摘要:

AbstractAn empirical equation is presented which describes polymer solution viscosity, η, over theentireconcentration range from a knowledge of intrinsic viscosity, [η], Huggins constant, k′, and bulk flow viscosity of polymer, η0. The equation is:\documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{\eta _{sp}}}{{C[\eta]}} = \exp \left\{{\frac{{{\rm k'[}\eta {\rm]C}}}{{1 - bC}}} \right\} $\end{document}where solution viscosity, η, is contained in ηsp. No arbitrary parameters are invoked sincebcan be evaluated at bulk polymer (C = polymer density) where everything else is known. The equation accurately portrays the viscosity of polypropylene oxide (PPG 2025) from infinite dilution to bulk polymer in a very good solvent (benzene) and in a somewhat poorer (∼ θ) solvent (methylcyclohexane). The hydrodynamic consequences of the thermodynamic interactions between polymer and solvent are reflected in the constants. This equation should be applicable to other polymer/solvent systems, and thus be immediately useful to those working with concentrated polymer

ISSN:0032-3888    

DOI:10.1002/pen.760100102

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe problem of heat and solvent transfer from plasticized film is considered. The transport equations are solved by a numerical method. The formulation of the model includes the temperature dependence of diffusivity, the dependence of diffusivity on decreasing solvent concentration, as solvent leaves the film, and the latent heat of vaporization of the solvent. The Flory‐Huggins theory is used as a model for vaporliquid equilibrium. Heat and mass transfer coefficients are taken either as constants (to simulate extrusion with blowing at the film surface) or from analytical solutions to the appropriate boundary layer equations (to simulate extrusion into a stationary medium.) The boundary layer theory takes into account the effect of rapid vaporization on heat and mass transfer coefficients. Several numerical solutions were obtained for cases corresponding to extrusion of polyvinylacetate, plasticized with acetone, extruded into ai

ISSN:0032-3888    

DOI:10.1002/pen.760100103

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractEarlier work reported the superposition of flow curves for plasticized compounds of vinyl chloride homopolymer with corresponding curves for unplasticized resin. Viscosity shift factors for three plasticizer systems plotted against temperature define an apparent fusion temperature for the bulk polymer. A Brabender Plasticorder, used as a temperature‐scanning rheometer, determined fusion temperatures for various plasticized PVC compounds. These data confirm a fusion temperature for bulk polymer near 205°C, and permit calculation of Flory‐Huggins χ parameters over substantial ranges of composition and temperature. The thermodynamic parameter correlates well with viscosity shift factors for compounds with polymer volume fractions below 0.6. The possibility is therefore raised of calculating flow characteristics for plasticized PVC compounds from knowledge of χ only. The temperature and composition dependence of χ, estimated for the system PVC‐diiso‐octyl phthalate, is similar to reported variations in simpler polymer‐diluent systems. Thus, PVC‐plasticizer systems may follow analogous ther

ISSN:0032-3888    

DOI:10.1002/pen.760100104

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe kinetics of the molecular vaporization process of 21 plasticizers were investigated in detail. By both isothermal and nonisothermal kinetic methods, it was evident that 11 were quite pure single compounds, while 10 were clearly mixtures of compounds. For the single component species internal energies for vaporization and rates of volatilization are listed. The internal energies of vaporization are about one‐half or less of values one can estimate from the additive factor method of Small. Thus, solubility parameters based on our experimental values are low by about 30 percent. From this and previous work on linear alkanes, it is concluded that in the molecular vaporization process, the large organic molecules studied evaporate approximately as spheres and hence low values for the energy of vaporization are obtained. Consequently, the difference between our experimental energy and that estimated from solubility parameters is the energy for extending the molecule in a vacuum environmen

ISSN:0032-3888    

DOI:10.1002/pen.760100105

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractFlow at the entrance of a tube or channel is of interest in many polymer processes. Except for mathematical treatments at high Reynolds numbers and in creeping Newtonian flow, one must turn to empirical correlating equations and qualitative observations. These are discussed in two parts, one on pressure drop and the other on flow patterns. The discussion of pressure drop is largely a review, dealing with inertial, viscous, and elastic contributions to the pressure drop in tapered and sharp‐edged entrances; also presented are new data for a viscoelastic polymer solution in tapered cone entrances. In the section on flow patterns, stress birefringent data for a very elastic solution flowing into a channel entrance show an unusual effect: stress discontinuities, not unlike “shock waves,” upstream and downstream of the entrances. This is in contrast to Newtonian and less elastic materials in which the stress patterns change gradually between the developed flow region and the entrance r

ISSN:0032-3888    

DOI:10.1002/pen.760100106

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractA method is described for measuring the rate of water vapor transmission through thick sections of polyethylene used as insulation on electrical conductors of pure sodium metal. The technique could be generally useful for materials which do not react with sodium, and for cylindrical samples which can be filled with molten sodium in a dry box. For samples with uniform dimensions the results are extremely precise because sensitive electrical measurements are used. Specimens of products in final form can be employed to determine the effects of variations in processing.

ISSN:0032-3888    

DOI:10.1002/pen.760100107

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractStudies have been made of the heat and light induced oxidation of ether linked commercial thermoplastics using a variety of analytical methods. Our studies on polyoxymethylene, polyphenylene oxide, and its blends with polystyrene are discussed here. Comparisons of heat and light stability are made with thermoplastics previously reported.Heat aging of polyoxymethylene causes a decrease in elongation and weight as well as volatile product formation and changes in the infrared spectrum indicative of chain scission. Exposure to ultraviolet light accelerates the oxidative reaction. Polyoxymethylene copolymer is more thermally stable but both polymers are rapidly degraded during light aging.Investigation of the heat and light induced oxidation of polyphenylene oxide shows that oxidation, in either case, leads to a crosslinking reaction resulting in embrittlement of the polymer. The process is difficult to retard. However, oxygen uptake results indicate that blends of polyphenylene oxide and polystyrene can be suitably stabilized against thermal oxidation. Preliminary results indicate that oxidation of these blends proceeds by a chain scission mechanism.

ISSN:0032-3888    

DOI:10.1002/pen.760100108

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractIn this paper the results of both the theoretical and experimental stress analyses of composite materials reinforced with ribbons are presented. The reinforcing materials for such composites are characterized as two‐dimensional elements which are isotropic in planes parallel to the faces. The theoretical work is based on the finite element method. Experimentally, the photoelastic technique is employed to determine the stresses around the glass ribbons embedded in an epoxy matrix. The specimens, containing a number of aligned ribbons, were loaded in tension parallel to the ribbon width. The variation of shearing stress at the ribbon‐matrix interface as well as the pertubation effect on both the ribbon normal stress and interfacial shear due to the discontinuity of the neighboring ribbons are discus

ISSN:0032-3888    

DOI:10.1002/pen.760100109

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractAn approximate theoretical treatment is given for small compressions of bonded rubber blocks. The component of the compressive force arising from the bonded condition at the loaded surfaces is obtained from a pressure distribution within the block, given by the solution of the corresponding torsion problem. The bending of blocks is treated in a similar way, the pressure distribution in this case being derived from the corresponding bending stress function. The apparent shear of relatively thick blocks is then treated as a combination of shear and bending displacements. The location of an internal rupture and the deformation at which it occurs are also derived from a critical (negative) value of the pressure developed within the block, at which a small cavity increases indefinitely in size. The corresponding critical deformations are calculated for extension and bending displacements. The shear stresses developed at the bonded surfaces under extension, compression or bending displacements are also evaluated.

ISSN:0032-3888    

DOI:10.1002/pen.760100110

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760100101

出版商:Society of Plastics Engineers, Inc.    

年代:1970

数据来源: WILEY