摘要:

AbstractTwin‐screw extruders are used very effectively, when partially filled, for mixing and surface renewal of high‐viscosity fluids. The rate of energy input, often sufficiently high to be a major design consideration, determines the drive power, the heat input to the fluid, and the cooling requirements. Operating limitations may be fixed by thermal degradation of the material being processed. A simple model for the rate of energy dissipation in twin‐screw extruders predicts that the power input is proportional to the square of the screw speed. Measurements were made of shaft torque and screw speed for polyisobutylene passing through a large twin‐screw extruder having co‐rotating shafts. The experimental procedure avoids the problems of changes in holdup and temperature that accompany changes in screw speed under steady state conditions. The power input was found to be proportional to the screw speed raised to the exponent 1.90. This result was attributed to slightly pseudoplastic behavior of the fluid in the radial c

ISSN:0032-3888    

DOI:10.1002/pen.760261402

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe steady state structure of non‐isothermal free radical solution polymerization in a continuous stirred tank reactor is analyzed. With mean residence time as a bifurcation parameter, five regions of steady states are identified. The effect of reactor operating conditions on the structure and the stability of steady state is discusse

ISSN:0032-3888    

DOI:10.1002/pen.760261403

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA systematic, experimental study was conducted on the elementary process of devolatilization (DV) and the various parameters affecting it, using a specially designed apparatus, which is devoid of the flow complexities present in industrial equipment and which permits independent control of all pertinent parameters. The device simulates a flow configuration present in all rotating machinery used in DV, viz. the rotating melt pool. Parameters studied include exposure time, agitation rate, surface‐to‐volume ratio, melt viscosity, vapor pressure of volatile contaminant, applied vacuum level, concentration level of contaminant, and addition of inert substances for DV enhancement. The results of most parametric studies are presented here, but some will be published in a subsequent paper. All feed and product contaminant levels were analyzed using gas chromatogra

ISSN:0032-3888    

DOI:10.1002/pen.760261404

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA rheological analysis is proposed on a non‐conventional, constant pressure, non‐isothermal rheometer. The test usually starts with a polymer powder and ends with melt extrudate. The volume‐ (or displacement of plunger) temperature curve of the test is analyzed according to the following model: (1) at a temperature below the glass transition temperature, the test is related to the packing and/or compaction of powders, and also the compressive deformation of powders; (2) as the temperature is raised to where polymer flow begins, the test is analyzed according to melt viscous flow. The activation energy of flow of a polymer may also be estimated using this rheometer. Comparison and correlation of data using other techniques (e.g. torsional pendulum dynamic measurement, capillary rheometer, Rheometric dynamic spectrometer) will also be disc

ISSN:0032-3888    

DOI:10.1002/pen.760261405

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe structure which results from solid state extrusion using biaxial orientation is analyzed for oriented polypropylene. Structural changes on the spherulitic, lamellar, and macromolecular level during orientation are investigated using optical microscopy (OM), small angle X‐ray scattering (SAXS), and wide angle X‐ray scattering (WAXS). The results show that polypropylene spherulites undergo stepwise biaxial affine deformation and deform homogeneously into a disc‐like morphology. During this spherulitic flattening process, lamellar rotation into the planar direction occurs prior to lamellar break‐up at a baxial draw ratio of about 1.5. On the macromolecular level, the crystalline c‐axis orients in the plane concurrently with the lamellar break‐up, while the crystalline b*‐axis gradually orients normal to the plane. Amorphous chains are also oriented preferentially in the plane of deformation. A hierarchical model is proposed to illustrate the nature of the orientation in the flattene

ISSN:0032-3888    

DOI:10.1002/pen.760261406

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA comprehensive study of polyethylene extrusion was carried out with an instrumented extruder on several screws differing in geometry and paralleled with capillary rheometry of the extrudate leading to melt viscosity and elasticity functions. Assuming Oldroyd's constitutive equation for molten polyethylene and the extrudate melt temperature oscillation (ΔTm) as a measure of the process stability and an indication of melt mixing quality, it was found that the product of the dimensionless numbers (Deborah,Deand Brinkman,Br) correlates well (r= 0.93) with ΔTm. Since theBrandDegroups follow from the rheological characteristics of the melt and the extrusion process parameters, a relationship of type: ΔTm= a + b (De) (Br) appears useful in designing an extrusion process (for a polymer of known rheology) with respect to its stability, and indirectly, its mixing efficien

ISSN:0032-3888    

DOI:10.1002/pen.760261407

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe kinematics of ideal welding flows generated by a thin‐plate divider, a cylinder, or a slab in a slit channel are studied by using a finite element analysis. The analysis includes simulations of Newtonian and Carreau fluids. There are two flow configurations. First, a single plate‐divider or an obstacle was positioned symmetrically in a slit channel with no‐slip at the walls. In the second, an infinite number of plate‐dividers or obstacles were positioned in parallel, and the boundary walls were infinitely far away. It was found that extensional flow dominates the region near the stagnation points of obstacles and plate‐dividers, and that the fluid elements near the weld interfaces have a strain history of both high stretching and shearing. The thickness of the elongated region is reduced as the thickness of the plate‐divider increases. Shear‐thinning tends to increase the rate of extension. However, its influence on the flow field tends to lessen as the width of the flow channel or the obstacle size increases. A no‐slip condition at walls causes slightly stronger elongational flow in the weld interface than does the symmetric condition of perfec

ISSN:0032-3888    

DOI:10.1002/pen.760261408

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760261401

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY