摘要:

AbstractA detailed model for the prediction of the behavior of batch or continuous emulsion polymerization reactors has been formulated, and an efficient numerical scheme for simulation developed. The model makes use of population balance equations and detailed mechanisms for chemical and physical rate processes. The numerical procedure chosen for its solution is orthogonal collocation on finite elements. In this paper, a few comparisons with experimental data are presented to demonstrate the model validity. Finally, a parametric sensitivity study is carried out to identify the most important kinetic and physical parameters. In the sequel, a comprehensive comparison of model predictions with a wide variety of experimental data will be presented.

ISSN:0032-3888    

DOI:10.1002/pen.760280502

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA detailed model for emulsion polymerization is compared with extensive data from continuous stirred tank reactors. Model predictions are compared with both steady‐state and dynamic data, for polymerization of styrene, methyl methacrylate, and vinyl acetate. Good agreement between model and experiment is achieved with one set of parameters and without any data fitting. The results show that the model is capable of predicting all of the experimentally observed phenomena including steady‐state multiplicity, sustained oscillations, ignition and extinction dynamics, and overshoot during start

ISSN:0032-3888    

DOI:10.1002/pen.760280503

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractIn many operations in polymer processing, such as polymer blending, devolatilization, or incorporation of fillers in a polymeric matrix, continuous mixers are used; e.g., corotating twin‐screw extruders (ZSK), Buss Cokneaders and Farrel Continuous Mixers. Theoretical analysis of these machines tends to emphasize the flow in complex geometries rather than generate results that can be directly used (1–5). In this paper, a simple model is developed for the hot melt closely intermeshing corotating twin‐screw extruder, analogous to the analysis of the single‐screw extruder carried out in 1922 and 1928 (6, 7). With this model, and more specifically with its extension to the complete nonisothermal, non‐Newtonian situation, it is possible to understand the extrusion process and to calculate the energy, specific energy, and temperature rise during the process with respect not only to the viscosity of the melt, but also to the screw geometry (location and number of transport elements, kneading sections and blisters, pitch, positive or negative, screw clearance, and flight width) and screw speed. To support the theoretical analysis, model experiments with a Plexiglas‐walled twin‐screw extruder were performed, in addition to practical experiments with melts on small‐ and large‐scale extruders, with very reasonable results, In Part 2, the Buss Cokneader will be ana

ISSN:0032-3888    

DOI:10.1002/pen.760280504

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe wire‐coating process was analyzed numerically making use of a particular die design employed in highspeed industrial operations. Both the lubrication approximation theory and a fully two‐dimensional finite element analysis were applied under isothermal and nonisothermal conditions, respectively. Particular emphasis has been given to the heat transfer effects between the melt arid the solid and free boundaries. A variety of thermal boundary conditions was studied, ranging from adiabatic to constant temperature walls. The influence of dimension less groups such as Peclet, Nahme, and Biot numbers is examined. Oscillation‐free solutions are obtained for the temperature field by using a standard finite element Streamline‐Upwind/Petrov‐Galerkin technique. Rheological data for a wire‐coating low‐density polyethylene (LDPE) resin (Alathon‐3535) were used in the analysis. The predictions include pressure and temperature distributions, shear stresses and shear rates both at the die wall and the wire, and wire tension for different wire speeds. The numerical results are compared with a set of experimental data for LDPE in a typical die used by Du Pont Co. It is found that the isothermal lubrication approximation for power‐law fluids overestimates pressure distributions when applied at die operating temperature. The nonisothermal finite element analysis gives better predictions, especially when realistic thermal boundary conditions are imposed, with the experimental results lying between those found from simulations assuming isothermal walls (upper limit) and adiabatic wa

ISSN:0032-3888    

DOI:10.1002/pen.760280505

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper defines through a mathematical model the advantages and disadvantages of barrier screws as far as their melting and mixing performances in the transition zone are concerned. The melting analysis is based on the Tadmor's original model, and the flow in the melt channel is considered to be non‐Newtonian and nonisothermal. The performance of these barrier screws is investigated for the solids channel in terms of melting rate/interface a I contact area; melting efficiency; melting length; solid bed velocity profile; and power consumption in the melt film at barrel surface. For the melt channel, their performance is investigated in terms of pressure buildup; average bulk temperature; power consumption in the melt channel and in the main flight clearance at barrel surface; and average bulk mixing. The present study confirms that the increased‐pitch multichannel screw (Ingen Housz screw) outperforms clearly the other barrier screws investigated, since it gives the highest melting rate with reasonable pressure buildup in the melt channel. When compared with conventional screws, all the barrier screws examined give better melting performa

ISSN:0032-3888    

DOI:10.1002/pen.760280506

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA mathematical model is developed for simulating the pultrusion process of unsaturated polyester resin, using a mechanistic kinetic model based on free radical polymerization. In their previous publications (Refs. 1and7), Han and Lee used the mechanistic model to simulate the curing behavior of unsaturated polyester resins under isothermal conditions, employing the differential scanning calorimetry data obtained for a range of single initiators and multiple initiator systems. For the sake of mathematical convenience, a pultrusion die of cylindrical geometry was considered. The mathematical model developed permits one to choose any number of initiators when predicting the distributions of the degree of cure and temperature in both the radial and axial directions of the die. The effects of material variables (e.g., the type and concentration of mixed initiators) and processing conditions (e.g., pulling speed and die temperature distribution) on the performance of the pultrusion are evaluated.

ISSN:0032-3888    

DOI:10.1002/pen.760280507

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractInjection molding can be used to fabricate fiber‐reinforced polymer composites by impregnating a continuous fabric mat preplaced in a mold cavity with a polymer resin. The mold‐filling time is dependent on the flow and heat transfer behavior in the mold. A model is proposed that considers the non‐Newtonian How through the porous fabric mat and the heat transfer between mold, fabric mat, and flowing fluid. The model was simulated for the mold filling of a carbon fiber mat with a pseudoplastic polymer solution. The results from the simulation provide Information for optimizing mold‐filling parameters through proper selection of inlet fluid pressure, heat source temperature, and type of polymer‐solve

ISSN:0032-3888    

DOI:10.1002/pen.760280508

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760280501

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY