ISSN:0032-3888    

DOI:10.1002/pen.760251102

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760251103

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractSimha's equation of state provides the relation between reduced pressure, temperature, and volume (P̃, T̃, and Ṽ, respectively) and the occupied site fraction,y=y(P̃, T̃). The latter theoretical parameter combines thePandTeffects on the occupied and unoccupied (“free volume”) part of the model liquid. It can be computed for each liquid once the thermodynamic reducing parameters are known. Empirical correlation between published zero shear viscosity data, η = η (P,T), andyindicates that forn‐paraffins and molten polymers η is a single parameter function: η = η (y). The mathematical form of this dependence was explicitly given forn‐paraffins. However, for polymers the correlation depends on molecular weight, molecular weight distribution, branching, composition, etc. In Practical terms, η = η (y) should be determined for each polymer by measuring the temperature dependence of η in as wide a range ofTas possible. Then pressure effect on η can be determined from η = η(y) plot, knowing

ISSN:0032-3888    

DOI:10.1002/pen.760251104

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe exit flow from a capillary is analyzed with the help of macroscopic mechanical energy and momentum balances. The analysis shows that primary normal stress differences cannot be determined from the exit pressures under the assumption that the flow is viscometric down to the exit. This assumption and the second one (made by Han [9]) that both slit and capillary exit pressures are the same would lead to unacceptable results. Published exit pressure data for polyethylene melts are shown to be unreliable because of large hole‐pressure errors in the pressure measurements. Pressure profiles obtained with a thin tube technique for the flow of a poly(isobutylene) solution indicate that the flow does not remain fully developed near the exit. Moreover, it is shown that for this polymer solution the excess viscous dissipation at the exit contributes to approximately 90 percent of the exit pressur

ISSN:0032-3888    

DOI:10.1002/pen.760251105

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 a typical polystyrene melt in the entry and exit regions of a slit die. Instead of using a general viscoelastic constitutive equation, simplified models were used that include correlations based on experimental data available in the literature for the shear and elongational viscosities and the normal stresses. With such simple models convergence of the iterative scheme is extended to relatively high Deborah numbers (De≈ 5). The models predict vortex growth in the entry region and an increase of extrudate swell at the exit in qualitative agreement with experimental observations. It was found that the normal stresses are primarily responsible for these phenomena, while the elongational viscosity tends to increase the end (Bagley) correction and decrease the swell

ISSN:0032-3888    

DOI:10.1002/pen.760251106

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractCommercial high density polyethylene (HDPE), low density polythylene (LDPE), and linear low density polyethylene (LLDPE) resins were tested at 150, 170, and 190°C in steady state, dynamic, and extensional modes. Within the low rates of deformation\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}= ω ≤ 0.3, the steady state and dynamic functions agreed: η = η′ andN1= 2G′; at the higher rates, the steady state parameters were larger. The elongational viscosity, ηe, was measured under a constant rate,\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}, or stress, σ, condition. In the first case for LLDPE, the transient η etreached an equilibrium plateau value, ηe. For HDPE, η etincreased up to the break point. For LDPE, stress hardening was recorded. Under constant stress the ηe, could always be determined; its value, within experimental error, agreed with the maximum value of η etdetermined in a constant\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon$ \end{document}experiment. The maximum strain at break was only ε = 1.5 for HDPE and 3, to 4 for LDPE and LLDPE. The rate of deformation dependence of the η (or η′) and ηnmay be discussed in terms of the Trouton ratio,RT= ηe/3η at\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}= ω =\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon$ \end{document}:RT≤ 1.2 for LLDPE,RT≤ 2.5 for HDPE, andRT≤ 15 for LDPE. The PE resins were extruded at 190°C through a laboratory extruder equipped with a slit or rod die. The rotational speed of the screw varied from 0 to 90 rpm. Extrusion pressure, output, and energy were measured and correlated with th

ISSN:0032-3888    

DOI:10.1002/pen.760251107

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA mathematical model of the dynamics and heat transfer of the film embossing process has been developed. The thermal analysis around the preheat roll is determined from an unsteady, two‐dimensional heat conduction equation along with appropriate boundary conditions by neglecting the curvature of the preheat roll and choosing a Lagrangian reference frame. The heat transfer occurring between the preheat roll and the embossing rolls is based on a one‐dimensional analysis, including both convective and radiative effects. The deformation occurring in the nip region is analyzed for two different situations. For the case where the surface features are small in comparison with the film thickness, a modified one‐dimennsional calendering analysis is given, accounting for the irregular geometry of the embossing roll surface. For the case where the polymer does not make complete contact with the surface of the engraved channel, the local deformation is determined by means of a simple one‐dimensional cavity filling model. The required pressure distribution is determined by means of a simple one‐dimensional cavity filling model, The required pressure distribution is determined by means of a conventional calendering analysis. The analysis for the case of a Newtonian and power‐law model is presented in detail. The model yields qualitatively correct results and is computation

ISSN:0032-3888    

DOI:10.1002/pen.760251108

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractSimple pseudo‐steady state relations between the hydraulic and nozzle pressures of an injection molding machine were presented and verified experimentally. A simulation study was performed to evaluate the performance of simple controllers using dynamic models developed for the hydraulic and nozzle pressures. The controllers chosen were the discrete proportional, proportional‐integral (PI), and proportional‐integral‐derivative (PID) types, tuned according to the ITAE criterion. The control of hydraulic pressure simulation showed that the PI controller had the best overall performance, whereas the result of nozzle pressure control loop simulation showed that the PID controller performance was better than that of the PI controller. All the controllers, in both loops, gave responses that were about an order of magnitude more rapid than the open loop r

ISSN:0032-3888    

DOI:10.1002/pen.760251109

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760251110

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760251101

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY