Polyamide chain was introduced in the Zn ion ionomer made from ethylene-methacrylic acid copolymer and its effect on the heat resistant adhesive properties was investigated. The heat resistant temperature of the ionomer was enormously improved by compounding 5-20wt% of polyamide oligomer with primary amino end group into the ionomer. The resulting composite was thermoplastic and exhibited unusual thermo-adhesion behavior. Although the composite was capable of thermo-adhesion at the temperature as low as that for the component ionomer, it did not creep significantly up to the temperature considerably higher than the adhesion temperature. To clarify the cause and mechanisms of this unusual function, rheological measurements were made on the composite. The following features were revealed. The composite exhibited highly non-Newtonian flow behavior in the temperature range between the melting point of the component ionomer (85-105°C) and that of polyamide oligomer (180-215°C). The viscosity of the composite was much higher than that of the ionomer at low shear rates, leading to the improved heat resistant adhesive properties. With increasing shear rates, the viscosity of the composite decreased down to that of the ionomer, leading to the ease of thermo-processing and adhesion of the composite. In the composite, ammine complex salt was formed between Zn ionomer and polyamide oligomer through coordination of amino end group of the latter to zinc carboxylate of the former. In the above-mentioned temperature range, microphase-separated structures were formed in the composite. The solid phase microdomains of polyamide chains were dispersed in molten matrix of ionomer, and these phases were connected by coordination ionic bond. The thermoplastic and non-Newtonian behavior of the composite resulted from the destruction of the microdomains under high shear rates and the decrease of the ionic bond strength under high shear rates and high temperature.
The shear stress-shear rate behavior of a thixotropic coal-water mixture(CWM) was studied in a coaxial rotating cylinder rheometer under a wide variety of rest and shear rate history. The transient stress data were used to construct equilibrium and constant-structure flow curves. These transient stress data, i. e. the stress relaxation data and the stress recovery data, were also used to evaluate the breakdown and buildup processes of the internal structure. A phenomenological thixotropy model, which had the structural stress as a thixotropic structural parameter, was proposed. Dependence of thixotropic parameters on pH values of CWM was experimentally determined. Strong dependence of the time constant for buildup of structural stress on pH values was observed, and this phenomenon corresponded to the rapid coagulation of coal particles at lower pH values. However, coagulation and dispersion of coal particles could not be explained by the simple hetero-coagulation theory with measured zeta-potential values.
Mechanical properties of natural rubber vulcanized in dry and swollen states were investigated to elucidate the difference in network structures. The value of Mooney-Rivlin's C2 term for the solution-cured (SC) sample was almost zero, and was dependent on volume fraction of rubber during crosslinking. These facts suggest that the C2 term is closely related to entanglements. On the other hand, for the dry state-cured (DC) sample, an abrupt upturn appeared in the Mooney-Rivlin plot at high elongation. Such an upturn, however, was not observed for the SC sample, in which fewer entanglements exist. Furthermore, hysteresis phenomenon was not observed for the SC sample. This suggests that little or no strain-induced crystallization occurs even at high elongation for the SC sample. This was confirmed by comparing equatorial X-ray diffraction patterns and birefringences for both types of stretched samples. These experimental results for the SC sample were not due to a small amount of residual decalin; No effect of sorbed decalin was detected by stress-strain measurements in decalin atmosphere. Taking into account the entanglement effect on network structure, the relation between the network structure and mechanical properties for the two kinds of rubber samples was discussed.
Transient shear stresses in linear polystyrene solutions after stepwise change of shear rate from a steady shear rate γ1 to a higher or a lower values of γ2 were observed using a Weissenberg rheogoniometer type R-17. The initial parts of stress development curves after stepwise increase of shear rate from constant γ2 to different γ1 compose a single line independent of γ2. The initial parts of stress relaxation curves relative to the first steady state also compose a single line independent of γ2 if γ2 is kept constant. It was concluded that the original quasi-network structure of polymer solutions have a stability and in the case of stepwise increase of shear rate the original structure is ruptured when a certain critical strain is accumulated in the solution. It was also concluded that the initial slopes become lower with increasing γ1 reflecting decrease of the effective entanglement density with increasing γ1.
The penetration depth of a rod perpendicular to a surface of powder mass was measured by Yuasa et al. as a function of impulse of falling weight on top of the rod for beads of styrene resin and glass. Regarding to the measurements, the author derived a theoretical equation relating the potential energy of the rod and the friction of the powder. The equation shows that the penetration depth increases with increasing falling height and falling weight. The theoretical result seems to agree with the experimental results.
A new type of damped oscillation rheometer was developed for the study of biorheology. The rheometer consists of the cylindrical tube suspended from a torsion wire and filled with test liquid. The cylindrical tube may be made of various materials. The tube is excited in torsional oscillation and the subsequent damped oscillation is observed. The apparatus can sensitively follow the change of fluidity of liquid sample. Changes of logarithmic damping factor for blood and fibrinogen solution during coagulation were measured. The change of logarithmic damping factor for blood during coagulation remarkably depended on tube material, suggesting that the present method is probably available for in vitro evaluation of anticoagulability of artificial materials as well as for analysis of coagulation mechanism of blood.
Theoretical basis for a newly developed damped oscillation rheometer is presented for a Newtonian fluid. This rheometer essentially consists of a cylindrical tube suspended by a torsion wire and filled with fluid to be tested. The damped oscillation of the cylinder is observed. Based on some assumptions, the equations of motion for a Newtonian fluid in the tube are solved. The numerical solution and some approximate solutions valid for certain ranges of parameters are obtained. From these solutions the logarithmic damping factor and the period of oscillation are obtained as functions of fluid viscosity.