Tensile Relaxation Modulus Research Articles

Viscoelastic properties of UV‐curing ink systems

AbstractMechanical properties such as tensile strength, relaxation modulus, creep compliance, and storage and loss moduli of UV‐curing ink systems were examined at various drying stages. Acrylic‐based binder consisting of epoxy acrylate prepolymer and trifunctional monomer were used as UV‐curing systems. For the UV‐cured specimen containing a large quantity of trifunctional monomer a highly crosslinked network structure was formed at comparatively short irradiation time, however, the sample lacks toughness and nonlinear rheological behavior was observed. On the other hand, for the specimen containing a large amount of epoxy prepolymer, a uniform network structure was formed and the ultimate strength increased with the growing network structure. In the temperature sweep experiments for storage and loss moduli, two transitions were observed. The transition observed above 10°C shifts to higher temperature and becomes broader with increasing irradiation time. The transition which is associated with a relaxation in the crosslinks was observed at −70°C and the height of the G″ peak increased with increasing irradiation time.

Influence of gel and molecular weight on the properties of natural rubber

The influence of gel and molecular weight on the properties of natural rubber has been described. Crystallization, stress relaxation and orientation properties of different samples have been studied. Samples having different gel contents but similar molecular weights and samples having the same gel content with varying molecular weights have been prepared by extracting whole natural rubber. The gel content was varied from 1.5 to 29% and molecular weight from 1 × 10 5 to 9.9 × 10 5 g mol −1. The gels reduce the overall crystallinity measured by differential scanning calorimetric experiments after freezing the samples for different time periods at −15°C. They also have a stiffening effect on the tensile relaxation modulus and decrease the rate of relaxation significantly. Birefringence, which measures the orientation and stress-induced crystallization, increases with time at high elongation for samples containing gels. At lower elongation, however, the birefringence of unvulcanized samples decreases with time. This decrease is less for gel samples. Natural rubbers of high molecular weight behave similarly in the above properties when compared to low molecular weight samples. The effect of gel is more predominant than that of molecular weight.

Mechanical Properties Related to Soybean Seedcoat Cracking During Drying

ABSTRACT THE ultimate tensile stress and relaxation modulus of the soybean seedcoat were evaluated in two orthogonal directionsparallel and perpendicular to the hilum. An Instron Universal Testing Machine fitted with an environmental chamber was used to measure these mechanical properties for different drying conditions. Both properties were found to decrease as seedcoat moisture content and temperature increased. A three-term Maxwell model was found to adequately characterize the tensile viscoelastic behavior of the seedcoat. The seedcoat was found to be hydro-rheologically simple. Loading perpendicular to the hilum resulted in approximately 50% higher ultimate stess than loading parallel to the hilum. This anisotropic behavior may explain why over 90% of cracks in soybean seedcoat formed during drying extend from the hilum out; a situation representing loading parallel to the hilum.

かまぼこのレオロジー的物性と構造に関する研究-XIII

The tensile relaxation modulus reduced to 25°C in the time scale range from 3×10-2 sec to 1 ×106 sec was determined, and the relaxation spectrum was calculated for kamaboko. A comparison of the relaxation spectra for various kamaboko varying in tensile tough-ness (i.e., the strength of ashi) gives the following information: (1) There is a very good parallelism between the magnitude of tensile toughness and the absolute value of the dif-ferential coefficient of the relaxation spectrum at 1×10-1 sec of relaxation time. (2) There is also good parallelism between the magnitude of tensile toughness and the width of the distribution range of the relaxation times of Maxwell units which are able to relax under applied strain.

LITERATURE ABSTRACTS

LITERATURE ABSTRACTS

かまぼこのレオロジー的物性と構造に関する研究-V.

Both tensile relaxation and shear relaxation in kamaboko were examined. The results obtained were as follows: 1) By a general definition of tensile relaxation modulus, E(t)=ƒ(t)/α-1, the behavior is linear in very narrow extension ratio range, 1.0<α≤1.1. 2) By a definition derived from the equation of state for ideal rubber, E(t)=3•ƒ(t)/α-α-2, the behavior is linear in the whole measured extension ratio range, 1.0<α≤2.0. 3) The behavior in shear is linear in the whole measured strain range, and the relation between tensile relaxation modulus and shear relaxation modulus is given by the equation, E(t)=3•G(t). 4) The generalized Maxwell model or the Eyring-Tobolsky's viscoelasticity theory should be applied to the stress relaxation behavior of kamaboko.

On the calculation of tensile stress relaxation modulus for varying stress and strain

On the calculation of tensile stress relaxation modulus for varying stress and strain

Tensile Relaxation Modulus of Corn Horny Endosperm as a Function of Time, Temperature and Moisture Content

Tensile Relaxation Modulus of Corn Horny Endosperm as a Function of Time, Temperature and Moisture Content

Rheology of Gelatin Films

A procedure has been developed for the evaluation of the viscoelastic properties of gelatin films employed in soft gelatin capsule formulations. It involves the measurement of the tensile relaxation modulus of the film and the fitting of the resultant curve on an analog computer to obtain the appropriate constants. A theory was proposed for the mechanism of stress relaxation in gelatin films. Based upon this theory, an equation for the tensile relaxation modulus was derived. This equation was of the same form as the empirical equation which fit the stress relaxation curves of the gelatin films.