加圧時における高分子の超音波解重合 : 加圧時のキャビテーション作用の研究(第1部)

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In this report, we took notice of the degradation effect of the 28kHz ultrasonic cavitation produced in polymer solutions such as the polystyrene-benzene or polyvinyl pyrrolidonwater solution, and examined the effects of the static pressure and the excitation mode of a transducer to the polymer degradation. Ferrite transducers (28kHz) are attached to the 1/2 wavelength-resonant step horn of stainless steel, and they are excited by an RC-oscillator or a function generator and a broad band power amplifier. The sample volume of the liquid tested is about 18cm^3 and the temperature change during the experiment was held at ±1℃ by a cooling system that was set outside the pressure vessel. Using the polystyrene-benzene solutions (whose mean molecular weights are No. I=3. 23×10^5, No. II=1. 81×10^5, No. III=1. 76×10^5), we examined first the change of intrinsic viscosity with the ultrasonic irradiation time (Figs. 2 and 3), and obtained the results that the intrinsic viscosity decreases rapidly within 30 minutes of the irradition time and the rate of decreasing of viscosity has its maximum at a static pressure value of 9kg/cm^2, which is small under a high temperature in spite of the high intensity of ultrasound. Next, under the condition of constant irradiation time we examined the change of intrinsic viscosity with the static pressure value, and obtained the results that the polymer degradation effect of cavitation has its maximum under a static pressure value of several atmospheres and it is weakened above that pressure value, but is recognized up to the elevated pressure value of about 20kg/cm^2 in spite of using a relatively weak intensity of ultrasound (Figs. 4 and 5). As shown in Fig. 4, the rate of decrease of the intrinsic viscosity increases with the irradiation time and that a tendency to the static pressure value is nearly the same regardless of the irradiation time. As shown in Fig. 5, in case of the same temperature of experiment, the pressure value at which the polymer degradation effect of cavitation has its maximum increases with the intensity of the ultrasound. Under the conditions of the same intensity and temperature, we cannot obtain a sufficient viscosity decrease as the concentration of polymer solution becomes greater. Using the polyvinyl pyrrolidon-water solution (whose mean molecular weight is about 7. 0×10^5), we examined first the change of intrinsic viscosity with the ultrasonic irradiation time as a parameter of the ultrasonic intensity (Fig. 6), and obtained the results that the intrinsic viscosity monotonously decreases with the irradiation time and the rate of decrease of the intrinsic vicosity is very large in spite of a relatively weak intensity of ultrasound. Next, using a continuous irradiation and a burst pulse irradiation of ultrasound, we tried to examine the polymer degradation effect of cavitation. Under the atmospheric pressure we compared the degradation effect between the continuous irradiation and the burst pulse irradiation (burst time is 10msec and rest time is 20msec) in case of the same net irradiation time (Fig. 7). The results indicate that, in case of burst pulse irradiation, the intrinsic viscosity generally decreases more rapidly than in case of continuous irradiation, and the inclination is shown clearly under the condition of a short irradiation time. When the net irradiation time is 15 minutes and constant, we examined the change of intrinsic viscosity of the PVP-water solution in the temperature range of 20℃, 30℃ (Figs. 8〜10) and obtained the same results as mentioned above.
社団法人日本音響学会の論文
1976-05-01

加圧時における高分子の超音波解重合 : 加圧時のキャビテーション作用の研究(第1部)

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