The basic rheological properties of glass fiber filled polypropylene melts were studied by shear flow and elongational flow methods. Shear viscosity, the first and second normal stress differences in shear flow, elongational viscosity, die ends pressure losses, and extrudate die swell are discussed. Glass fibers increase shear viscosity and normal stresses, with the greater increase being for the latter property. This effect can be shown clearly by plotting φ1/2η for shear rate γ, where φ1 is the first normal stress coefficient and η shear viscosity. The presence of glass fibers substantially increases elongational viscosity χ at low elongational rates but χ decreases rapidly at high deformation rates. The ratio of die ends pressure losses to shear stress, Δpends/(σ12)w, i.e., the Weissenberg number., is significantly increased with increasing the contents of glass fibers, but the extrudate die swell B is substantially reduced by the presence of glass fibers. Consequently, these rheological properties except extrudate die swell are caused by the large Weissenberg effect induced by glass fibers.
Dispersing and rheological properties of ZnO-Fe2O3 mixed suspensions were studied under various conditions of dispersing media, particle number ratios, and means of mechanical agitation or peptization prior to the measurements. When the total solid content was kept constant, the sedimentation volume Vs and the parameter αβ, calculated by applying Casson's equation to flow curves, varied in parallel to each other with varying volume fraction of Fe2O3 in the dispersing phase m and showed maxima at a certain value mm. These maxima were most remarkable when aqueous solution of Na4P2O7 was used as medium which showed the highest dispersibility for each single component. The value of mm was closely related to the particle number ratio, 1:1. When the mechanical agitation or mixing was insufficient, the maximum in Vs was much less remarkable or disappeared even in Na4P2O7 solution.
A new apparatus has been designed for study on rheo-optical properties of liquids and liquid crystals. A usual cone and plate type rheometer, equipped with a transparent cone and plate made of quartz is combined with an optical system: A monochromatic laser light beam is introduced successively to a polarizer, a quartz plate, a sample, a quartz cone, and an analyzer, and finally the transmitted light is detected by a photomultiplier tube. Thus the optical system enables us to measure the transmitted light intensities of polarized light through the sample under shear deformation. Measurements have been performed on solutions of poly (γ-benzyl glutamate) in m-cresol of concentrations below A-point (i.e., in isotropic state) at room temperature (20°C). The shear stress and the transmitted light intensities (I×, I″, and IE) have been measured simultaneously as a functions of steady shear rate (2×10-2~102s-1), where I×, I″, and IE are, respectively, the transmitted light intensities under crossed polarizers, under parallel polarizers, and under crossed polarizers at extinction position. At high shear rates, quantities I″ and IE vary in a wavelike manner with alternating maxima and minima with increasing shear rate. However, the quantities I×+I″ and IE are independent of shear rate. Thus the variation of I× and I″ is considered to arise from the continuous retardation change of the system with increasing shear rate, due to the increase in orientation of the rod-like macromolecules. The change of I× or I″ begins to be remarkable at a certain critical shear stress, where the viscosity begins to decrease noticeably with increasing shear rate. The critical shear stress was independent of the concentration. The birefringence of the system under. shear is also evaluated from the I× and I″ data in terms of socalled transmission method.
The viscoelastic properties of melts and concentrated solutions of styrene(St)-methyl methacrylate(MMA) block copolymers were measured. The experimental results were compared with earlier results for the component homopolymers, polystyrene (PS) and poly-(methyl methacrylate) (PMMA). The main conclusions obtained in this study are as follows: (1) The entanglement modulus G0eN of St-MMA block copolymer is independent of the molecular weight, as is for PS. (2) In the iso-free-volume state, the zero-shear viscosity of St-MMA block copolymer is lower than those of PS and PMMA at the same molecular weight. (3) The steady-state compliance of St-MMA block copolymers and their solutions depends on molecular weight even in the entanglement region. This behavior is similar to that of PMMA. (4) The steady-state compliance of St-MMA block copolymer is proportional to c-2 at relatively high concentrations, as is for the ordinary linear polymer liquids.
In the flow of powder from a hopper with an inclined open channel, the flow rate increases as the opening height of the hopper outlet increases, and the increasing ratio of the flow rate diminishes suddenly as the outlet opening exceeds some critical height. This behavior of the powder flow is interpreted in terms of a powder model in which the powder consists of homogeneous spherical particles and the frictional force is proportional to the height of the moving mass. The powder pressure at the outlet is assumed to be constant. The force balance between the powder pressure and the frictional force defines a critical opening height of the outlet. The flow rate increases monotonously with increasing height h of the outlet until h attains the critical value Hf. When h exceeds Hf, the increase in h does not contribute to further increase of the flow rate, but leads to a stationary mass beneath the moving layer.
Relaxation moduli G(t) of aqueous gels of amylose, amylopectin, and their blends were measured at various magnitudes of shear strain s with a relaxometer of the cone and plate type. The magnitude and the shear strain dependence of G(t) for amylose gels which are regarded as crystalline gels were markedly affected by the rate of cooling: The higher the growth of crystallites as coupling points of network structure, the longer the linearity of viscoelastic properties persisted. The relaxation behavior of amylopectin gels depended on the magnitude of s. However, the non-linearity was not so peculiar compared with that observed for other concentrated polymer solutions. By adding amylose to amylopectin, the relaxation modulus of gels was remarkably enhanced, and the nonlinear behavior became observable in the range of very small shear strain (0.05<s<0.5).
The first normal stress difference of polymer melts has often been obtained from the exit pressure by assuming that the flow at the exit of the nozzle is fully developed. This assumption, however, is not rigorously fulfilled as shown by several experiments. In this paper, one means for avoiding this assumption was presented: the circumferential Poiseuille flow through an annulus was analyzed by approximating the shear stress distribution in a simple polynomial. The equations of the flow curve and the first normal stress difference were derived. The first normal stress difference was found to be obtained from measurement of the difference in radial pressures at cylindrical surfaces. This pressure difference was roughly estimated to be smaller than the first normal stress difference by one order.