摘要:

AbstractThe sorption of ammonia by polystyrene was investigated by pulsed nuclear magnetic resonance (NMR) relaxation techniques. The concentration of sorbed gas was determined from the intensity of the gas signal and analyzed by the dual mode sorption model. The relaxation data were used to examine the validity of assuming that the molecules exchange rapidly between sites and that the adsorbed species is relatively immobile. Both assumptions were found to be substantially correct although the possibility that the adsorbed species may have some small mobility (no more than 5% that of the faster moving molecules) could not be eliminated.

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130901

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractMixtures of crosslinkable ethylene–propylene terpolymer with saturated ethylene–propylene copolymer (molecular weights 3.6, 16.7, and 45 × 104) containing up to 50% by weight of copolymer were crosslinked by sulfur, leaving the saturated copolymer unattached and free to reptate in the terpolymer network. Stress relaxation in small simple elongations (stretch ratio about 1.15) and dynamic Young's modulus at frequencies from 3.5 to 110 Hz were measured at temperatures from 10 to 50°C. Comparison with the properties of the terpolymer crosslinked without added copolymer showed contributions to stress relaxation and mechanical loss attributable to the unattached species. The time required in stress relaxation for the portion of the modulus attributable to the unattached species to decay to half its plateau value,t1/2, is approximately proportional to the 3.5 power of the molecular weight;t1/2appears to be slightly smaller for networks containing 50% than for those containing 25% unattached comp

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130902

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractFurther stress relaxation experiments, mostly at 50°C, are reported on mixtures of crosslinkable ethylene–propylene terpolymer with saturated ethylene–propylene copolymer (molecular weights 3.6 and 45 × 104) containing up to 50% by weight of copolymer, crosslinked by sulfur to leave the saturated copolymer unattached and free to reptate in the copolymer network. Stress relaxation was measured in small simple elongations (stretch ratio about 1.15) on samples which had been extracted to remove a large part of the unattached copolymer and dried. The relative increase in modulus at long times (104sec) increased with the proportion extracted; at short times (1 sec), extraction of the lower molecular weight copolymer increased the modulus to about the same extent but extraction of the higher molecular weight copolymer affected it very little. The relaxation modulus of the copolymer extracted from sample 50H (50% copolymer of high molecular weight), obtained by difference, agreed with that for the total copolymer except for a small difference probably attributable to molecular weight selectivity in the extraction. Stress relaxation was measured on sample 50H at six higher elongations up to a stretch ratio of 3. The dependence of stress on time and strain was consistent with an analysis based on the following assumptions: (a) linear additivity of the network and unattached copolymer contributions, (b) strain–time factorization of the stress contributions from the individual components, (c) a strain dependence for the unattached component corresponding to the presence of a Mooney–RivlinC2termonly, (d) a strain dependence for the network component which does not follow the Mooney–Rivlin equation but is dominated by a simple neo

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130903

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractSharp polymer fractions have been obtained in preparative‐scale gel‐permeation chromatography by use of a column set packed with polystyrene gel particles of about 10 μ diameter. When 0.13 g of standard polystyrene NBS 706 was fractionated per injection, fractions with polydispersities of about 1.02–1.03 were obtained over the molecular weight range 104–106. Effects of a injection volume, solution concentration, and fraction volume on fractionation efficiency were also investigated. Polydispersities of fractions increased appreciably with increasing amounts of polymer

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130904

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractChain characteristics of a linear sulfonate‐containing homopolymer, sodium poly(3‐methacryloyloxypropane‐1‐sulfonate), in aqueous salt solutions (ionic strength,Cs= 0.01Nto 5NNaCl) have been investigated by light scattering and intrinsic viscosity. The molecular weight (M̄w)–viscosity relation can be well described by the Mark–Houwink and the Stockmayer–Fixman equations. The coil is highly expanded even in the most concentrated NaCl solution (6N), and no 1:1 electrolyte was found to precipitate this polymer.A linear relation was observed between the viscosity expansion factor, α3η, and (M̄w/Cs)1/2. Examination of the data in terms of theories for excluded volume and hydrodynamic interaction suggests that the coil experiences dominant hydrodynamic interaction, corresponding to a nondraining coil, and the second virial coefficient and coil expansion at highCscan be correlated by the Flory–Krigbaum–Orofino equation. Results for this polymer are compared with those for other polyelectrolytes, and are discussed in terms of chain structure, flexibilit

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130905

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe behavior of narrow molecular weight distribution polymers has been investigated under uniaxial extension at constant deformation rate and at constant stress. It has been established that up to rupture these polymers behave as linear viscoelastic bodies. A detailed investigation of the rupture phenomenon has shown that the rupture of fluid polymers is due to their transition to the rubbery state at critical deformation rates, with the result that they disintegrate like quasi‐cured rubbers. The effect of the temperature and the molecular weight on the critical conditions of rupture has been described in terms of viscoelastic relaxatio

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130906

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe complex dielectric constant was measured under elevated pressure for the α relaxation of vulcanized chlorinated polyethylene. Both temperature and pressure effects on the static dielectric constants, the activation enthalpy, and volume, and the pressure dependence of the glass‐transition temperature were obtained. The dependence of shift factors on temperature was expressed by the Vogel–Fulcher–Tamman–Hesse (VFTH) equation: −logaT=A−B/(T−T0). The parametersA,B, andT0for each pressure applied were calculated by minimizing the standard deviation between logaTand experiments. The values of the parameters in the Williams–Landel–Ferry (WLF) equation: −logaT=C1(T−Tg)/[C2+ (T−Tg)], were also estimated from the resulting values of the VFTH parameters. All these parameters depended on pressure. The activation volume plotted againstT−Tgdecrease

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130907

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractTheP–V–Trelation and the heat capacity of a chlorinated polyethylene vulcanizate were measured. Several tests on the validity of thermodynamic treatments of the α relaxation process and the glass‐transition temperature were performed by using dielectric properties. From a study using excess variables, it was shown that the entropy theories represented by the equations of Goldstein and Adam–Gibbs' were slightly better than the free volume theory represented by Doolittle's equation. However the study provided no distinction between the two entropy theories. Some tests were also performed on the pressure dependence of the glass‐transition temperature,dTg/dP, and onH*V/H*VwhereH*Vis the isochoric activation enthalpy andH*Pis the isobaric activation enthalpy. Here, too, the entropy theories were better than the free volume theory. Goldstein's expression gave values of bothdTg/dPandH*V/H*Pclosest to those from the dielectric experiments. The Adam–Gibbs' equation gave a temperature dependence fordTg/dPandH*V/H*Pmost similar to those from the

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130908

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractA rotational cone‐and‐plate rheometer incorporating a drag‐cup torque transducer and a frictionless, wire suspension has been designed and constructed. The instrument design provides for a controlled atmosphere for the sample, including anhydrous conditions necessary for studies on solutions of polymers in strong acids. The rheometer can be used to determine the shear deformation in response to an applied stress, including creep, recovery, and the shear stress in response to an applied steady shear. Both transient and steady‐state measurements are possible. Illustrative examples of the instrument performance ar

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130909

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY

摘要:

AbstractWhen a mixture of two monodisperse samples of poly‐α‐methylstyrene is thermally degraded, the components behave independently, as a first approximation, as shown by GPC and rate of volatilization data. The ratioMw/Mn, before approaching the ultimate value of 2.0, first goes through a minimum at a much lower v

ISSN:0098-1273    

DOI:10.1002/pol.1975.180130910

出版商:John Wiley&Sons, Inc.    

年代:1975

数据来源: WILEY