This paper summarizes the examinations on various factors governing the molecular mobility in the supercooled liquids and the glass transition temperature Tg. The examinations were performed on some thermodynamically characterized samples including a linear polymer (polyvinylchloride: PVC), a crosslinked polymer (chlorinated polyethylene: CPE), and a relatively simple molecular liquid (a mixture of triphenylchloromethane and ortho-terphenyl: TPCM/oTP). Various thermodynamic excess quantities such as the free volume and the configurational entropy and energy were evaluated as possible factors governing Tg and the relaxation time. Theoretical predictions expressed in terms of such excess quantities were compared with the experimental results on pressure dependence of Tg, and isochronal T-P relation obtained from the dielectric dispersion. The main conclusions are as follows: (1) The WLF type free volume is a good factor determining Tg and the relaxation time for TPCM/oTP, but not for the polymers; (2) The Adam-Gibbs parameter is good for the polymers, but not for TPCM/oTP; (3) The configurational entropy and internal energy are good for all of the present systems; (4) The glass transition of TPCM/oTP may be treated as a quasi-equilibrium thermodynamic second-order transition, but those of the polymers cannot; (5) The ratio of isochoric activation energy to isobaric activation energy, H*v/H*p, is 0.7~0.9 for the polymers, while H*v/H*p is less than 0.5 for TPCM/oTP. The difference in intramolecular degrees of freedom may be responsible for this difference in the value of H*v/H*p.
The mucus secreted by the uterine cervix plays essential roles in the process of human reproduction. The rheological properties of the cervical mucus vary according to the ovarian cycle. The purpose of this study is to develop measuring methods for mechanical properties of cervical mucus, which are applicable to medical test. Two new apparatuses were developed. One is to measure the velocity and attenuation of ultrasonic wave (5MHz) in a syringe employed for collecting the specimen. The other is for rapid measurement of viscoelasticity over a frequency of 1-300Hz based on the fast Fourier transform of the response (displacement) to the applied pseudo-random force, a force consisting of sinusoidally varying components with various frequencies. Examples of measurements with these apparatuses and the biomechanical spectrometer reported previously are shown for bovine cervical mucus, human cervical mucus, and human synovial fluid. Ultrasonic sound velocity and attenuation of bovine cervical mucus were 1437m/sec and 0.97dB, respectively. The bovine cervical mucus was more elastic and less viscous than human cervical mucus.
Fine acicular particles of goethite (G) was calcined to obtain equal-shaped hematite (HR). These acicular particles, G and HR, and spherical particles of pigmental hematite (H)were dispersed into ethylene glycol with and without adding alumina as the second component. Viscosity behavior of the suspensions was analyzed on the basis of energy dissipation concept, under the Bingham approximation. Of the two suspensions of similar acicular particles G and HR, the former with lower zeta-potential showed higher rate of the total energy dissipation of flow than the latter. The result was interpreted in terms of the difference of the resistance to redispersion of aggregated flow units in these dispersed systems. The apparent viscosity of the suspension of HR was much higher than that of H, despite the similar zeta-potential. It was revealed that bulkier flocs formed from acicular particles of HR were mainly responsible for its higher viscosity. The extent of heterocoagulation with alumina was also larger for acicular particles than for spherical particles. These findings show that both the effective volume fraction of the floc and the Bingham yield stress cannot be determined simply by the zeta-potential when suspensions of morphologically different particles are to be compared.
The crazing behavior of enameled wires under applying DC voltage was studied in aqueous solution of sodium chloride of various concentrations. The crazing occurred in the enameled polymer film only when test wires were connected to the negative pole. In this arrangement of the sample, weight increase of the polymer film was also observed. The craze formation was enhanced with increasing concentration of sodium chloride of the aqueous solution and also with increasing DC voltage applied to test wires. It was inferred that the penetration, due to the electroosmosis, of the hydronium ion in the polymer film is a major factor for the craze formation.
In extruding a Newtonian fluid from a duct, the pressure at each position of the duct increases with increasing flow rate. In the case of viscoelastic fluids, the pressure near the duct exit decreases with increasing flow rate when the flow rate is higher than a certain value. In this study, we determined the velocity profiles near the exit of two-dimensional ducts for a 3% aqueous solution of polyacrylamide (Separan). With the use of observed velocity profiles and the constitutive equation of Denn, we evaluated the pressure distribution in the duct. It was revealed that the transformation of the elastic energy, stored at the duct entrance, to pressure in the duct becomes less effective with increasing flow rate above a certain flow rate. This ineffectiveness of the transformation may be the origin of the abnormal behavior of pressure near the duct exit.
Change in the cross linking density of rubber vulcanizates with deformation was studied by measuring the degree of swelling of samples experienced extension. Swelling measurements were made in toluene, and the cross linking density was determined by using the Flory-Rehner equation. The decrease in the cross linking density with extension ratio occurred in three stages: rapidly decreasing stages at low and high extension ratios and a slowly decreasing stage in the middle. Stress-strain hysteresis in cyclic extension was observed. A network model was proposed to interprete the observed relation between structure and properties of the deformed rubber vulcanizates.