摘要:

AbstractThe theory of drop deformation in steady elongational flow is extended to the non‐steady elongational flow in a converging cone, Experiments with different fluid viscosities were carried out and compared with the theory, which is valid only for low deformations. The theory describes the drop deformation satisfactorily and under certain conditions even for higher deformations than expecte

ISSN:0032-3888    

DOI:10.1002/pen.760261802

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA simple expression is presented describing the volumetric throughput in a single screw extruder as a function of the pressure gradient with the dependence on the power law index included. Analytical expressions have also been developed for the optimum channel depth and helix angle for power law fluids.

ISSN:0032-3888    

DOI:10.1002/pen.760261803

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper presents a functional analysis of the advantages and disadvantages of several types of barrier section extruder screws, indicating preferred geometrical configurations for certain applications. In addition, aspects of barrier mixing sections are discussed and analytical expressions for optimizing channel depth and helix angle to minimize the pressure drop over the barrier mixing section are presented.

ISSN:0032-3888    

DOI:10.1002/pen.760261804

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractSolid state rolling of semicrystalline polymers represents a high speed process for producing oriented, high modulus films, tapes, and sheets. The important process variables include roll temperature, thickness of initial sheet, roll speed, take‐up tension, roll diameter, and initial morphological state of the polymer. Roll temperature controls both the extent of maximum deformation and the rate of rolling. A minimum temperature exists for each polymer below which the orientation process is sharply limited. This condition is similar to the limitation present in the hydrostatic extrusion process, in which the alpha crystallization temperature limits the orientation process. Roll speeds as high as 20 m/min have been realized. It is apparent that film thickness and thickness reduction ratio have a strong effect on the ultimate rolling rate. The process, as currently practiced, is adiabatic, and therefore, heat transfer limited. The take‐up tension influences the extant of orientation in the amorphous phse of of the polymer. This in turn affects its thermal and chemical stability. The effect of roll diameter is to limit the extent of thickness reduction by causing roll‐film slippage when the roll dianmeter to thickness reduction ratio is below some as yet undetermined value. The initial morphological state of the polymer affects the amount of crystalline deformation possible, the surface texture of the rolled film, and the tear resistant of the oriented

ISSN:0032-3888    

DOI:10.1002/pen.760261805

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper deals with computer simulation of the filling stage of the Reaction Injection Molding (RIM) process for cavities of rectangular, cylindrical, and disc shapes. The computer model is in two parts: the main flow and the flow by the moving front. In the main flow part, the transient equations of axial momentum, energy and species conservation and also the continuity equation are solved numerically by finite‐difference methods using a moving, changing mesh. In the flow front part, which is quite novel, the transient (parabolic) vorticity, energy and species conservation equations and the elliptic streamfunction equation are again solved by finite‐difference methods. An important feature of both parts is that convection along and across the flow is included in all the transient equations. Results are presented for all three cavity shapes and those for rectangular cavities are compared with the experimental results of previous investigat

ISSN:0032-3888    

DOI:10.1002/pen.760261806

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA study examining the molecular orientation of poly(dimethylsiloxane) for different combinations of elongational and shear strains is presented. Three different cases were studied: (1) pure elongational strain; (2) increasing shear and decreasing elongational strains; (3) increasing shear and increasing elongational strains. The experiments were performed in a converging flow cell (at room temperature), where elongational and shearing strain rates achieved values of 370 s−1and 640 s−1respectively. Values of the Hermans orientation function were obtained from measurements of birefringence and polarization angles while strain rates were estimated from laser Doppler anemometry velocity measurements. Prospects for predicting molecular orientation from the stress‐optical laws and rheological flow models are outlined and comment

ISSN:0032-3888    

DOI:10.1002/pen.760261807

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe pressure loss between the mold and the nozzle in the injection molding of bar and box moldings has been monitored. The pressure drop observed during filling of the mold is reduced during the packing stage but remains finite. This has been attributed in the literature to solidification of polymer across the cavity transducer and to melt relaxation phenomena. Experiments have been carried out with hot molds to prolong the packing stage at the expense of the ‘cooling’ stage. Under these circumstances the pressure drop is reduced but not eliminated. The observed pressure drop may be related to the viscosity of the melt and its dependence on pressure and temperature although strain‐induced crystallization and the pressure dependence of the melting point can confer effects similar to the cooling

ISSN:0032-3888    

DOI:10.1002/pen.760261808

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect of orientation on the brittle‐ductile transition in rolled polycarbonate was examined. It has been believed that the brittle‐ductile transition is governed by the residual stress at low reduction and the orientation at high reduction. But, our experimental results revealed that the brittle‐ductile transition is caused by neither the residual stress nor orientation. It is proposed that the brittle‐ductile transition may be ascribed to the morphological change which is produced during plastic deformation on

ISSN:0032-3888    

DOI:10.1002/pen.760261809

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760261801

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY