摘要:

AbstractA previously proposed but further modified theoretical model for melting in plasticating extruders, in the form of a computer program, which predicts the amount of unmelted polymer at any point in the extruder, was used to simulate the effect of geometrical and operating variables on the melting performance of the extruder. The results indicate in increasing screw length required to complete melting with increasing throughput and a decreasing length of melting with increasing frequency of screw rotation. They further indicate the existence of an optimum barrel temperature for a maximum rate of melting, an optimum number of threads for a maximum melting rate, and a significant decrease in the rate of melting with increasing flight clearance. The effect of other geometrical variables and of operating conditions on the rate of melting and power consumption are also discussed.

ISSN:0032-3888    

DOI:10.1002/pen.760090102

出版商:Society of Plastics Engineers, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractA fundamental mathematical model of the plasticating extruder was assembled by combining a previously reported melting model with an improved melt pumping model. The validity of the model was tested with numerous experiments on 2 1/2 in. and 8 in. diameter extruders. The experiments were performed with low and high density polyethylene, plasticized polyvinyl chloride, rigid polyvinyl chloride powder, polypropylene, ABS and nylon 66. The mathematical model proved to be excellent in predicting pressure and plastic temperature profiles in the extruder channel, temperature fluctuation, solids content, and power consumption.

ISSN:0032-3888    

DOI:10.1002/pen.760090103

出版商:Society of Plastics Engineers, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractMolten polymer was pumped through an isothermal‐wall heat exchanger and the temperature at four radial positions was measured with a hypodermic thermocouple. Temperature profiles were obtained for heating, cooling, and isothermal flow of polyethylene, polystyrene and polypropylene at Graetz numbers from 1.7 to 9.2. The results show large viscous heating effects, particularly for coolin

ISSN:0032-3888    

DOI:10.1002/pen.760090104

出版商:Society of Plastics Engineers, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe melt flow behavior of straight emulsion‐polymerized PVC in a capillary extrusion rheometer has been found to depend upon both the molecular weight and the particle size of the sample. Observations of flow‐rate, post‐extrusion swell, and extrudate appearance, as functions of extrusion temperature and pressure, suggest that both molecular deformation and particle slippage are involved in the flow mechanism. The relative importance of these two modes of flow varies with extrusion conditions and with the PVC molecular weight and particle size. Particle slippage is favored by large particle size, high molecular weight, and low temperature and by a shear stress above a critical yield value. Apparent melt viscosity, swelling, and roughness are minimized under conditions corresponding to the maximum contribution of particle slippage. In the proper range of temperature and shear rate, straight emulsion PVC yields smooth, low‐swell extrudates of excellent physical pro

ISSN:0032-3888    

DOI:10.1002/pen.760090105

出版商:Society of Plastics Engineers, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThe validity of the Busen‐Roscoe reciprocity law in flash exposed dichromate sensitized polyvinyl alcohol (PVA) films was investigated. It was found that the flashlamp operating conditions were an important parameter in an exposure system, since a spectral distribution shift of the lamp output could be obtained by changing the pulse duration from 0.3 to 2.0 msec. The apparent reciprocity failure obtained by varying the pulse duration while maintaining the energy stored in the capacitor bank fixed was consistent with the spectral distribution shift in the lamp output. When this shift was accounted for there was only a negligible reciprocity failure found over the range of these flash exposures; however, comparison with a steady mercury are lamp showed that the flash exposure cross‐linked the PVA about 200 times more efficien

ISSN:0032-3888    

DOI:10.1002/pen.760090106

出版商:Society of Plastics Engineers, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractA new photoredox catalyst is described wherein a phenothiazine dye in its excited state oxidizes a catalyst to a free radical. This free radical efficiently initiates the polymerization of metal acrylates giving rise to polymers which are insoluble in the monomer‐containing medium. The polymers precipitate as insoluble colloidal particles. Optical transmission measurements are used to follow the polymerization and to calculate the number and size of the polymer particles. The effect of various factors such as the nature of the catalyst and the photooxidant, the pH and the temperature of the medium on photopolymerization are described. It is indicated that this new system may be useful for rapid photographic imaging and display application

ISSN:0032-3888    

DOI:10.1002/pen.760090107

出版商:Society of Plastics Engineers, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractPolymer pellets are frequently melted on a melting grid. The melting capacity of the gird depends on the force with which the bed of pellets is pressed against the grid bars and on the difference between the temperature of the grid bars and the melt temperature. In this investigation, this dependence has been examined, theortically as well as experimentally, for the case where the pellets melt on the top of the grid. Agreement with the theory was found.

ISSN:0032-3888    

DOI:10.1002/pen.760090108

出版商:Society of Plastics Engineers, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThis paper is the third in a series describing work done under Air Force sponsorship to develop high temperature polyimide laminates for radomes and other parts for supersonic aircraft.Twelve resin compositions are described and evaluated. Most were prepared from benzophenonetetracarboxylic dianhydride and one or more aromatic diamines. Modifying linkages such as amide, ether, benzimidazole, and oxadiazole were present in some cases.A variety of precure and pressing conditions were studied, best results being obtained with a fully cured prepreg pressed at about 700°F and 200–1000 psi. Most of the laminates were made with E glass cloth, but some work was done also with S glass, Refrasil, and carbon cloth.Initial flexural strengths on E glass of 35–60,000 psi at room temperature, and 20–40,000 psi at 600°F were observed for the better resins. On S glass, slightly higher strengths were observed together with values of about 10,000 psi at 700–1000°F. Aging data on E glass laminates show retention of at least 10,000 psi flexural strength at temperature for about 250 hrs. at 650°F, 1000 hrs. at 600°F, 5000 hrs. at 527°F, and 30,000 hrs. at 482°F.Dielectric constant and dissipation factor at 10 Gc were found to be nearly constant at 3.5–4.4 and 0.005–0.01, respectively, for temperatures up to 662°F and for aging up to 1000 hrs. at 600°F. At frequencies of 60 c and 1 Kc, an increase of dissipation factor with temperature was found and was us

ISSN:0032-3888    

DOI:10.1002/pen.760090109

出版商:Society of Plastics Engineers, Inc.    

年代:1969

数据来源: WILEY

摘要:

AbstractThis study was undertaken in order to understand the effect of low molecular weight additives on the visco‐elastic properties of polymers and, in particular, Diamond Shamrock Corporation's PVC‐40 resin. The viscous response has been reported in Part I of this series (11). This report describes the elastic properties of these mixtures.A new theoretical analysis of elastic response has been formulated. The direct calculation of stored elastic energy from capillary rheometer measurements is now possible.The conclusion drawn from both the viscous and elastic response study is that a change in viscosity is not a necessary nor sufficient condition for improved processability. Increased flow is obtained by lowering the viscous losses, but the melt fracture phenomena may be unchanged. In order to completely characterize the compound, both viscous and elastic response must be measu

ISSN:0032-3888    

DOI:10.1002/pen.760090110

出版商:Society of Plastics Engineers, Inc.    

年代:1969

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760090101

出版商:Society of Plastics Engineers, Inc.    

年代:1969

数据来源: WILEY