摘要:

AbstractThe effects of plasticization on the transport of gases and vapors in and through glassy polymers are examined from the viewpoint of the “dual‐mode” sorption model with partial immobilization. The analysis assumes the existence of two penetrant populations with different mobilities in the Henry's law and Langmuir domains of the glassy polymers. These mobilities are characterized by their mutual diffusion coefficientsDDandDH. The plasticization of the polymer by penetrant gases is reflected in the concentration dependence ofDDandDH. Expressions for the effective (apparent) diffusion and permeability coefficients are derived assuming thatDDandDHare exponential functions of the penetrant concentration in the polymers. The results of this study are compared with a similar analysis which assumed the existence of a single mobile penetrant population. The present analysis provides information on the effects of plasticization on the penetrant transport in the Henry's law and Langmuir domainsseparately. The effects of antiplasticization or clustering of penetrant molecules on the effective diffusion and permeability coefficients are also exa

ISSN:0887-6266    

DOI:10.1002/polb.1989.090270201

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractStyrene/maleic anhydride (SMA) and styrene/acrylonitrile (SAN) copolymers have previously been shown to form miscible blends when the MA and AN contents do not differ too greatly. It is shown here that this is the result of a weak exothermic interaction between the MA and AN units by measuring the heats of mixing for appropriate liquid analogs of the various monomer units. The region of copolymer compositions for miscibility of SMA‐SAN blends is predicted from the Sanchez‐Lacombe mixture theory using net interaction parameters calculated from the analog calorimetry results via a simple binary interaction model for copolymers. Lower critical solution temperature behavior was observed for blends of copolymers having compositions near the edge of the miscibility region. Various glass transition, volumetric, and FTIR results are discussed in terms of the interactions obser

ISSN:0887-6266    

DOI:10.1002/polb.1989.090270202

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe interaction of metal sulfonate ionomers with polymers containing low levels of amines has been investigated in solution. For example, zinc sulfo EPDM and a styrene/vinyl pyridine copolymer form such complexes over broad concentration ranges. The resultant solutions offer enhanced viscosities at dilute polymer concentrations. At high polymer levels solutions based on these complexes are lower in viscosity than the ionomer alone. These interpolymer complexes have been shown to exhibit an improved property/rheology balance in bulk systems. In solution, polymer complexes provide control of hydrocarbon solution viscosity not available with conventional polymers. Reduced viscosity‐concentration studies suggest that these polymer complexes are a result of the amine‐containing polymer interacting with intramolecular‐associated ionomer coils, which at higher concentrations form a pseudone

ISSN:0887-6266    

DOI:10.1002/polb.1989.090270203

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractIn this note, scaling laws for rotational diffusivity of dilute monodisperse rigid‐rod molecules (guest rods) in semidilute amorphous polymer solutions (host molecules) are derived. The coillike matrix molecules are modeled as a collection of flexibly connected rigid subunits. This allows an analogy with the Doi‐Edwards theory for monodisperse rigid rods in semidilute solutions to be used in the analysis. Very strong dependencies are predicted for the rotational diffusivity of the rods on host polymer volume fraction and rod length. In semidilute polymer solutions the coils dramatically hinder the rotational freedom of the rods forr2≫ ψp−1,rbeing the rod aspect ratio and ψpthe polymer volume

ISSN:0887-6266    

DOI:10.1002/polb.1989.090270204

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA rheometer utilizing an eddy‐current torque transducer and an air‐bearing suspension is described. The rheometer is coupled with a computer‐based data acquisition system and permits studies of shear deformation for several strain or stress histories. A sinusoidal stress history is used to determine the shear storage and loss compliancesJ′(ω) andJ″(ω), respectively. Step stress histories are used to determine the shear creep complianceJ(t)and the recoverable complainceR(t)or more complicated linear and nonlinear rheological responses related to these. Deformation at constant strain rate is used to determine the stress growth function or the steady‐state viscosity. The rheometer may be used over the temperature range – 10–180°C, with torque from 1 to 106dyn cm, and is adaptabel to use with a variety of sample geometrical shapes (e.g., cone and plate, parallel plate, etc.). Examples of measurements on on viscoelastic fluids and on gels below their yiel

ISSN:0887-6266    

DOI:10.1002/polb.1989.090270205

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractSimultaneous birefringence and elongational viscosity measurements were carried out on molten commercial grade, low‐density polyethylenes during simple elongational flow at constant strain rate and constant temperature. The birefringence increased with time during constant strain rate elongation. The increase in birefringence was a linear function of elongational stress throughout whole elongation, but the elongational viscosity increased in two stages. The increase in elongational viscosity can be divided into linear viscoelastic and nonlnear viscoelastic regions. The linear region appeared at small strain and the nonlinear region appeared at strain greater than 0.7. The elongational viscosity in the nonlinear region increased much more rapidly than that in the linear region. The Gaussian approximation, which is commonly used in molecular models, could be used for the transient elongational flow. A constant stress‐optical coefficientC= 1.3 × 10−10cm2/dyn was obtained for all the elongational experiments, independent of strain rate (0.002‐0.2s−1). The stress‐optical coefficients were weakly dependent on temperature, as predicted by the theory of rubbe

ISSN:0887-6266    

DOI:10.1002/polb.1989.090270206

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe creep behavior of a series of fully cured epoxy resins with different crosslink densities was determined from the glassy compliance level to the equilibrium complianceJeat temperatures aboveTgand at the glassy level belowTgduring spontaneous densification at four aging temperatures, 4,4‐diamino diphenyl sulfone DDS was used to crosslink the epoxy resins. The shear creep compliance curvesJ(t)obtained with materials at equilibrium densities near and aboveTgwere compared at their respectiveTgs.Tgs from 101 to 205°C were observed for the epoxies which were based on the diglycidyl ether of bisphenol A. Creep rates were found to be the same at short times, and equilibrium compliancesJewere close to the predictions of the kinetic theory of rubberlike elasticity. Time scale shift factors determined during physical aging were reduced toTg. At compliances below 2 × 10−10cm2/dyn, Andrade creep, whereJ(t)is a linear function of the cube root of creep time, was observed. The time to reach an equilibrium volume atTgwas found to be longer for the epoxy resin with lower crosslink densities. The increase of density during curing is illustrated for the epoxy resin with the highest crosslink de

ISSN:0887-6266    

DOI:10.1002/polb.1989.090270207

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractIn thin films of polyethersulfone and polycarbonate it is shown that crazing becomes increasingly likely to occur as the temperature is raised. The transition temperature depends on strain rate and molecular weight. Three regimes of behavior can be identified. In both the low‐temperature (shear deformation) and high‐temperature (crazing) regimes the strain to craze is independent of molecular weight. However, in the intermediate crazing regime chain length is important, indicating the importance of disentanglement over this temperature range. It is thought that at the highest temperatures disentanglement is still occurring, but the rate‐determining step is now general plastic flow into the craze fi

ISSN:0887-6266    

DOI:10.1002/polb.1989.090270208

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe compressive behavior of polydiacetylene (PDA) single‐crystal fiber and the buildup of thermal residual stress in PDA/epoxy model composite systems have been studied by Raman‐mechanical spectroscopy. The compressive failure of the PDA fiber has been directly observed when the macroscopic compressive stress, applied during a bending experiment, exceeds a critical value. Fiber failure in model composites caused by thermal residual stress can also be observed by Raman measurements as well as optical microscopy. In fact, the most clear indication of fiber failure was the observation of kink bands formed. The thermal residual stress buildup which resulted from significant temperature changes in this model composite have also been studied. Contrary to most accepted views, our analysis showed the adhesion between the reinforcement fiber to the epoxy matrix to be str

ISSN:0887-6266    

DOI:10.1002/polb.1989.090270209

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractFourier‐transform infrared measurements on atactic and amorphous isotactic polystyrenes have been made during application of strain. On passing through the yield point, spectra indicate an increase of the amount of higher‐energy conformation. In atactic polystyrene it corresponds to an increase ofgaucheconformations whatever the state may be: pure or plasticized samples, blend with another compatible polymer, or styrene‐acrylonitrile copolymer. In amorphous isotactic polystyrene an increase of higher‐energytransconformation is observed. These results strongly support the theory developed by Robertson to explain plastic deformation of p

ISSN:0887-6266    

DOI:10.1002/polb.1989.090270210

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY