摘要:

AbstractIt has been shown in this investigation that the permeation of propane and propylene through polyethylene membranes exhibit a generalized behavior in the vicinity of the condensation point of the penetrant. Correlations to evaluate the permeation flux are presented.

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100101

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe method of free torsional vibrations was used to determine the temperature dependence of the storage and loss shear modulus of poly(2‐hydroxyethyl methacrylate) samples swollen with ethylene glycol, formamide,n‐propanol, and water. The measurements included the glassy region (starting with temperatures from −130 to −190°C) and the main (α) transition from the glassy to the rubberlike state. At a volume fraction of the low molecular weight compoundvd>0.2, the above systems exhibit, besides the α dispersion, only the secondary (βSW) dispersion, which is generally attributed to the relaxation motions of the hydroxyethyl groups of the side chains interacting with molecules of the diluent. If no separation of the diluent in a second phase occurs at the measurement temperatures, the temperatures of both dispersions decrease with increasingvdand approach the glass transition temperature of the low molecular weight compound. The concentration dependences of the dispersion temperatures were described by an equation derived elsewhere for the concentration dependence of the glass transition temperature. The results indicate that molecules of the diluent contribute significantly to the intensity of the βSWtransition and simultaneously affect its limiting temperatures (forvd= 1 andvd= 0). Specific differences among the systems described above appear only at those temperatures where same of the low molecular weight compound separates into a crystalline or

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100102

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractStatistical radii of gyration, second virial coefficients, and intrinsic viscosities of sharp fractions (M̄w/M̄n≈ 1.1) of polyisobutylene (PIB) covering a wide range of molecular weight (1.6 × 105to 4.7 × 106) were determined in isoamyl isovalerate (IAIV) at a number of temperatures ranging from 20 to 60°C, inn‐heptane at 25°C, and in cyclohexane at 25°C by light‐scattering and viscosity measurements. It was found that IAIV at 22.1°C is a theta solvent for PIB. Analysis of the data by the methods described in preceding papers of this series indicated that, except for minor differences, the conclusions derived from similar studies with polychloroprene, polystyrene, and poly‐p‐methylstyrene hold equally for solutions of the typical linear polymer investigated here. In particular, no decisive evidence for the drainage

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100103

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractNatural rubber crosslinked by dicumyl peroxide in amounts up to 25 parts per hundred of rubber (phr) showed a maximum in tensile strength near 1 phr, followed by a steep decrease to a minimum near 5 phr. The ultimate elongation decreased from 870% at 0.5 phr. to about 10% above 10 phr. The modulus increased linearly with increase of crosslinking. The creep rate decreased from 5.6% per decade at 0.5 phr to zero at 5 phr and higher values. Crystallization, with a resultant abrupt increase in creep, was noted in specimens held in the stretched condition for more than one day. Between 5 and 25 phr this system (when crystallization is avoided) appears to function as an ideal elastic network and can be recommended for studies of rubber elasticity since no variation of modulus with time is observed.

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100104

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractPhotoelastic investigations have been carried out on a number of polymers in the crosslinked rubbery state. These includecis‐polyisoprene, two polybutadienes of different structural configurations, an ethylene‐propylene terpolymer, and a range of styrene—butadiene copolymers. From the measured values of stress‐optical coefficients, together with calculated values of the optical anisotropies of the monomer units in the chain (based on Denbigh's values of bond polarizabilities), estimates are made of the number of monomer units in the equivalent random link (of the Kuhn‐Grün theory) for the polymeric chains considered. Further, from a study of the temperature dependence of the stress‐optical coefficient, the temperature dependence of the lenght of the equivalent random link, and hence of the statistical length of the chain, is derived. The interpretation of the temperature dependence data is discussed in a semiquantitative manner in terms of internal energy differences between different rotat

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100105

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe modified Birnboim transducer and a computerized data acquisition and processing system (DAPS) for the measurement of viscoelastic properties of macromolecular solutions are described. The apparatus has a continuous frequency range from 0.01 to ca. 700 Hz and a viscosity range from 2 to ca. 30,000 poise (sample volume 1 to 1.5 cm2). Sample temperature is controlled to within 0.002°C from −30°C to +80°C. Working displacements are 102to 104Å. The DAPS is designed for precise determinations of the magnitudes and relative phasing of two sinusoidally time‐varying electrical signals (0.02%, 0.02°, respectively, for signals>2 V peak) from 10−2to 105Hz. Cross‐correlation techniques are used for noise rejection. For frequencies below 30 Hz values of the storage (G') and loss (G″) components of the complex shear modulus (G*) of 1 dyne/cm2are determined to within 10% and 4%, respectively, for liquids of moderately low viscosity. Proportionately higher measurement accuracies for typical values ofG' andG″ and the wide frequency and viscosity ranges permit extrapolation to infinite dilution and studies of limited molecular flexibility for many polymer

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100106

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe rate of dissociation of a nonionic detergent, octylphenyl polyoxyethylene ether, was studied by a temperature‐jump technique. A relaxation process which is concentration‐dependent was observed. A linear relation between the reciprocal relaxation time and the detergent concentration above the critical micelle concentration was obtained, from which the rate constant of dissociationkn,n–1of one molecule of detergent from the micelle has been determined. Values ofkn,n–1equal to 0.4 ± 0.05 and 73 ± 5 sec−1at 24.8°C were obtained for detergents with 16 and 30 ethylene oxide units per molecule of surfactant, respectively, showing and increase of the rate constant of dissociation with the length of the hydrophili

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100107

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractDomain structures of solvent‐cast films of A–B–A block copolymers of styrene‐isoprene‐styrene were studied by electron microscopy by use of the OsO4fixation technique. The effects of varying proportions of the two components and the casting solvent upon the domain structures were examined. It is concluded that the domain formation mechanism can be discussed like that of A–B block copolymers irrespective of sequence arrangements, as Matsuo et al. suggested, by treating A–B–A or B–A–B block copolymers as A–(1/2)B or B–(1/2)A block copolymers. The five types of fundamental domain structures—spherical domains of component A in a matrix of component B, rodlike domains of A in a matrix of B, alternating lamellae of the two components, rodlike domains of B in a matrix of A, and spherical domains of B in a matrix of A—are achieved mainly by the change of the fractional composition of the two components for a given solvent. One of the most significant features of the A–B–A block copolymers in contrast to the A–B block copolymers, i.e., that A–B–A chains can interconnect two A domains, was explored by investigating (1) the swelling behavior in a solvent that is a good one for isoprene but a nonsolvent for styrene and (2) mechanical behavior above the glass transitio

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100108

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe following quantities were measured on a number of ethylene–vinyl acetate (EVA) and ethylene–acrylic acid (EAA) copolymers: (1) the small‐angle x‐ray scattering invariant, (2) the overall density, and (3) the crystallinity. Assuming a two‐phase structure, the separate values of the densities of the crystalline and amorphous regions can be calculated from these data. Of these, the crystalline density is compared with the value obtained from the lattice constants. A systematic difference is observed which is ascribed to the presence of comonomeric side groups in the crystalline regions. For the EVA and EAA samples, their concentration is at least 0.3 and 0.5 times the overall concentration, respectively. The amorphous densities are found to be higher than the values calculated from completely amorphous copolymers by extrapolation p

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100109

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractData on tensile strength and elongation at break for a series of Viton A‐HV vulcanizates are discussed. The data were obtained at various extension rates at temperatures from −5 to 230°C (25 ≲T—Tg≲ 260°C) on seven vulcanizates having crosslink densitiesve(estimated from C1in the Mooney‐Rivlin equation) from 0.46 × 10−5to 24.4 × 10−5mole/cm3. At an extension rate of 1 min−1, an increase inveaffects the tensile strength σb(based on the undeformed cross‐sectional area) and the true tensile strength σbσb(based on the cross‐sectional area of a deformed specimen) as follows: σbis essentially constant at a low temperature; it passes through a decided maximum at intermediate temperatures; and it increases to a plateau at elevated temperatures. In contrast, λbσbdecreases markedly at all temperatures, an exception being the most lightly crosslinked vulcanizate(s). Application of time—temperature superposition to the ultimate‐property data gave logaT; its temperature dependence is that typical of nonpolar rubbery polymers. Data on the vulcanizates were compared in corresponding temperature states by plotting log 273σb/T, log 273λbσb/T, and (λb— 1)/(λb— 1)maxagainst logtb/(tb)max, wheretbis the temperature‐reduced time to break and (tb)maxis the value at which the ultimate extension ratio λbattains its maximum, (λb)max. Except for the most lightly crosslink vulcanizate, the comparison shows that 273λbσb/Tand (λb— 1)/(λb— 1)maxare substantially independent of (or only weakly dependent on) crosslink density, that 273λb/Tincreases withve, and that

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100110

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY