摘要:

AbstractDensities of thermally annealed copolymers were measured at 75° and 100°C at pressures to 1 kilobar. The compositions ranged from pure polybutadiene to pure polystyrene, from completely random to completely block copolymers. The experimental results are well represented by the Tait equation. To a first approximation, specific volumes and compressibilities are linear functions of weight per cent styrene. For a fixed composition, the effect of structure on volumetric properties is small. However, it appears that, when compared at the same overall composition, the specific volume and compressibility are larger for the random copolymer; specific volume and compressibility decline slightly when the styrene is in block rather than random for

ISSN:0021-8995    

DOI:10.1002/app.1977.070211101

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe preparation of spherical lignin gel beads, based on the crosslinking reaction between epichlorohydrin and kraft lignin (Indulin AT), is described. The lignin gels prepared were found to be an efficient resin in gel permeation chromatography. The separation of polystyrenes in dimethylformamide is described. The resin was found to separate polystyrenes with molecular weights up to 110,000. An inverse linear relationship between logMand elution volume or the partitioning coefficient was established.

ISSN:0021-8995    

DOI:10.1002/app.1977.070211102

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe effect of concentration on scission of poly(vinylpyrrolidone) (pv= 6,700) in aqueous solution by high‐speed stirring at a speed of 30,000 rpm at 30°C was investigated. Concentration was varied from 0.04 to 2% g/ml. Polymer chains were ruptured to lower molecular weights with decreasing concentration. The rate constant of scission,k, and the limiting degree of polymerization,Pl, in Ovenall's equation calculated for the results were considerably changed in the polymer concentration range from 0.2 to 1% g/ml. The effect of addition of methyl orange on polymer scission was then studied, because the dye had been reported to increase the viscosity of aqueous poly(vinylpyrrolidone) solution because of unfolding of the macromolecule chains. However, no significant effect was found in the concentration range from 0.034 to 0.34 in the molar ratio of methyl orange to poly(vinylpyrrolidon

ISSN:0021-8995    

DOI:10.1002/app.1977.070211103

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

年代:1977

数据来源: WILEY

摘要:

AbstractAn improved differential thermal analytical technique which permits the rapid, convenient characterization of the thermal behavior of crystalline polymers free of any influence of prior thermal history is presented. Characterization of both crystallization and fusion phenomena is described for ethylene/propylene copolymers subjected to well‐controlled thermal scanning techniques. Parameters describing these phenomena are derived. While they are nonequilibrium parameters, they are reproducible and capable of correlation with polymer composition. the crystallization onset temperature determined by this cooling technique was found to relate to the molar ethylene content of the copolymers by an equation similar to the one derived by Flory5based on equilibrium melting point. The relationship was found to hold true for a number of ethylene copolymers, including samples of linear and branched polyethylene, commercial EPDM, and ethylene/vinyl acetate copolymer

ISSN:0021-8995    

DOI:10.1002/app.1977.070211104

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe CO2solubility, permeability, and diffusion time lag in poly(ethylene terephthalate) are reported at 35° and 65°C for CO2pressures ranging from 0.07 to 20 atm. The subatmospheric time lag and permeability measurements were made with a glass system at North Carolina State University, while the measurements between 1 and 20 atmospheres, using an identical polymer sample, were made at The University of Texas with a metal system capable of tolerating gauge pressures up to 30 atm. The measured solubility, permeability, and time lag all show strong deviations from the well‐known simple expressions for gases in rubbery polymers. The solubility isotherm is non‐linear in pressure, and both θ andPare quite pressure dependent, with each showing tendencies to approach low and high pressure asymptotic limits. These effects decrease as temperature increases and would be expected to disappear at or near the glass transition where the amorphous regions become rubbery. The importance of reporting the pressure levels used in transport measurements is emphasized for gas/glassy polymer systems where transport process do not follow linea

ISSN:0021-8995    

DOI:10.1002/app.1977.070211105

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe thermal characterization of a series of polyquinazolones, poly(quinazolone diones), and polybenzoxazinones by thermal analytical techniques (TG, DSC) is described. Comparative thermal stability measurements by dynamic and isothermal TG in air and N2are critically discussed. Kinetic studies by isothermal TG in air and nitrogen leading to activation energies are described. The inherent difficulties in comparative thermal stability studies on complex polymer systems are discussed in terms of their structural and compositional variables and their effect on the assessment parameters used.

ISSN:0021-8995    

DOI:10.1002/app.1977.070211106

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

年代:1977

数据来源: WILEY

摘要:

AbstractRadiolysis of poly(vinyl alcohol) fibers (PVA) in the presence of chloroform and carbon tetrachloride was investigated. Decrease in intrinsic viscosity was observed at lower dosages (up to 2.3 megarads); and above this, an increase was noted. The blank samples irradiated under similar conditions showed a continuous decrease in intrinsic viscosity. A discoloration in the samples irradiated in the presence of CCl4and CHCl3was also observed. It is attributed to double bond formation in the backbone. A marginal decrease in the tensile strength of the irradiated fibers was observed. However, the surface characteristics of the fibers did not change on irradiation. The thermogravimetric analysis revealed a better heat resistance in irradiated fibers.

ISSN:0021-8995    

DOI:10.1002/app.1977.070211107

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

年代:1977

数据来源: WILEY

摘要:

AbstractTriethoxyvinylsilane–styrene and triethoxyvinylsilane–methyl methacrylate binary monomers were polymerized by chemical initiation or by γ‐ray irradiation in the presence of silica gel, fire brick, quartz wool, and glass beads. The amount and composition of the polymers grafted to silicates were analyzed by using pyrolysis gas chromatography. When triethoxyvinylsilane alone was subjected to the reaction with silicates, condensation occurred irrespective of the initiating means, and the extent of the reaction was almost proportional to the specific surface area of the silicate. When binary monomer mixture was applied, incorporation of styrene or methyl methacrylate into the grafted polymer was observed whenever a monomer mixture of high styrene or methyl methacrylate content was submitted to the reaction. On each silicate, the relationship between the composition of polymer grafted on it and that of monomer showed a similar pattern in spite of the great difference of the specific surface area. Almost no participation of styrene or methyl methacrylate was observed when the silicate preirradiated in air or under vacuum was heated with the binary monomer mixture. It was concluded that triethoxyvinylsilane reacts with silicates by condensation and that some of the pendent vinyl groups on the silicates are incorporated into the copolymer with styrene or methyl methac

ISSN:0021-8995    

DOI:10.1002/app.1977.070211108

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

年代:1977

数据来源: WILEY

摘要:

AbstractStress relaxation and creep tests following strain ramps were made on Mylar, both above and below the yield stress. The ramp velocity was varied over a 40‐fold range. All data exhibit nonlinear viscoelastic behavior. However, those obtained above the yield point, i.e., in the plastic region, could be reduced to single master curves for both the creep and the relaxation tests by means of a simple time shift factor. This factor is inversely proportional to the strain rate existing just prior to the tes

ISSN:0021-8995    

DOI:10.1002/app.1977.070211109

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

年代:1977

数据来源: WILEY

摘要:

AbstractA new technique enabling the use of cellulosic material in the fiber form during deuteration‐infrared studies is reported. A minipress, modified to suit the new technique, is described. Since the material was studied in the fiber form, danger of fiber modification during film formation was avoided. Although the usual KBr pellet technique was utilized for scanning the spectra of the deuterated fibers, preparation of pellet as well as scanning were carried out under fully dry conditions, thus completely avoiding the rehydrogenation of deuterated fibers. The modified minipress containing the pellet forms an airtight assembly allowing repeat scans after any length of time without affecting the quality of the spectra of the deuterated sampl

ISSN:0021-8995    

DOI:10.1002/app.1977.070211110

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

年代:1977

数据来源: WILEY