摘要:

AbstractAn apparatus is described and a method discussed for determining the rheological characteristics of elastic liquids during extension at constant rates of deformation and extension. The material studied was polyisobutylene of molecular weight 7 × 104. At low constant deformation rates steady‐flow regimes were achieved, with corresponding equilibrium high elastic strains. A detailed study has been made of the process of attainment of steady‐flow regimes and it is shown that before steady flow is reached the curve of longitudinal viscosity versus strain passes through a maximum. As the rate of deformation rises, the strains at which steady–state flow regimes are achieved increase, and the time required to reach these regimes decreases. Qualitatively this occurs in the same way as upon shear. The dependence of equilibrium high‐elastic strains (under steady‐flow regimes) on the rate of deformation has been determined. At steady‐flow regimes the stress depends linearly on the rate of deformation at low values of the stress. Under such conditions Trouton's formula is valid. At constant rates of extension the stress versus time curve passes through a maximum which becomes higher with increasing ext

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080101

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractIt is demonstrated that dicarboxylic acids of uniform lengths, obtained by degrading chain‐folded polyethylene single crystals, can be converted to paraffins via the intermediate diiodide by means of the procedure of Barton et al. Thus we are now in the position of obtaining uniform paraffins of chain lengths longer than hitherto available for the study of the crystallization of oligomeric chains. Measurements of melting points and heats of fusion revealed major differences between the paraffins and the corresponding parent dicarboxylic acids. It follows that such measurements on the unmodified products of the nitric acid degradation cannot be used directly for the assessment of the chain traverse length and the degree of crystallinity. It was found further, that the intermediate diiodide is a sufficiently close approximation to the paraffin for the purposes just quote

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080102

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractA method for the determination of the molecular weight spread in the narrow peaks in the GPC chromatograms of nitric acid‐degraded polyethylene is presented. It is found that polar endgroups added to the polymer chains during scission cause the peaks to be broader than those of paraffins with the same molecular weight spread. After allowing for this extra instrumental broadening, estimates are made of the molecular weight spread for unannealed and annealed single crystals of polyethylene and bulk polyethylene as a function of degradation time. It is proposed that after long degradation times the molecular weight spread is a measure of fluctuations in the original crystalline lamellar thicknes

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080103

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractA simple method of preparing thin uniform films of high polymers has been examined for growing single crystals from solution. Single crystals of polyethylene, polypropylene, polybutene‐1, polyacrylonitrile, and cellulose triacetate have been obtained by this method. Different stages of growth reveal different growth features that are also obtained from solutions of these polymers by changing temperature and concentratio

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080104

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe real and imaginary components of the complex piezoelectric strain constant, which relates the polarization to the applied stress, have been determined for elongated films of poly(γ‐methylL‐glutamate) over the temperature range −170°C to +170°C at a frequency of 20 Hz. The variation of the piezoelectric constant with temperature is similar for both α‐helical and β‐form molecular conformations. The sign of piezoelectric polarization is opposite forLandDpolymers. A simple model, representing the piezoelectric crystallites as embedded in nonpiezoelectric amorphous regions, is proposed to account for the piezoelectric temperature dis

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080105

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe adsorption of several toluene‐soluble polymers at the toluene–water interface has been investigated by using the duNouy ring method of measuring interfacial tension γT/W. Polystyrene and poly(ethylene‐co‐vinyl acetate) (11.1 mole‐% vinyl acetate) have little affinity for this interface at 29°C, but poly(methyl methacrylate) (PMMA) (M̄n= 420,000) and ethyl cellulose (EC) (M̄n= 50,100; 49.1% ethoxyl) adsorb significantly at concentrations as low as 1.0 × 10−4g/100ml. A plot of interfacial tension lowering versus initial logarithm of initial bulk phase polymer concentration is linear from 1.0 × 10−4to 1.0 × 10−1g/100 ml for EC and 1.0 × 10−4to 1.0 × 10−2g/100 ml for PMMA. When the PMMA concentration increases to 1.15 × 10−1g/100 ml, its adsorption behavior changes markedly. Prolonged time effects occur and adsorption becomes dependent upon dissolved water content of the toluene prior to formation of the toluene/water interface. Such effects are not observed with the other solutions studied. Increasing temperatures have variable effects on values of γT/Wfor the polymer solutions studied. Experiments with various polymer mixtures indicate that the polymer loweringT/Wthe most is preferentially adsorbed at the toluene–water interface and rapidly displac

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080106

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe high degree of flexibility of blends containing minor amounts of partly crystalline copolymers of ethylene and vinyl acetate in paraffin wax seems to be a manifestation of some type of interaction. Low‐angle x‐ray diffraction of such blends showed a new long spacing intermediate in length between the polymer long spacing and thecaxis length of the wax unit cell. This new long spacing appears to be a consequence of isomorphism involving cocrystallization of polymeric ethylene sequences and wax molecules. A lesser type of isomorphic interaction, epitaxy, occurs in polyethylene–wax blends: wax overgrows crystals of already crystallized polyethylene in the same orientation without a change in itscaxial dime

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080107

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe theoretical justification for usingM[η], or a similar quantity, as a universal calibration parameter in GPC is reviewed. The equation based on this parameter is applied to transform the primary calibration curve, obtained by means of polystyrene samples, into calibration curves for poly‐α‐methylstyrene, polypropylene, and linear polyethylene. The Mark–Houwink equations for these polymers, as they are used in the transformation, are discussed. The resulting GPC calibration curves are compared with molecular weights and peak elution volumes of fractionated poly‐α‐methylstyrene and polypropylene. The same comparison is made with samples of polypropylene and polyethylene having very broad molecular weight distributions. The agreement lies within experi

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080108

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe melt rheological properties of both linear and branched polyethylene were investigated by use of narrow molecular weight distribution fractions and experimentally polymerized samples. Studies carried out in steady shear and in oscillatory shear yielded information concerning both the melt viscosity and the melt elasticity as a function of molecular structure, where the latter was characterized by various solution property techniques. The 3.4–3.5 power dependence of the low shear limiting viscosity on molecular weight was confirmed for linear polyethylene. The effect of long‐chain branching on rheological properties was defined both at constant molecular weight and at constant molecular weight distribution and coupled with variation of molecular wei

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080109

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe investigation of the effect of molecular structural variables on the melt viscosity of polyethylene was extended to the shear dependent region by application of a reduced variables treatment following, in a formal sense, that of Bueche. Viscosity–shear rate data were obtained for a series of experimentally polymerized linear polyethylene samples having a range of molecular weights and molecular weight distributions as characterized primarily by gel permeation chromatography. These data could be superimposed on a single reduced variables flow curve using parameters which were a function only of temperature, limiting Newtonian viscosity, M̄w, and M̄w/M̄n. The same treatment was successfully applied also to branched (low‐density) fraction data discussed in a previous paper, with additional correction for long‐chain branching. However, different reduced variables curves were obtained for the branched and line

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080110

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY