摘要:

AbstractA theory for roll coating of a fluid onto a moving sheet is developed utilizing the usual “lubrication approximations.” The effects of fluid and operating parameters on coating thickness and pressure distribution are determined for a Newtonian fluid, and for a purely viscous non‐Newtonian fluid obeying the Power Law. The results for these cases are obtained analytically, and are rather straightforward.A viscoelastic fluid is considered, of a type which shows typical non‐Newtonian shear behavior observed in polymer melts and solutions and which also exhibits normal stress behavior. Analytical solutions are not possible, but a perturbation method, using a viscoelastic perturbation parameter related to a Deborah number, yields an approximate solution. Only terms to first order in the perturbation parameter are given. Subject to that degree of approximation, the following conclusions are drawn:1Non‐Newtonian shear behavior reduces the pressure distribution, and increases the coating thickness.1Elasticity of the type usually observed in polymer solutions makes only a minor contribution to the roll‐separating (load‐carrying) force. The contribution is positive, but smaller than the corresponding negative contribution due to the non‐Newtonian shear effects.1An increase in load‐carrying capacity would require a different viscoelastic fluid than the type considered here—one that is essentially Newtonian in shear but, independently, capable of developing signific

ISSN:0032-3888    

DOI:10.1002/pen.760150102

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractLiquid SO2sealed into tubes made of a fluorocarbon copolymer permeates the walls of the tube at a temperature‐dependent but accurately reproducible rate. Sulfur dioxide dispensers made in this way are called permeation tubes and are useful for calibrating instruments that measure SO2concentrations in air. The National Bureau of Standards calibrates SO2permeation tubes and makes them available as Standard Reference Materials. The permeation rate in a batch of nominally identical tubes varies enough that each Standard Reference Material tube must be individually calibrated. Changes in the length or radial dimensions of the tubes are much too small to explain most of this variation. An excellent (negative) correlation is found between the measured permeation rate and the density of the polymer (or weight per unit length). Since both the measured density and the permeation rate for this semi‐crystalline polymer depend upon morphological factors, but in different ways, x‐ray diffraction measurements of the thickness and orientation of the lamellar crystals were made and a mathematical model was set up to identify the morphological factors which can cause variations in the permeation

ISSN:0032-3888    

DOI:10.1002/pen.760150103

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractHolographic interferometry was investigated as a method for nondestructive testing of flat sheets of glass‐fiber reinforced plastics. Initially, the deformation behavior of faultless sheets was examined by means of holographic interferometry. The interferograms which resulted from various loading conditions (i.e., tensile load, bending) were compared to results obtained mathematically. The interferograms of faultless sheets were then compared to those of defective laminates. By suitable loading of the smaples a range of laminate faults could be readily and qualitatively detected. The influence of these faults on the tensile strength was examined. Not only the mechanical loading of the laminates, but also an acoustic stimulation of the sheets proved suitable for interferometric detection of laminate fault

ISSN:0032-3888    

DOI:10.1002/pen.760150104

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThere are two distinct solid conveying theories that can be applied to plasticating screw extruders. One is Darnell and Mol's theory based on a solid‐to‐solid friction model and the other is Chung's theory based on a viscous shearing model. The two theories predict very different solid conveying performances for a same set of conditions. In this paper, the maximum pressures that can be developed inside plasticating screw extruders by the solid conveying force are calculated using each of the two theories. Comparison of the results may shed some light on the applicability of each theory for a particular extrusion operat

ISSN:0032-3888    

DOI:10.1002/pen.760150105

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractTensile properties of a poly(2‐hydroxyethyl methacrylate) (PHEMA) network filled with various amounts of glass beads, in the dry and the equilibrium water‐swollen states, have been studied below and aboveTg. The temperature ranged from 5° C to 170° C and the volume fraction of the filler was up to 50 percent. In the glassy region it has been found that the temperature at which the transition from brittle to ductiel behavior occurs is increased by the presence of the filler. In the brittle zone the strength of the composites is decreased by the presence of the filler and can be predicted by using a finite element method; in the ductile zone, however, the strength of the composites reaches that of the unfilled polymer.In the rubbery region failure envelopes have been obtained for both dry and swollen PHEMA/glass bead composites. Using a double shift procedure all the data have been superimposed to obtain universal failure envelopes for the two different states. The dependence of the shift factors on filler content is disc

ISSN:0032-3888    

DOI:10.1002/pen.760150106

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractEvidence is presented that singlet oxygen may have an important role in the photo‐oxidation of polymers. Increased attention is being paid to singlet oxygen as a possible reactive intermediate in the initiation step of the photodegradation of polymers. Singlet oxygen may be produced by energy transfer either from impurities or internal groups after excitation, e.g. carbonyl groups, which are present in commercial polymers. As a consequence, reactions of singlet oxygen may also be important in the stabilization of polymers, e.g. leading to search for new and more effective antioxidant

ISSN:0032-3888    

DOI:10.1002/pen.760150107

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe hydrodynamics of the filling of a rectangular mold cavity by a molten polymer is considered in terms of lubrication theory. Both isothermal and nonisothermal mold filling are analyzed. The relationship of the velocity field to the cavity geometry and temperature dependence of the rheological properties is predicted. Increasing the activation energy of viscous flow increases the tendency for channeling of melt through the center of the cavity. The results are compared to the experimental observations of our previous studies.

ISSN:0032-3888    

DOI:10.1002/pen.760150108

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA second‐generation apparatus was built and used to inflate heat‐softened plastic sheets to shapes from hemispheres to large spheroidal bubbles. Three sheet materials, polystyrene, high‐impact polystyrene, and cellulose acetate butyrate, were successfully formed beyond the hemispherical shape at temperatures somewhat below industrial levels. Four others, rigid poly‐(vinyl chloride), an acrylic‐modified PVC, cast poly(methyl methacrylate), and polycarbonate, could not be deformed beyond the hemispherical shape without rupture. Measurements included bubble profiles, thickness distributions and local extension ratios for the final bubbles; two plots of profile growth measured from high‐speed motion pictures; and a continuous record of bubble temperatures and blowing pressure from which the meridional temperature distributions were plotted.Fifteen bubbles were measured and analyzed. Profiles and extension ratios were compared with those computed from the equations of isotropic, isothermal elasticity, using several different strain‐energy functions with constant material parameters. Agreement over all fifteen bubbles on all properties was about ±10.8 percent (absolute) for the best models considered. Bubble growth occurred over periods of 5 to 8 seconds, with about 90 percent of the final area of the larger bubbles being generated in the final 1.5 seconds. The maximum areal elongations obtained were 18,600 percent for clear polystyrene at 238°F, 14,300 percent for high‐impact polystyrene at 224°F, and 1,010 percent for cellulose acetate

ISSN:0032-3888    

DOI:10.1002/pen.760150109

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760150101

出版商:Society of Plastics Engineers, Inc.    

年代:1975

数据来源: WILEY