摘要:

AbstractThe present research program, based upon the experimental performance of a 20 mm counter‐rotating, non‐intermeshing twin screw devolatilizer with several polymer/solvent systems has developed theoretical approaches to modeling both the bubble growth dominated mass transfer regime as well as the essentially bubble free regime (1, 2). This work encompasses the area of transition from the bubbling to the non‐bubbling areas. This transition to some degree, probably exists in nearly all real devolatilization processes. The work combines a foam simulation model, which integrates elementary bubble processes, with the mass transfer from single phase liquid films through a penetration theory based model. The modeling is successful at correlating the experimental data and shows realistic effects with regard to residence time, surface area, and average mass transfer coefficient as functions of vent lo

ISSN:0032-3888    

DOI:10.1002/pen.760301102

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractRolltrusion, a single step solid state deformation process, has been successfully applied to isotactic poly(propylene), iPP, to produce unique 3‐D properties. Mechanical property enhancement not only occurs in the principal draw direction, but also in the transverse directions. A systematic series of standard (ASTM) tensile and compressive experiments were made on well oriented materials supporting this claim. Tensile testing was also performed on dumb‐bell shaped specimens cut at various angles to the main deformation direction. A variety of observations were made during testing. Deformation bands, anisotropic yielding, and ductile‐to‐brittle behavior were observed. These results are presented along with a morphological model that has been developed to account for the behavior of these unique triaxially oriented p

ISSN:0032-3888    

DOI:10.1002/pen.760301103

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe influence of polymer molecular weight, molecular weight distribution, and polymer‐solvent interactions on the thickness and topography of spin‐coated polymer films was examined. For films prepared from dilute solutions, highly volatile solvents or fair or “poor” solvents for the polymer adversely affect film surfaces causing nonuniformities (waves) to appear. However, if the concentration of these solutions is increased to approximately the concentration at which entanglements are formed, nearly uniform films are produced even if the solvent employed is highly volatile, such as dichloromethane. When toluene is employed as the solvent, which has a relatively low volatility and therefore forms nearly flat film surfaces, films prepared from dilute solution were found to have thicknesses,h, proportional to η o0.34Ω−0.49for polystyrene and η o−0.39Ω−0.49for poly(methylmethacrylate) where ηois the zero‐shear rate solution viscosity and Ω is the rotational speed at which the films were prepared. These results suggest that the exponents associated with ηoand Ω may be nearly independent of the type of polymer used as long as flat films are produced. Finally, the molecular weight parameter most important in controlling final film thickness for films made from dilute solutions isMv, the viscosi

ISSN:0032-3888    

DOI:10.1002/pen.760301104

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractAn experimental and theoretical study of reaction injection molding (RIM) of polyurea was conducted in this work. A lab‐scale RIM machine was used to carry out the polyurea bulk polymerizations. A “free‐table” viscometer was designed to measure the fast rheological changes and liquid‐solid transition. A mathematical model was proposed to simulate the fast reaction and rheological changes in the polyurea RIM process. The parameters of this model were determined based on the solution polymerization data from FTIR and Haake rheometer measurements. Combined with an appropriate heat transfer equation, this model predicts fairly well the adiabatic temperature and viscosity rises of bulk polyurea reactio

ISSN:0032-3888    

DOI:10.1002/pen.760301105

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe performance of plasticating single‐screw extruders is analyzed by combining three functional sections: (a) solids‐conveying section, (b) melting section, and (c) melt‐conveying section. In the analysis of the melting section, we have incorporated a new concept of solid‐bed deformation (i.e., the rheology of the solid bed) into Lindt‐Elbirli's analysis and included convective heat transfer in the energy equation. Specifically, we have computed stresses on the surfaces of the solid bed, which is surrounded by thin melt films and a melt pool, and, also, computed the apparent modulus of the solid bed in the bulk state as a function of temperature and position within the solid bed, along the extruder axis. From this information, we were able to compute the extent of solid‐bed deformation, by assuming a linear stress‐strain relationship as the constitutive equation of the solid bed. In this approach, we do not assume a priori whether the solid bed is rigid or freely deformable. The solution of the system equations gives us the following information: (a) whether or not the solid bed deforms and if it does, then, how much; (b) the solid‐bed velocity along the extruder axis; (c) pressure profiles along the extruder axis; (d) solid‐bed profiles in the melting zone along the extruder axis; (e) temperature profiles along the extruder axis; (f) velocity and temperature distributions in the melt pool along the extruder axis; and (g) thicknesses of thin melt films surrounding the solid bed. Theoretically predicted solid bed and pressure profiles along the extruder axis are compared with experimental results reported in the literature. We have pointed out an urgent need for measurements of the apparent modulus of the solid bed in the bulk state as a function of temperature and pressure, under a combined shea

ISSN:0032-3888    

DOI:10.1002/pen.760301106

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractFiber glass reinforced polyester parts compression molded from sheet molding compound (SMC) are prone to such surface inconsistencies as porosity and sinks. Even though it appears that some of these defects could be eliminated by techniques such as vacuum molding, the resulting surface, with current technology, is not yet consistently up to automotive standards for exterior body panels. In‐mold coating (IMC) of SMC, is designed to fill porosity, reduce sinks, and furnish a primer‐like coating, thus upgrading the part surface to automotive standards. As a consequence, IMC is generally an integral part of the molding cycle when producing compression molded SMC exterior automotive body panels. Most commonly, in‐mold coating is injected after opening the press slightly so as to separate the mold cavity and the exterior surface of the part to make room for the coating. A second approach is to let the hydraulic pressure of the injected IMC open the mold. Here, we present a mathematical model of the process and show application in predicting injection pressures, fill times, and filling patterns. A comparison with experimental results is also presented. Cycle times required for IMC injection methods is also disc

ISSN:0032-3888    

DOI:10.1002/pen.760301107

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA free radical copolymerization model is proposed for simulating the reaction rates and conversions of styrene monomer and unsaturated polyester resins during curing. This model is based on film theory in which the rate constants reflect both reaction and diffusion resistances. Differential scanning calorimetry in combination with Fourier transform infrared spectroscopy is used to measure the overall and individual reactivities of reacting species. Model parameters are determined from experimental data. The applicability of this model is demonstrated in a cure simulation.

ISSN:0032-3888    

DOI:10.1002/pen.760301108

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe development of composites consisting of wood fibers and recycled plastics offers not only an opportunity to utilize an abundant natural resource but also a means to alleviate the serious plastics disposal problem. In this work, aspen fibers are incorporated into recycled high density polyethylene with a co‐rotating inter‐meshing twin‐screw extruder to study processing‐property relationships. Tensile, impact, and flexural strengths are measured as functions of fiber concentration. The effects of fiber pretreatment, screw configuration, and compounding temperature on the properties of composites are di

ISSN:0032-3888    

DOI:10.1002/pen.760301109

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760301101

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY