摘要:

AbstractThe polymerization of the phenolformaldehyde matrix material of porous glass fiber composites is of vital importance in the production of the composite; it also has an, essential effect on the strength properties of the composite, which correlate directly with the degree of polymerization. With a certain material combination, the optimal strength properties can be obtained by a suitable thermal treatment, which depends on the kinetics of the polymerization process. In this study we found that the highest strength values of the composite are obtained by making the polymerization (curing) rapid at a very high temperature using resins with a high degree of polymerization and a high dry matter content. As regards the structure of the composite, the factors that affect the polymerization process arc density, resin content, and thickness. The results obtained with this kind of a composite are valid within a density region of 600 to 1500 kg/m3. At lower densities, the polymerization process changes, since thermal convection plays a greater role, and at higher densities the insulating effect of porosity begins to decrease.

ISSN:0032-3888    

DOI:10.1002/pen.760260602

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe melt strength method is analyzed in terms of its ability to predict the axial stress levels found in tubular film extrusion of low density polyethylene. For certain values of the capillary L/D, the level of axial stresses and average Newtonian viscosity found in the filament stretching and film blowing are comparable at the same draw ratio. The elongation to break of the finished film was found to be primarily determined by the axial stress during the film blowing, at constant frost line height.

ISSN:0032-3888    

DOI:10.1002/pen.760260603

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA mathematical model has been developed to simulate the pultrusion process, namely the profiles of temperature and the degree of cure in both the axial and radial directions in a pultrusion die of cylindrical shape. For the study, the equations of continuity and energy transport, coupled with a kinetic expression for the curing reaction, were solved numerically, using a finite difference method. For the kinetic expression, we used an empirical expression of the form dα/dt = (k1+ k2αm)(1 − α)nto describe the curing behavior of both unsaturated polyester and epoxy resins. Differential scanning calorimetry (DSC) was used to investigate the curing behavior of the following systems: unsaturated polyester resin/glass fiber, epoxy resin/glass fiber, and epoxy resin/carbon fiber. The results of DSC runs were used to determine the kinetic parameters, which enabled us to predict the effects on the pultrusion characteristics of the following variables: (1) the type of initiator; (2) the type of fiber reinforcement; (3) the type of resin; and (4) the pulling speed and hence the residence

ISSN:0032-3888    

DOI:10.1002/pen.760260604

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractWater absorption studies were made on a series of high nitrile barrier polymers, as a function of polymer composition, rubber content, temperature, orientation and relative humidity. Results indicate that absorbed water has a great influence on both mechanical and thermal properties of the polymer. Absorbed water in high nitrile polymers causes a large decrease in the glass transition temperature and yield stress. These effects are found to depend on polymer composition, amount of absorbed water, and degree of orientation. The significance of these results is discussed in relation to end‐use properties of the polyme

ISSN:0032-3888    

DOI:10.1002/pen.760260605

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of melt compressibility on a wire‐coating process have been investigated, assuming that the compressible behavior of a polymeric melt obeys the Spencer‐Gilmore equation of state. The compressible model is distinctly different from the incompressible model in two ways: (1) it has substantially lower pressure build‐up within the die, and (2) the location of the maximum velocity is closer to the traveling wire position. As a result, the velocity profile within the die may change from a parabolic shape to a shape somewhat similar to that observed in a drag‐flow case; and the shear stress generated by the fluid on the moving wire is no longer constant. Calculations indicate that the effect of melt compressibility during wire coming may not be neglected if the wire speed Ls greater than 50 cm/s (100 ft/min). In addition, the relationships between processing parameters and product coating thickness for both compressible and incompressible fluids are quite di

ISSN:0032-3888    

DOI:10.1002/pen.760260606

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe spinning drop method is used to measure the interfacial tension of molten polymer systems. It proves to be a simple and rather fast measuring method, while satisfactory agreement with literature values, obtained with the pendant drop method, is achieved.

ISSN:0032-3888    

DOI:10.1002/pen.760260607

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractIn this paper it is shown that the formation and subsequent breakup of threadlike particles are important disperging mechanisms and largely govern the morphology resulting from a polymer blending process. Experiments on the breakup of Newtonian threads surrounded by a second Newtonian fluid have been carried out and good agreement with Tomotika's theory is achieved. Experiments on the breakup of viscoelastic fluid threads showed the influence of shear thinning and stretch thickening effects of the fluids used. To investigate the influence of non‐Newtonian behavior of molten polymers on capillary instabilities, experiments were carried out on the breakup of molten polymer threads embedded in a second polymer melt. Surprisingly an absence of shear thinning and stretch thickening effects was noticed and good agreement with Tomotika's theory was obtained. Finally, the stability of threads of fluids exhibiting a yield stress was studied. A criterion predicting the stability of such threads was established and verified experimentally. On the basis of this criterion a possible explanation is given for the stability of a certain class of co‐continuous morpholog

ISSN:0032-3888    

DOI:10.1002/pen.760260608

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe objective of a chemoviscosity model of a thermosetting resin is to describe the change of viscosity for a temperature‐time program. A model is most advantageously developed by starting with a viscosity‐temperature relationship and then relating the parameters of this equation to the rate of polymerization. Thus, the chemoviscosity is related directly to the polymerization kinetics of the thermosetting resin and, thereby, to its chemical composition. Viscosity‐temperature relationships based on free‐volume theory such as the Williams‐Landel‐Ferry equation and the Vogel equation appear to fit the chemoviscosity of an amine‐cured epoxy resin more precisely than relation ships based on resin flow as an acti

ISSN:0032-3888    

DOI:10.1002/pen.760260609

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractOver the past decade great strides have been made in the measurement, modeling and application of the rheology or viscosity history of curing thermosets. This paper will review the work that lead to the formulation of a simple predictive model to simulate the viscosity path of curing epoxies and to the use of the model in the understanding of the epoxy lamination process. Subsequent work by others that has clearly refined, extended, and simplified the method will be discussed.

ISSN:0032-3888    

DOI:10.1002/pen.760260610

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractViscoelastic properties in terms of complex viscosity |η*| and storage modulusG' have been studied for highly filled polymer composites. The viscous response and elastic response to changes in the frequency of dynamic oscillations have been fitted through an appropriate Theological model. A relationship between |η*| andG' is shown to exist, and the model parameters determined through the correlation have been shown to be useful in estimating the viscoelastic properties of commercially important ferrite‐filled polymeric systems with loading in the range of 87–94 weight‐

ISSN:0032-3888    

DOI:10.1002/pen.760260611

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY