An investigation of the flow, mechanical, tribological properties, such as tensile, bending, impact strengths, friction and wear rate was conducted for various blends of three polymers, namely, LCP (liquid crystalline polymer), PAR (polyarylate) and PA (polyamide).
The results were summarized as follows;
1) The tensile and bending strength of blends of LCP 25/75 PAR (LCP 25%, PAR 75%) was greater than that of neat PAR.
2) The frictional coefficient and wear rate of blends of LCP 25/75 PAR and LCP 25/75 PA were smaller than that of neat LCP, neat PAR and neat PA.
3) The dependence of frictional speed on the frictional coefficient and wear rate of blends approached to that of neat LCP with increasing of LCP content.

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The nature of viscoelastic flow near the exit of a nozzle is dependent die swell phenomena and various polymer processing operations such as fiber spinning, sheet forming, blow molding, etc. Although many calculations have been performed by various investigators, the local values of stresses have seldom been compared experimentally and numerically. In the present paper, the exit flow is analyzed by the finite element method. The constitutive equations used in the simulations are the Phan Thien-Tanner (PTT) type model of a viscoelastic fluid with shear thinning viscosity, the Oldroyd-B model of a viscoelastic fluid with constant viscosity, the power-law model of a pure viscous fluid with the shear thinning viscosity, and the Newtonian model. The stress distributions and swelling ratios are compared among these models, and the effects of shear thinning viscosity and elasticity on the exit flow are considered. It is found that swelling ratio decreases as the shear thinning effect of viscosity becomes stronger, and increases with the elastic effect. The swelling mechanism can be explained mostly from the viewpoint of stress. The calculated results of stress distributions by the PTT type model are compared with the experimental values measured by means of the flow birefringence technique. The stress distributions calculated are found to be in agreement with the experimental values, but the estimation of swelling ratio is insufficient.

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The effects of molding conditions on fiber orientation patterns were studied using X-ray diffraction. From an analysis of the diffraction patterns in the depth direction, it was determined that the plaque consists of three or four layers with different orientation patterns and thicknesses.
Preferential directions of fibers the outer two layers, namely, skin and intermediate, are independent of molding conditions. The skin layer is preferentially oriented transverse to the flow direction, while intermediate layer is highly parallel.
The patterns in the core layer can be classified into two different types. Type I, with transverse orientation, appears in a plaque under fast mold filling conditions. When the plaque thickness is over 1mm, a sub-layer appears near the intermediate layer, the thickness of this sub-layer decreases with increasing flow length. Type II shows the parallel orientation as opposed to that of type I and appears at a slower flow rate.

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The purpose of this paper is to describe a ball indentation test which can be used as a quick and easy method to measure of the Young's modulus of particle reinforced composites. First, the contact equations between a ball indenter and the specimen surface were studied using on Hertz's elastic contact theory. Second, the center's displacements of an indenting ball were carefully observed and an equation for calculating Young's modulus was obtained. Finally, good agreement was obtained between Young's moduli determined by uniaxial compression tests and ball indentation tests for four types of particle reinforced composites.

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The shrinkage of crystalline polymer products formed in injection molding is evaluated, on the assumption that the specific volume in polymers can be represented by Spencer-Gilmore's empirical equation, and compared with experiments. The values of the solid state parameters in Spencer-Gilmore's equation are estimated from thermal expansion and compressibility data, where the dependency of specific volume on die temperature is considered. The parameters for the melt state are determined using the results of specially designed injection moldings, which give the polymers very different temperature and pressure histories from each other. The mean specific volume can be represented with terms involving the integral of the specific volume along the thickness direction. If the time of gate seal and pressure change are measured, the mean specific volume can be calculated from this equation, where the temperature distribution of the polymer in die the cavity is simulated in the thickness direction. On the other hand the specific volume can also be obtained experimentally. Good agreement is obtained between the simulated and measured values for the mean specific volume and the shrinkage.

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The capillary flow of polymer melts is often accompanied by flow instabilities in the high shear stress region during polymer processing. In order to investigate these behaviors, a new capillary rheometer was developed by modifying an injection molding machine. The experimental results were as follows: (1) With an increase in shear stress, stable steady flow changed into unstable sharkskin flow at a critical shear stress σ_s·s., and then, into gross melt fracture flow at σ_m·f. At these critical shear stresses, both apparent viscosities and elasticities showed discontinuous changes. (2) In the case of sharkskin flow, the flow patterns in the longitudinal sections of the extrudates indicated that the cyclic turbulence in flow was limited only at the thin polymer-layer contacting the capillary wall, and stable laminar flow was maintained in the inner part. (3) During sharkskin flow in the capillary, slippage at the wall was observed. The slip-velocities decreased remarkably with an increase in the adhesive strength at the wall/polymer interface. (4) Considering these results, a model for the flow-mechanism of unstable sharkskin flow was discussed, and the calculated values of critical shear stresses agreed approximately with the observed values.

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