Effects of styrene-co-methacrylic acid (StMAA) on melt viscosity and morphology for ethylene ionomer were studied. In this study, we used poly-(ethylene-co-methacrylic acid) of neutralization degree 54 % with sodium ions (EMAA-54Na). Dynamic viscoelasticity of EMAA-54Na/polystyrene(PS) or EMAA-54Na/StMAA blends was evaluated. EMAA-54Na/StMAA blends differed from EMAA-54Na/PS blends in rheological property. Zero shear viscosity η0 of EMAA-54Na/StMAA was higher than expected viscosity with increasing contents of StMAA. Furthermore, fall down of the damping function obtained from stress relaxation measurement of EMAA-54Na/StMAA was weaker than that of EMAA-54Na. These results indicated strong interaction between EMAA ionomer and carboxyl groups of StMAA. Results of morphological observation and Fourier transform infrared spectroscopy also indicated that the strong interaction is attractive.
The apparent viscosities of non-Newtonian fluids such as alumina, graphite slurries and carboxymethyl cellulose, starch solutions were measured by using a B-type and a vibration-type viscometers and the measured apparent viscosities were compared to those measured by a coaxial cylinder rotational viscometer, which is an absolute measurement device. It was shown that the measured values of B-type viscometer could be larger or smaller than those of the coaxial cylinder rotational viscometer when measuring various samples including dilatant fluids. It was also found that the difference between the measured viscosities by the coaxial cylinder rotational viscometer and B-type viscometer became larger as the n value determined by curve fitting of the flow curve was apart from 1.0. In addition, it was found that the measured values of the vibration-type viscometer were always extremely smaller than those of the coaxial cylinder rotational viscometer, indicating that the particles or polymers in the sample should not follow the movement of the vibrator. From the extensive measurement of apparent viscosity, we can conclude that the apparent viscosities measured not by the vibration-type viscometer but by B-type viscometer has a good connection with those measured by the coaxial cylinder rotational viscometer.
This study examines the relationship between paste properties and screen-printing phenomena. Since the printing includes multiple processes those are generated almost simultaneously, it is necessary to investigate respective processes. In this report, we have focused transfer printing processes from the screen to a substrate. We have tested model silver pastes with different surface treatment to the silver particles. Several kinds of rheological properties of test pastes were measured and results of model printing experiments and real fine line electrode printings were correlated to the properties. It was found that the shear stress characteristics in the bulk form did not directly relate to printing performance and the other factors, such as oil absorption volume which affected flowability of the paste surface, must be further important. The study also confirmed that the tendency in oil absorption volume agreed with the conventional size electrode printing performance. But, paste residual phenomena was generated in the case of ultrafine line printing with 30 μm width and printing performance was influenced with other factors because of very narrow gap generated with a mesh and open area in the screen.
For entangled polymers, there exist considerable contributions of the cross-correlation between different chains in the relaxation modulus, though the contribution is neglected in the single-chain models. Earlier studies have suggested that the cross-correlation is due to the inter-chain interactions such as the force balance around entanglements and the osmotic force suppressing the density fluctuations. However, the origin of the cross-correlation has been yet to be clarified. In this study, a new multi-chain slip-link model has been developed for the simulations of polymer dynamics without the inter-chain forces while the creation of entanglement is performed according to the geometrical manner and the local equilibration. The simulations reproduced the qualitative features of entangled polymer dynamics for the molecular weight dependence of the longest relaxation time and the diffusion coefficient, just as expected from the success of the earlier single-chain models without the inter-chain forces. On the other hand, the remarkable feature of the model is that the cross-correlation exists between chains, suggesting that the cross-correlation is generated via the local equilibration at the creation of entanglement even without the global equilibration by the inter-chain forces.
Dynamic surface tensions of aqueous solutions of polymers were measured using a measuring device based on the maximum bubble pressure method. The measurements implied that extra increase in the measured surface tension was induced by the elasticity of the polymer solutions at high frequencies of bubble life cycle. Furthermore, at high polymer concentrations, the surface tension exceeded that of the solvent. These results mean that the measurements for polymer solutions having strong elasticity with the maximum bubble pressure method correspond to apparent dynamic surface tension including the effect of elasticity.
It is well known that the elongational viscosity ηE of the Hookean dumbbell model increases with increasing elongational strain rate ε and finally diverges to infinite on approach of ε to 1/2τeqH, where τeq His the viscoelastic relaxation time of the Hookean dumbbell that does not change with ε. This divergence of ηE reflects infinite extensibility of the Hookean dumbbell. Real polymer chains obviously have the maximum stretch limit, so that the dumbbell model with a finite extensibility was developed almost a half century ago as a model for those chains under strong flow. This model exhibits the finite extensible nonlinear elasticity (FENE) effect under strong flow to provide ηE with the strain-hardening feature but without any divergence. This FENE dumbbell model has been mathematically analyzed in detail and is now well established. Nevertheless, in a naive expectation, stiffening of the FENE dumbbell could/should largely increase the viscosity. Thus, it is still desired to explain, on an intuitive physical basis, how the stiffening suppresses the divergence of ηE. From this point of view, this study focuses on the effective relaxation time τFeff of the FENE dumbbell under steady elongational flow. It turned out that the stiffening of the FENE dumbbell leads to a decrease of τFeff in proportion to ε−1 at ε > 1/2τeqH, and this decrease of τeff allows the effective Weissenberg number of the FENE dumbbell under flow, WiFeff = ετFeff, to stay below a critical value of ~1/2 even for ε→∞. This limited increase of WiFeff allows the FENE dumbbell to change its conformation just slightly even for a large increase of ε from 1/2τeqH to any higher value, which naturally leads to the lack of divergence of ηE.