摘要:

AbstractTurbulent flow in the impingement mixing head of a reactions injection molding machine produces a laminated mixture, whose striations are mostly so thick that any subsequent copolymerization would be hindered by diffusion. However, further reduction in striation thickness occurs during laminar flow through the runner. This is calculated here and is a function of the radial position in the runner and of its length/diameter ratio. So, for example, whenL/D= 10, it is predicted that at least 79 percent of, the reagent striations would be thin enough to permit reaction under kinetically controlled conditions.

ISSN:0032-3888    

DOI:10.1002/pen.760250102

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA general‐purpose finite‐element program has been used to simulate the flow of Newtonian, power‐law, and viscoelastic fluids in calendering. The analysis is fully two‐dimensional and does not make use of the lubrication approximation. Isothermal and nonisothermal calendering is studied and the results are compared with predictions from the lubrication approximation. The free surface is determined and circulatory flow patterns are predicted in the melt bank. Detailed calculations have been performed for a rigid poly(vinyl chloride) (PVC) resin that exhibits slip at the wall using rheological data for the melt and machine parameters. The results include determination of the shape and location of the free surface, vortex patterns, temperature and pressure distributions, and predictions of roll‐separating force, torque, and power consumption. Comparisons are made with experimental data available in the l

ISSN:0032-3888    

DOI:10.1002/pen.760250103

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractIn this study the effect of processing variables upon the optical properties of an injection‐molded thermoplastic polyurethane were investigated. The investigation was separated into two phases. The first phase used conventional experimental methods, the second phase used a central composite factorial design. The processing variables studied were: melt temperatures, tool temperature, injection speed, injection pressure, back pressure, screw speed, cushion size, and cycle time. The optical responses used to evaluate the processing variables were: percent haze, percent luminous transmittance, and line of sight deviation. Each of the significant parameters used was found to have some effect on at least one optical property. Statistical analysis showed interaction among the processing parameters, indicating that simultaneous control of the parameters was required. Empirical models were derived to predict responses for a given set of processing conditions. There was good agreement between the models and experiment

ISSN:0032-3888    

DOI:10.1002/pen.760250104

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractIf the tetraethylorthosilicate (TEOS) used to end link hydroxyl‐terminated poly(dimethylsiloxane) chains is present in excess, there are two effects on the resulting network structure. First, some of the excess TEOS hydrolyzes to givein situprecipitation of reinforcing silica particles. In addition, some can cause extension of the polymer chains, particularly of the shorter chains in the case of a bimodal network. In the present investigation, the ultimate strength and toughness of such bimodal networks was found to go through a maximum with increase in the amount of excess TEOS used in the curingfilling procedur

ISSN:0032-3888    

DOI:10.1002/pen.760250105

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractInteresting phenomena were observed in the polymerization of styrene and ethylene oxide into PEO‐PSt‐PEO triblock copolymers using potassium naphthalene as initiator and tolusene as a solvent. The relationship between the phenomena and molecular weight of the blocks was studied. The purified and characterized triblock copolymer showed mesomorphic behavior in toluene solution which depolarized polarized light increasingly as the concentration was increased. The structure of the triblock copolymer was also studied by small‐angle laser light scattering and by electron micro

ISSN:0032-3888    

DOI:10.1002/pen.760250106

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760250107

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe simulation of tubular, high‐pressure low‐density polyethylene reactors is performed using a comprehensive kinetic scheme which includes branching reactions as well as reactions leading to vinyl and vinylidene group formation. The variation of the physical properties of the reaction mass with position has been accounted for. In addition to predicting the conversions of the monomer and initiator, the temperature, and the number‐average molecular weight, this study enables the computation of the polydispersity index and the concentration of vinyl, vinylidene, and methyl groups as a function of position. These have important implications in terms of product properties. Detailed simulations have shown that the steady‐state approximation can be used for obtaining the concentrations of the initiator and the polymer radicals. In addition, some simple closure conditions have been established. The effect of multiple intermediate feeds is also investigated and it is found that under certain operating conditions the reactor performance becomes inherently u

ISSN:0032-3888    

DOI:10.1002/pen.760250108

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractMeasurements have been made of the recovery of polyethylene samples from bending deformations of varying severity. The amount of spring‐back from a severe bend is quite different for different densities (degrees of crystallinity), especially at short times after release, being much greater for lower‐density polyethylenes. Short‐term spring‐back measurements thus afford a simple and rapid means of determining the approximate density. Immediate recovery is small, 5 to 15 percent, and is in rough accord with expectations for elastic‐plastic solids. A major protracted recovery process follows. It is accelerated by raising the temperature, in reasonable agreement with the WLF relation for segmental mobility. It is therefore attributed to retarded molecular motions in the amorphous fraction. Final recovery is greater for lower‐density materials, but it is incomplete even after very long times or for mild degrees of bending. Thus, some irreversible processes appear to take place, even when bending strains as low as 3 percent

ISSN:0032-3888    

DOI:10.1002/pen.760250109

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractUnsaturated polyesters were prepared by one‐stage melt condensation of maleic anhydride, phthalic anhydride, propylene glycol, and poly(ethylene glycol)s with different molecular weight, and the properties of their castings from styrenated resins were investigated. Tensile and flexural properties decrease with the increase of molecular weight of poly(ethylene glycol), but impact strength, elongation, and water absorption have an inverse effect. This study improves the understanding of the effect of chain length of poly(ethylene glycol) in unsaturated polyester on the properties of its casting

ISSN:0032-3888    

DOI:10.1002/pen.760250110

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA detailed mathematical model for absolute particle‐size distribution in continuous emulsion polymerization of styrene monomer is proposed on the basis of the modified population‐balance theory. The computer simulation is then performed for styrene polymerization as an example of a nondesorption system. The effects of emulsifier and initiator concentrations as well as mean residence time on the absolute particle‐size‐distribution function, total concentration of polymer particles, conversion, average number and weight radii, average number of radicals per polymer particle, and polydispersity of radius are simulated by the model p

ISSN:0032-3888    

DOI:10.1002/pen.760250111

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY