A semiempirical equation on the life time, t_b of polymeric materials under tensile creep has been proposed. The present equation can be reduced to the Holland-Turner equation for low stress region (σ≤σ_C) and to the Zhurkov-Narsulaev equation for high stress region (σ_C<σ<σ_Y), where σ, σ_C and σ_Y are the applied stress, the characteristic stress, and the yield stress, respectively. As for the stress dependence of the life time, a good agreement was found between predicted behavior of this work and reported experimental results. The characteristic stress is affected by the factor such as the activation volume, the internal stress, σ_i and σ_Y. The decrease of σ_C with increasing temperature arises from the decrease of σ_i and σ_Y with temperature. It has been also shown that the temperature shift factor for reducing the plots of ln t_b vs. ln σ to a master curve can be written as a function of the activation energy of σ_i and σ_Y.

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Anisotropic relaxation functions for some machine made papers were determined experimentally on the basis of the theory of linear viscoelasticity.
For a material which has the orthotropic anisotropy and is subject to in-plane stresses, there are five independent in-plane relaxation functions, of which two (G₁₂, G₂₁) must be equal if the relaxation functions are symmetric (G_ijkl=G_klij). These relaxation functions can be determined from the measurements of stress relaxation under the strip biaxial tensile condition in the three directions: the machine direction, the cross machine direction and the direction at 45 degrees to the machine direction.
Measurements were made using a biaxial tensile tester for regular kraft paper samples, untreated filter paper samples, and the filter paper samples which had been immersed in water and then dried without restraints in order to release the so called dried-in stress.⁵⁾ The estimated relaxation functions G₁₁(t), G₂₂(t) and G₃₃(t) for filter paper samples (treated and untreated) showed similar time dependence which was expressed as G_ii(t)=G_iig(t), whereas those for kraft paper samples showed large differences among them. The differences between G₁₂(t) and G₂₁(t) were of the order of experimental errors. Anisotropic relaxation functions for these paper samples at t=1(sec) were represented schematically and compared with each other.

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The chemorheological properties of purified uncrosslinked polybutadiene rubber were examined under various conditions. Intermittent stress relaxation measurements were performed for specimen of various thermal histories in unstretched conditions; i. e., various combinations of temperature and exposure time interval ranging from 30°C to 245°C and from 0 min to 150 min, respectively. The time scale of the measurements, ranging from 0.01 sec to 10 sec, was so short compared with that of unstretched states that one can neglect the chemical reaction under stretched states. This method was found good for measuring the effects of chemical and physical relaxation separately. The effect of chemical reactions can be examined by using the relaxation modulus as a function of exposure time.
In spite that the specimens were held in the nitrogen gas atmosphere, remarkable gelation took place at higher temperatures. Dependence of isochronous values of relaxation moduli on the exposure time suggested the existence of two types of gelation reaction. One was a rapid reaction observed at short exposure time and the other was a slow one at relatively long exposure time. From the Arrhenius plots, two types of activation energy of gelation were observed. The activation energy, ranging from 24 to 36 and from 0 to 5 kcal/mol, showed the marked time dependence. It may correspond to the difference in molecular weight and molecular weight distribution of the sample. The measurements were also performed on the infrared spectroscopy and swelling.

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The kinematic viscosity measurements of the ASTM (American Society for Testing and Materials) standard oil samples have been carried out as the ASTM cooperative kinematic viscosity testing program under the supervision of the ASTM since 1959. Our laboratory has taken part in this testing program every year since 1969.
This paper describes the results of kinematic viscosity measurements obtained on the standard oil samples with normal flow U-tube master viscometers at our Laboratory and the results of comparison among the data obtained with each capillary-type master viscometer at foreign national laboratories and our laboratory over the period from 1969 to 1978.
It is concluded that the difference between the viscosity measurements obtained at our laboratory and the foreign national laboratories is within±0.2% in the range of viscosity less than 2.4×10³mm2/s(cSt) and +0.00-+0.42% in the range less than 8.1 × 10⁴mm2/s(cSt) over the temperature range from 20 to 40°C.

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Measurements of the diameter, temperature, and birefringence of fibrous materials running from spinneret toward a winding machine during the melt spinning of polyethylene terephthalate (PET) were carried out. A specially designed spinning machine which enables us to measure the above variables was constructed. The measurements were carried out without touching the running fiber by employing various optical devices. Particularly, an infrared radiation microscope was employed successfully for the temperature measurement.
Changes in observed diameter, temperature, and birefringence and in calculated values of velocity and rate of deformation of the running fiber along the spinning line were similar to those reported by other authors. The thinning in the diameter of the running fiber seemed to be completed within a distance of two meters down from the spinneret. An estimation of the magnitude of the two components of dynamic loss compliance J″ of PET, J_i″based on the recoverable viscoelastic deformation and J_η″based on flow, was made for temperatures at different positions along the spinning line. The changes in the diameter and birefringence of the running fiber were explained qualitatively with the relative magnitude of J_i″and J_η″. In the zone below and close to the spinneret where J_η″>>J_i″, flow is dominant resulting in the rapid thinning in the diameter of the running fiber. On the contrary, in the zone where J_η″<<J_i″, recoverable deformation is dominant resulting in the very little change in the diameter of the running fiber. A comparison of the relative contribution of J_i″and J_η″and the magnitude of the birefringence leads us to an idea that the inter- and intra-molecular forces which are responsible to the recoverable deformation, may work effectively in molecular orientation. The rate of relaxation of molecular orientation was evaluated by calculating relaxation times according to a Maxwell model. The increase in relaxation time may be a part of the reason for the increase of the birefringence in the zone where cooling proceeds effectively.
An analysis of the change in the diameter and temperature along the spinning line was carried out numerically using equations of force and heat balances. Because the material parameter used in the force balance equation is only extensional viscosity, the agreement between observed and calculated values was limited in the high temperature initial zone of spinning where flow is dominant in the deformation of running fibrous materials.

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An equation for the powder discharge from a vertical tube is derived theoretically by combining the Janssen equation of the pressure distribution with a dynamic balance equation of forces for falling non-cohesive powders. The derived equation is similar in form to Shirai's equation which is based on an empirical pressure equation and an orifice equation. In cohesive powder systems, we assume that a cylindrical block with a certain height is formed at the bottom of the tube and it moves out from the tube. The block height is calculated from a dynamic force balance. A periodic discharge of powders is predicted. This is similar to the results by Tanaka et al. who analysed the motion of powder by using different values for static and dynamic Rankin's coefficients.

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The constitutive equation of Schapery, which describes the stress in terms of strain history under uniaxial deformation, is transformed into an equation for expressing the strain with the aid of the method of undetermined coefficients and multipliers. For simplicity, it is assumed that the relaxation modulus is proportional to some powers of time and strain (Nutting model). The functional form of strain equation as well as the coefficients and multipliers are assigned so as to express stress relaxation and creep rigorously. The derived equation has a modified form of another equation of Schapery, which describes the strain in terms of stress history under uniaxial deformation. The obtained equation can be used to predict the strain under the continuous and monotonous stress history, for example loading at constant stress- or strain-rate. However, if the stress history or its derivative has discontinuity, such as in two step stress-relaxation (creep) and stress relaxation after stop of slow loading, the equation fails to express the strain at a given time.

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