摘要:

AbstractFountain flow is the phenomenon of deceleration and outward motion of fluid particles as they approach a slower moving interface. The use of a general purpose finite element program for the appropriate boundary conditions made possible the detailed flow description behind an advancing liquid front moving at constant speed inside two‐dimensional channels and tubes. The results were qualitatively the same for both Newtonian and shear‐thinning flu

ISSN:0032-3888    

DOI:10.1002/pen.760260702

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA theoretical study has been carried out of the two directional isothermal flow of two molten polymers in a flat die. The viscous behavior of each fluid is described by a power‐law. Using an iterative finite difference method, a numerical program predicts the influence of geometrical and Theological parameters on the variations of the interface position. Theoretical values are in good agreement with experimental results obtained on a fish‐tail die. In the case of a coat hanger‐die, the mean value of the interface position is correct, but the general shape may be quite diff

ISSN:0032-3888    

DOI:10.1002/pen.760260703

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractCast polymer films are extruded through a uniform thin slit onto a quench roll. Between the die and the quench roll, thick edges called edge beads form, which have to be trimmed from the film, and are often scrapped. The relation between edge beads and neck‐in is shown. Three causes of edge beads are discussed: surface tension, die swell, and an edge stress effect. Surface tension and die swell effects can be important in low viscosity and elastic materials respectively. The predominant cause of edge beads is an edge stress effect which occurs because the film is stretched between the die and the roll. The edge elongates in uniaxial stress while the center material elongates in plane strai

ISSN:0032-3888    

DOI:10.1002/pen.760260704

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractIn the application of plastic pipes for fluid transport and for the protection of underground electrical cables, it is desirable to improve mechanical properties, particularly in the hoop direction. The use of orientable reinforcing particles such as chopped glass fibers could make possible such an improvement if the orientation of the fibers could be controlled. While conventional pipe extrusion dies tend to promote axial fiber orientation, the use of an expanding channel die has been proposed to produce a preferential hoop orientation of fibers. In this paper, a theoretical model of the flow of a fiber suspension through an expanding channel die that predicts the fiber orientation distribution at the die exit is described. The effects of Theological properties and die geometry on the final fiber orientation distribution are predicted. The results of an experimental study of fiber orientation in pipe extruded using an expanding channel die are shown to be in agreement with the theoretical predictions.

ISSN:0032-3888    

DOI:10.1002/pen.760260705

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of drawing temperature and the presence of various types of additives on gamma and ultraviolet radiation induced oxidative degradation of high density polyethylene have been studied. Uniaxial drawing of the polymer was conducted at 60, 80, and 100°C. The additives were an antioxidant, light stabilizer, and carbon black, used in various combinations, Oxidative degradation was followed from carbonyl formation by IR spectroscopy. It is found that at a given draw ratio, the oxidative degradation is retarded when the drawing temperature is increased, irrespective of whether or not the polymer contains any additives in any combination. This is due to the decrease of the surface and/or bulk microcracks formed during the drawing process at high temperature. Carbon black/antioxidant mixtures were shown to be antagonistic, while a carbon black/light stabilizer mixture resulted in a synergetic effect in drawn or undrawn materials

ISSN:0032-3888    

DOI:10.1002/pen.760260706

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect of fill time on the mechanical properties, surface appearance, and part dimensions of several polymers was determined. Two crystalline materials, polypropylene and nylon 6,6, and an amorphous material, acrylonitrile‐butadiene‐styrene (ABS), were used. In addition, the effect of the presence of glass fibers was examined using glass fiber reinforced nylon 6,6. The fill time was varied from 0.8 to 20 sec which included both the viscous flow controlled region (short fill times) where laboratory samples are ordinarily molded and the heat transfer controlled region (long fill times) where production parts arc commonly molded. No large variations in tensile properties were observed for polypropylene or nylon, but a 10 percent increase in peak tensile stress and strain for ABS did indicate that molecular orientation increased with increasing fill time. However, significant differences did occur in the properties of glass reinforced nylon. Peak tensile stress increased 15 percent and flexural strength decreased 10 percent as the fill time was increased. Although no change in the flexural modulus was observed, the scatter in the modulus decreased with increasing fill time. These property variations can be attributed to differences in the glass fiber orientation of the skin and core regions of the part. The measurement of molded tensile bar dimensions indicated there was little effect of fill time on the shrinkage of the various polymers except for shrinkage in the length direction for polypropylene. The shrinkage increased from 13 to 15.4 mm/m over the fill time range, a great enough difference to affect the fit of large parts. The most dramatic change with fill time was the surface appearance of the glass reinforced nylon. The surface of samples molded at short fill times had a dark uniform color and smooth appearance while samples molded at long fill times had a lighter color and a porous surface. This surface porosity is due to crystallization prior to complete pressurization of the mold. Therefore, in addition to affecting surface appearance, other surface related properties such as aging and the ability to plate plastic parts could also be affec

ISSN:0032-3888    

DOI:10.1002/pen.760260707

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe multiobjective nature of optimization problems related to homopolymerizaton and copolymerization processes implies a vector objective formulation for a correct approach. Two copolymerization systems, methyl methacrylate‐vinyl acetate (MMA‐VA) and styrene‐acrylonitrile (ST‐AN) are simulated, and some aspects of the steady state optimality of continuous operation are analyzed. The determination of non‐inferior sets through the concept of Pareto optimality permits a clear decision on trade‐offs related to operating conditions and product spe

ISSN:0032-3888    

DOI:10.1002/pen.760260708

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractAn experimental study was carried out to study and characterize the capillary extrudate swell and parison swell behavior in extrusion blow molding of two commercial blow molding grade high density polyethylene resins. The capillary extrudate swell behavior of these resins were determined employing a capillary rheometer and a special thermostatting chamber. Parison swell behavior was determined using an Impco A13‐R12 reciprocating screw blow molding machine in conjunction with cinematography and pinch‐off. The experimental conditions under which capillary extrudate and parison swell data can be related are elucidated. Excellent agreement is found between the area swell values determined on the basis of capillary and parison swell experime

ISSN:0032-3888    

DOI:10.1002/pen.760260709

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760260701

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY