Studies on high-order structures of poly(ethylene terephtalate) films prepared by uniaxial and biaxial stretching processes were done using Small-Angle Light Scattering(SALS). On uniaxial stretching, a butterfly shape was obtained in the Hv light scattering pattern, which indicated the existence of a sheaflike crystalline high-order structure in the stretched films. Numerical calculations based on the sheaf array model were carried out for the interpretation of experimentally obtained SALS patterns. Results of the calculated patterns showed good agreement with experimental ones. In the case of biaxially stretched films, the SALS patterns changed remarkably depending on the stretching conditions and stretching systems. Higher stretching temperatures were found to be effective in the two-way successive stretching system since the high-order structure formed at the initial uniaxial stretching was not easily destroyed by the second stretching. Further, it became obvious that a three step stretching system in which machine direction stretching was divided into two steps was effective in obtaining biaxially stretched films having 8 leaf SALS patterns including the butterfly shape.
Enzymatically synthesized completely linear α-1,4 gulcan amylose (ESA) with various molecular weights was dissolved in water and alkaline solution. Change in the solution rheology with time after preparation was investigated. Both |η*| andG' of low molecular weight ESA in alkaline solution increased with increasing time after preparation due to the formation of crosslinking at the crystallites. Medium molecular weight ESA tended to degrade and the solution viscosity decreased with time in the alkaline solution. However the zero shear viscosity did not decrease to the value predicted from η0 = KM 3.4 relation when the concentration is high. High molecular weight ESA dissolved in water was not subjected to the degradation and show the significant increase in |η*| andG' due to the retrogradation.
The uniaxial elongational viscosity of blends, consisting of polycarbonate (PC) and a small amount of polytetrafluoroethylene (PTFE), have been studied. Uniaxial elongational viscosity of blends showed stronger strain-hardening property than that of PC. The structural observations at the fractured cross-section with SEM showed that PTFE fibrils less than 100 nm in diameter were produced by kneading in molten PC, which were dispersed uniformly in PC matrix. To get deeper insight into the mechanism of the strong strain-hardening, the recoverable strain of the blend samples was investigated, and it was found a large strain recovery occurred after uniaxial elongational deformation. The comparison of the phase morphology before and after strain recovery was performed by observing with SEM. It was confirmed that the diameter of PTFE fibrils increased after strain recovery. WAXD pattern showed that the crystallites of PTFE in PTFE fibrils orientated along the elongational direction by the uniaxial elongational deformation. DSC measurement revealed that 60% amorphous phase existed in fibrillated PTFE. It was supposed that PTFE fibrils deformed, resulting in the generation of a restoring force, during elongational deformation. These results suggested that the strain-hardening property should be attributed to the generation of the restoring force by stretching of PTFE fibrils.
In our previous study, we observed Hele-Shaw flows of two solutions of a polymer material around two cylinders and through two slits with different lengths. Based on the results, we showed that the potential flow analogy by the Hele-Shaw flow holds when the flow rate is very low in spite of the shear-thinning viscosity and elasticity of the fluids in steady shear flow. It was suggested that the potential flow pattern of the polymer solutions in the Hele-Shaw cell is disturbed by the effect of elongational stress. In this study, a simple method for planar elongational viscosity measurement is devised using the converging flow upstream the slit entry; the elongation rate is estimated from dye streak pattern in the inflow region formed upstream the slit entrance and the elongational stress is obtained from integrated equations of motion. The planar elongational rheometry presented in this work is advantageous due to its applicability to mobile fluids, in addition to its simple experimental set up.
Vortex enhancement mechanism in 4:1 planar contraction flow of a viscoelastic fluid has been investigated, where the Oldroyd-B model was considered as a constitutive equation. Finite element method was used based on the fractional step method for time marching and DEVSS/DG as a stabilizing scheme. The prediction of vortex dynamics agreed well with the experimental results. At first, a lip vortex was generated at the reentrant corner at low Weissenberg number (We). As We increases, the size of the salient corner vortex becomes reduced, while the lip vortex becomes more pronounced and finally takes over the corner vortex. The trajectory of a lip vortex at high We was found to follow the steady state positions of the lip vortex at lower We, which means that the fluid has a memory and there exists a simple relationship between We and time. Accordingly, a simple universal behavior was found to dominate the vortex enhancement mechanism in the 4:1 planar contraction flow of the Oldroyd-B fluid.
The effects of ion aggregates on zero shear viscosities η0 for ethylene-co-methacrylic ionomer melts were investigated. Rapid increasing of η0 for Zn ionomers was shown in high neutralization degree, however, the rapid increase was not observed in all range of neutralization degree for Na ionomers. These results indicate that the formation of ion aggregates strongly affects η0 only for Zn ionomers. We expect that acid cation exchange, in the case of Na ionomers, cancels effect of ion aggregates on η0. On the other hand, formation of ion aggregates affects on damping functions for both cases of Na and Zn ionomers. In the case of Zn ionomers, the value of η0 in high neutralization degree(>40%) deviated from linear regime. This neutralization degree well corresponds to the onset of strong strain dependence of h(γ). We hence consider that measurement of neutralization dependence of η0 is one of the ways to detect existence of ion aggregates in EMAA-Zn ionomer melts.
Deformation behaviors of microstructures of polyamide 6 (PA6) and elastomer-alloyed PA6 were investigated using small angle light scattering (SALS) techniques. The SALS pattern shows that PA6 has incomplete spherulitic structures. The change of SALS pattern with elongation suggests that the structures deform with external deformation up to yield strain. Then the SALS patterns discontinuously change with necking elongation and suggest that the apparent size of the spherulitic structures becomes very larger and that the degree of orientation decreases. Next lobe-streak patterns, which are considered to be due to sheaf-like structures, were observed beyond the necking elongation. These changes in SALS patterns can be explained by the reconfiguration models of adjoining spherulitic structures presented in this paper. The SALS patterns of elastomer-alloyed PA6 similarly show the existence and deformation of incomplete spherulitic structures up to yield strain. However, neither spherulitic nor sheaf-like structures were observed in the SALS patterns beyond the yield strain.
New strategy to determine the draw resonance instability using the frequency response method, first devised by Kase and Araki1) has been developed in the spinning process considering the viscoelastic nature of polymer melts. Numerical technique for efficiently evaluating the complex-valued frequency response system has been revamped in this study. By adopting the Nyquist stability criterion into frequency response, stability windows of the viscoelastic spinning system have been successfully predicted in both isothermal and nonisothermal cases. This stability-determining method as a useful analysis tool can be applied equally well to other extensional deformation processes.