摘要:

AbstractGraessley's theory of entanglement was applied to several model distributions. The distribution functions chosen were such that the differential weight distributions were triangular with respect to a log molecular weight axis. The molecular weight level, breadth of the molecular weight distribution, skewness, and blending of simple distributions were studied in their effect on the steady‐state flow curve. The governing factor for the shape of the reduced flow curve was shown to beM̄z+1·M̄z/M̄w2. Other general features of the flow curve predicted by Graessley's theory were disc

ISSN:0021-8995    

DOI:10.1002/app.1973.070170601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractAccurate solubility limits of polymers are best expressed by molecular weight fractionation curves. Individual curves may be obtained for each polymer–solvent (–nonsolvent) system. A method for predicting solubility behavior, based on solubility parameter δ and hydrogen bonding index γ, is proposed here. The correlation is of the form\documentclass{article}\pagestyle{empty}\begin{document}$\left[\eta \right] = k\frac{{T^{\left( {cQ} \right)} }}{{\left( {v.f} \right)^{\left( {ab + R} \right)} }}$\end{document}where [η] = intrinsic viscosity of precipitated polymer;T= absolute temperature; (v.f.) = volume fraction of solvent;R= (δs− δn) − 0.3(γs− γn);Q= (γp− γe)2.2/(δp− δe);prefers to polymer;srefers to solvent;nrefers to nonsolvent;erefers to solvent system at theta temperature; anda,b,c, andkare fitted constants. The correlation was derived from data for poly(vinylpyrrolidone) and polyacrylamide. It probably is limited to systems in which the precip

ISSN:0021-8995    

DOI:10.1002/app.1973.070170602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe diffusions of both caprolactam and water from nylon 6 melts have been measured using a semiinfinite geometry. The process involving diffusion and chemical reaction was analyzed utilizing Higbie's penetration model and known kinetic data. The caprolactam and water diffusion coefficients are, respectively, 8 × 10−8and 2.5 × 10−4cm2/sec. Using the data, molecular weight profiles were obtained for both semiinfinite and cylindrical geometries as a function of melt depth and

ISSN:0021-8995    

DOI:10.1002/app.1973.070170603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractExperimental non‐Newtonian viscosity, primary normal stress difference, complex viscosity, and shear stress relaxation were taken for highly fractionated polystyrene in Aroclor 1248 (a chlorinated biphenyl) as well as for blends differing in molecular weight and concentration. The data are described by three parameters: a zero‐shear rate value, the slope of the log–log plots in the high shear rate region, and a time constant defined as the inverse of the shear rate at the intersection of the low and high shear rate asymptotes. For the functions measured, the low shear rate region is characterized by a dependence onMwand the high shear rate region by a dependence onMn. Implications to polymer processing are disc

ISSN:0021-8995    

DOI:10.1002/app.1973.070170604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe bending stress relaxation and subsequent recovery behavior were determined for merino wool, nylon, and Terylene fibers. The effect of four experimental parameters were investigated, viz., the level of bending strain (0.5–4%), the time of stress relaxation before release (1–1000 min), the relative humidity (0–85%), and the temperature (20°–60°C). For small strains the merino and nylon fibers displayed behavior characteristic of linear viscoelastic materials, while Terylene exhibited a degree of nonrecoverable set. It was possible to construct master recovery curves for fibers held bent for different times before release. These curves can be used as a more convenient means of presenting the results. A relationship was found, for each fiber type, between the percentage stress relaxation and the time taken to recover to a given level of set. This relationship appeared to be independent of the experimental conditions employed. Although the fibers were not linear viscoelastic under all conditions, recovery could be roughly predicted from their stress relaxation behavior at the particular test conditions using the Boltzmann superposition

ISSN:0021-8995    

DOI:10.1002/app.1973.070170605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractMelting temperature of a film biaxially stretched in one step in air at 152 or 140°C increases with increase ofvA, whereas heat of fusion and density decrease with increase ofvA, wherevAis the degree of stretching in area. The rapid decrease in density occurs forvA>10. Extrapolation of the plot of the density versusvA−1/2gives a value of 0.870 g/cm3at infinitevA, which has been reported as the amorphous density of isotactic polypropylene by Farrow. This is so because the fine structure of the film becomes more and more amorphous with further stretching and reaches completely amorphous state at infinitevA. The temperature of stretching has a strong effect on the thermal behavior of a film; a low stretching temperature (140°C) brings about lower melting temperature, heat of fusion, and density. Crystallinity after melt press has not so large an effect on the melting behavior as the stretching temperature. Melting temperature and the shape of the thermogram also depend on the heating rate. There is an appropriate heating rate depending onvAwhich gives the minimum melting temperature. With stretched samples, a small side peak or a shoulder appears at a relatively low temperature in the thermogram when a high heating rate is u

ISSN:0021-8995    

DOI:10.1002/app.1973.070170606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractCotton cellulose was separately oxidized by potassium metaperiodate, potassium dichromate–sulfuric acid, and potassium dichromate–oxalic acid at two oxidation levels, and the resulting oxycelluloses were further modified by treatment with chlorous acid and sodium borohydride in order to prepare a series of chemically modified celluloses with different functional groups. These fiber substances were dyed with leuco‐flavanthrone at 40°C for different periods till equilibrium was reached. Adsorption isotherms were obtained with three purified vat dyes, and thermodynamic affinity of the dyes for the modified celluloses was determined, taking into consideration the adsorption of hydroxyl ions by cellulosic material and of sodium ions by carboxylate groups of oxycellulose. The presence of aldehyde and carboxyl groups is shown to decrease the rate of dyeing as well as the affinity of th

ISSN:0021-8995    

DOI:10.1002/app.1973.070170607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractMolar volumes of substantially amorphous polymers may be calculated by using additive constants derived from constitutive atomic and structural parachor contributions. For 34 polymers, ranging in density from 0.83 to 2.03 g/cm3, the greatest error in the calculated molar volume compared with the measured value was 13.9%, while for 30 of the polymers the error was less than ±7%, with a mean error of ±3.9

ISSN:0021-8995    

DOI:10.1002/app.1973.070170608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe amount of residualn‐pentane in expandable polystyrene bead foam (PSBF) has an effect on the strength and dimensional stability of the foam. Data were needed to determine how fast the residualn‐pentane could be removed to enhance the properties of PSBF. An experiment was designed to determine the diffusivity ofn‐pentane through PSBF at various temperatures. Mathematical models based on the appropriate diffusion differential equations were then used to predictn‐pentane concentrations in in cylinders of PSBF. The diffusivity ofn‐pentane through PSBF was found to have a magnitude of 1×10‐8to 1×10−6cm2/sec and to vary with temperature, foam density,n‐pentane concentration, a

ISSN:0021-8995    

DOI:10.1002/app.1973.070170609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe microstructure of cellulose acetate reverse osmosis membranes which have been prepared by the Kesting dry process has been elucidated with the aid of scanning and transmission electron microscopy. Thedry‐ROmembranes consist of three layers: skin, transition layer, and substructure. The gel morphology of each of these layers originates in its sol precursors within the nascent membrane which manage to survive the sol → gel transition intact. The dense skin layer is composed of aggregates of tiny, slightly ellipsoidal nodules which are believed to be paracrystalline in nature. Immediately beneath the skin lies the transition layer, a narrow band of intermediate density consisting of widely separated closed cells. Below the latter lies the porous substructure which is composed of micrometer‐sized, open‐celled voids. Because of the size of their substructural voids, dry‐RO membranes are able to reversibly undergo wet–dry cycling without densification and loss of p

ISSN:0021-8995    

DOI:10.1002/app.1973.070170610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY