Digital image analysis (DIA) is applied to extract physical information from an image of high-order structure of polymers. DIA is applicable to analyze various pattern formation phenomena such as crystallization and phase separation. Various numerical operations in real and wave-number space make it possible to extract physical information unobtainable by other conventional methods such as light scattering experiment. DIA is useful for studying not only polymer systems, but also various materials such as liquid crystals, ceramics, metals, and biological systems.
In order to perform a behavior analysis of polymeric material in a mixer with oval or wing type rotors, it was necessary to find a theoretical solution of the pressure distribution in the material along the circuit direction of the rotor. We considered a behavior model in which the material flowed from a wide channel that tapered down into a narrow one corresponding to a space between the rotor and chamber of the mixer. Using this model, the pressure distribution throughout the whole circuit of the rotor was theoretically analyzed under the following two conditions: 1) the material behaved as a Newtonian fluid, 2) the material behaved as a non-Newtonian fluid of a power-law type. Through this analysis, the necessary theoretical solution for pressure distribution of the two types of fluids were obtained, and the theory of pressure distribution in a mixer was then completed. These analyses showed that the maximum pressure along the circuit of the rotor did not occur in the tip area, but rather at the front face of the rotor. They also showed that pressure distributions differred when all conditions except fluid type (Newtonian and non-Newtonian) were held constant. The pressure distribution curves, which indicated pressure increasing in the direction of flow at the front face of the rotor, were shown to be closer to linear for the non-Newtonian fluid than for the Newtonian fluid.
In a previous paper, the pressure distribution was theoretically analyzed for the original behavior model in which polymeric material flowed from a wide channel that tapered down into a narrow one, corresponding to a space between the rotor and chamber of an oval type mixer. In this paper, the theoretical analysis was compared with the results of experiments which used low density polythylene in a one rotor mixer. For a non-Newtonian fluid, the numerical solution agreed with experimental results in the case of a complete melt. However, agreement between theory and experimental results during the initial period of mixing was poor. The experiments showed that a layer of unmelted material remained on the rotor surface at the front face of the rotor. This gradually dispersed into the melt so that both solid and liquid phases coexisted within the flowing material. The original behavior model was modified to include the correct viscosity of the fluid with coexisting solid and liquid phases, as well as the correct angle between the chamber and the boundary of the unmelted layer. After the new behavior model was applied, analysis showed that the pressure distribution for the non-Newtonian fluid agreed more closely with the experimental results during the initial period of mixing. Furthermore, the experiments confirmed theoretical predictions that maximum pressure occurs at the front face of the rotor.
The force required to thrust a sewing needle slowly through a cloth was measured, and the results were discussed in relation to their correlation with the texture of the sample. In the initial stage, the needle point pushes up the cloth, without passing through it, into a conical shape. The force imposed on the needle is the recovery force of the deformed cloth, and hence depends on the elastic moduli as well as the geometry of the sample. At the moment when the needle point penetrates the cloth, the force goes rapidly down and then up gradually until the diameter of the needle at the contact portion reaches its maximum. In this process the recovery force of the cloth balances with, and hence equals, the frictional force that is generated on the contact area by the woven threads thrust away by the needle. Therefore the force of thrust at this stage may reflect some mechanical properties of the threads woven in the cloth, such as the lateral compressibility, the rigidity of local bend, and the stickiness at the crossing areas.
The viscoelastic properties of concentrated solutions of styrene-butadiene radial block copolymers have been measured to investigate the effect of temperature, shear history, length of branches, concentration, and primary structure. Block structure for the AM series examined was (B-S-)n and that or the MA series (S-B-)m, where n and m are about 11 and 8, respectively. The solvent used is partially chlorinated biphenyl (KC4), which is a good solvent for both the styrene block and the butadiene block. The frequency dependence curve of visccelastic functions for the MA series exhibits the so-called second plateau but that for the AM series does not. The rubbery plateau modulus GeN0 for the MA series is higher than that for the AM series. The experimental results on the rubbery plateau modulus are well explained by a concept proposed in this study. The molecular weight dependence for the characteristic time constant of entanglements ωb-1 of the AM series is remarkably higher than that of the outer chain of molecules for the MA series. The height of the second plateau of the MA series is proportional to (ωb-1 GeN0)0.24. The height of the second plateau for radial block copolymers having shorter length of branches is affected by temperature and shear history at low concentration.
Linear viscoelastic properties of binary blends of monodisperse polystyrenes (PS) with low (M1) and high (M2) molecular weights were examined. The relaxation modes of the longer chain component were strongly affected by its content ω2 as well as by the molecular weights of the components. In the blends with sufficiently small ω2, the longer chain (2-chain) entangled only with the shorter ones (1-chains). If M2 is sufficiently larger than M1, the 2-chain in such a dilute blend relaxed by Rouse-like modes : In the dilute blends with M1 less than the entanglement spacing Me0, the 2-chain relaxed by its intrinsic Rouse mode with the characteristic time τ2,Rouse∝M10 M22. In those with M2>>1>M10, the retarded Rouse-like modes of the 2-chain were observed and the characteristic time was proportional to M13M22. In the blends with large ω2, the 2-chain entangled with both 1- and other 2-chains. In such a concentrated blend with M2>>>M1>Me0, the 2-chain behaved in the long time region as if in a usual concentrated solution in a low molecular weight solvent. This indicates that the 1-2 entanglements become ineffective at intermediate time scales before the relaxation of the 2-chain completes. A detailed analysis on the storage and loss moduli of the 2-chain in the blends revealed that the constraints due to 1-2 entanglements are released at time scales being close to the characteristic time for the corresponding dilute blends (with the same M1 and M2), which in turn is longer than the intrinsic time τ2, Rouse.