vs. l/T is also linear and having a break at T_r, which is in good accordance with T_d. Activation energy of relaxation (ΔE_r) is close to the value of corresponding ΔE_d.
(3) Log D vs. log a_T is linear and breaks at the corresponding temperature with T_d or T_r. The slope of the line fluctuates slightly in the vicinity of unity as required by the theory.
(4) Both D vs. T and a_T vs. T obey to the WLF formula, where the observed parameters c_??_ and c_??_ are close to the theoretical values for T>T_d(T_r) but larger for T<T_d(T_r).
(5) The above mentioned behaviors of F-70 are very similar to those of T-280, although the former is of ester type while the latter is of ether type.
It is concluded that the soft segment behaves as similarly as amorphous polymers above T_g especially at temperature higher than T_d or T_r.

View full abstract

In the previous study it was pointed out that poly (ethylene terephthalate) (PET) fiber treated with high concentrated sulfuric acid had good dyeing properties not only for a cationic dye but also for disperse dye.
This study was attempted to clarify the relation between treating conditions of PET fibers with sulfuric acid and tensile strength or amount of disperse dyes adsorbed in the fibers.
Sulfation of PET fibers was carried out with wider treating conditions than that of on the previous study, i. e. the sulfation was carried out with sulfuric acid of 70_??_77% at 90_??_100°C for 1_??_180 min. The reason for the high affinity of sulfated PET fibers to disperse dyes was also discussed.
The fiber prepared with suitable condition has good dyeing properties and good fastness against light and washing. The tensile strength of fiber thus prepared is just as high as that of untreated fibers.

View full abstract

In this study the tensile testing was made as a function of direction for the triaxial fabrics with 48 yams made by a braiding machine. In the testing, the specimens with different directions from the machine direction were taken out and provided the measurements of the load-elongation curves in the light load.
The results were compared with those of the arthogonal fabrics.
The following conclusions are obtained:
1) The cover factor of triaxial fabrics is shown as;
then α=60 and C=67%.
2) The ratio (n) of the specimen length to chack width and the angle θ between the axis and yarn are varied, the number of kinds of yarns holding both ends is varied between 0_??_3, as shown in Fig. 5.
3) When experiments are made at n=1, triaxial fabrics have less directional properties with regard to the load-elongation than orthogonal fabrics.

View full abstract