摘要:

AbstractWe have developed a new method to measure the true temperature of the polymer melt and its three‐dimensional distribution of a shot stored in the reservoir during injection. By means of this method, it is demonstrated that the temperature distribution of the polymer melt stored in the reservoir is strongly dependent on the setup molding conditions, the polymer investigated, and the geometry of the screw used. Further, it is noted qualitatively that there are two major effects of screw geometry on the temperature distribution of polymer melts. One, which governs strongly the temperature in the high temperature zone, is shear heat generated within the polymer itself in the metering zone of the screw during the transporting process. The second is the ability to preheat and plasticate the polymer in the compression zone, which is indispensable for uniform plasticatio

ISSN:0032-3888    

DOI:10.1002/pen.760300702

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe concentrated solution and melt rheology of poly(vinylidene fluoride) [PVDF] were studied by using a falling needle solution viscometer, a Brookfield viscometer, and a Kayeness capillary rheometer. It was found that the concentrated solution (15 wt% in N‐dimethyl acetamide) rheology exhibited a different behavior for various grades of PVDF produced by different types of polymerization. While Newtonian behavior was found in one type of PVDF, shear thinning was found in another type. The power law model was used to describe the general solution behavior of these materials. Zero shear rate viscosity correlated well with the molecular weight (Mw) of the material. Melt viscosity of PVDF exhibited continuous shear thinning behavior throughout the whole range of shear rates. The data were best fitted by a second‐degree polynomial curve. Correlations were established between the molecular weight, molecular weight distribution, and the parameters of the polynomial curve. These correlations are useful for the prediction of various grades of PVDF designated for specific engineering applications. The correlations obtained from solution provided better and more accurate correlations toMwparameters than those of melt rheol

ISSN:0032-3888    

DOI:10.1002/pen.760300703

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractIsothermal and nonisothermal flows of polymer melts in a screw channel are discussed. An exact solution for the isothermal flow of a power law fluid in a rectangular channel including both longitudinal and transverse velocity components is presented. A method to describe the effects of flights and curvature on flow behavior is proposed. The results are extended to deal with various nonisothermal flow conditions. The proposed theory has been numerically verified.

ISSN:0032-3888    

DOI:10.1002/pen.760300704

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA numerical method has been developed that takes the streamline finite difference method for modeling fully developed multilayer polymer flows and adds to it a simple means of accounting for nonisothermal conditions. In industrial practice, temperature control is often used to match material viscosities and, thereby, to avoid flow instabilities. By numerically calculating both viscosity ratios and normal stress difference ratios, the numerical method allows one to judge the relative stability of different flows and to choose an intelligent set of experiments when designing a coextrusion process. The algorithm has been successfully tested for a number of polymer melt constitutive equations in flows where the viscosity jumps no more than two orders of magnitude between fluids. Results for a rheologically well characterized polystyrene low‐density polyethylene system and for an industrially interesting high‐density polyethylene/Ultem system show that the common practice of matching zero‐shear viscosities is overly simplistic when interface shear rate, conduction, normal stress, and flow rate effects are taken into ac

ISSN:0032-3888    

DOI:10.1002/pen.760300705

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper describes the use of the General Purpose Simulation System (GPSS) to simulate the manufacture of a typical line of thermotropic liquid crystal polymer resins. Specifically considered were composite polymers based on parahydroxybenzoic acid with glass, graphite, or talc added as a filler or reinforcing agent. The process examined consists of a combination of batch and semicontinuous operations. Product campaigning and equipment cleaning requirements were also incorporated into the GPSS model. Different equipment configurations and manpower distributions were simulated to aid in the design of such a polymer plant. The simulation results were analyzed, and the calculated return on investment was used to select the final plant design.

ISSN:0032-3888    

DOI:10.1002/pen.760300706

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA theoretical analysis of the diffusion‐controlled, essentially bubble‐free, mass transfer regime of polymer solution devolatilization has been performed for a counterrotating, nonintermeshing twin‐screw extruder (1). The commonly used penetration diffusion approach is applied specifically to this geometry. Mass transfer from the recirculating pool and barrel film in the closed channel and the pool only in the open channel is taken into account. Use is made in this study of the recently determined pumping characteristics of this geometry (2), which allow the estimation of the length of the extraction section. Mass transfer rate measurements have been taken on a 20‐mm extruder using the model system polystyrene/ethylbenzene. The agreement between the mass transfer calculations and the experimental results is ve

ISSN:0032-3888    

DOI:10.1002/pen.760300707

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractIsothermal aging after a quench from above the glass‐transition temperature (Tg) to below it was studied as a function of cross‐link density for model epoxy networks using small deformation stress relaxation experiments. We found that time‐aging time and time‐cross‐link density superposition principles described the changes observed in the Viscoelastic behavior of the epoxy networks. The aging response in the nonlinear Viscoelastic regime was also studied using creep experiments for one of the networks. It was found that upon aging near to the conventional glass‐transition temperature, the time required for the glass to age into structural equilibrium was independent of the magnitude of the applied stress. This result suggests that large stresses do not erase physical aging (or cause rejuvenation of t

ISSN:0032-3888    

DOI:10.1002/pen.760300708

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760300701

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY