摘要:

AbstractLack of thermorheological simplicity and possible effects of the molecular weight distribution in the softening dispersion of linear amorphous polymers are demonstrated with viscoelastic data on polymethylacrylate PMA and polyvinylacetate PVAc. Superposition of the short time portion of the softening transitions of the retardation spectra of PMA, PVAc, polystyrene, and amorphous polypropylene APP indicates that the local molecular mobility is a constant atTgwithin experimental uncertainty. The general features of the retardation spectra of linear amorphous polymers are discussed.

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260301

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractA high molecular weight poly(N‐acryloyl‐m‐aminobenzoic acid) (PMAB) was synthesized in a mixed solvent medium by radical polymerization. The polymer was separated into different fractions by fractional precipitation. All those eight fractions were characterized by viscometry, vapor pressure osmometry and gel permeation chromatography. Mark‐Houwink‐Kuhn‐Sakurada relationships were established for three different solvents at 30°C. Unperturbed dimensions were estimated from the viscosity‐molecular weight data using graphical methods based on approximate theories of Stockmayer and Fixman, and of Kurata, Stockmayer, and Roig, and on a first‐order perturbation treatment of the excluded volume effect. The results indicate that the PMAB chain is of interm

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260302

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe KAHR model of structural relaxation has been extended to include the effects of pressure upon the retardation times of glass‐forming materials. The previously used methodology is applied with a continuous distribution of retardation times of the fractional exponential form. Several forms of the pressure dependence are examined. The combined temperature and pressure changes on structural recovery of glasses are addressed in this pape

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260303

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractMorphological studies are reported for a thermotropic liquid crystalline polyester. Small angle light scattering studies were carried out as a function of temperature usingHvandVvpolarization with photographic as well as photometric techniques. No scattering was observed from a thin film cast from a dilute solution of the polymer in a highly volatile solvent. When the film was heated, scattering of light was observed above the glass transition temperature of the polyester. The scattering was found to be azimuthally dependent withVvintensities being much higher than the correspondingHvintensities. The size of the morphological features responsible for SALS patterns were calculated and were found not to change significantly with temperature ranging from glass transition temperature to the solid‐nematic transition temperature of the polyester. The WAXS pattern of solution cast polymer was representative of an amorphous structure. Solution cast films heat treated under various conditions (all above theTgof the polymer) contained crystalline as well as amorphous structures. The maximum apparent crystallinity for annealed samples was of the order of 30

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260304

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractMeasurements ofTlρas a function of temperature have been made on two polyethylene oxides (PEO) with molecular masses of 5,000 and 30,000. TheT1ρmeasurements show biexponential behavior of the relaxation function in the temperature range from 170 K to 350 K. The intensities of the components of the relaxation function are constant over this temperature range in agreement with the crystallinities of the samples. The two relaxation times can be associated with the crystalline and amorphous component; the relaxation time minima describe the α relaxation in the crystalline regions of PEO and the glass transition in amorphous P

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260305

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractElectron spin resonance (ESR) investigations of line shapes and radical decay behavior have been made on an epoxy based on tetraglycidyl diaminodiphenyl methane (TGDDM)/diaminodiphenyl sulfone (DDS), T‐300 graphite fiber, and T‐300/5208 (graphite fiber/epoxy) composites after irradiation with Co60γ‐radiation or 0.5 MeV electrons. Two kinetically distinct radical species are found in the irradiated epoxy as the temperature is raised beyond 120 K following irradiation of samples at 77 K with Co60γ. One has been termed a fast‐decaying species and the other a slow‐decaying species. The ratio of fast‐decaying/slow‐decaying radicals increases as the decay temperature rises. The fast‐decaying radicals at room temperature are attributed largely to alkyl type radicals residing in regions of relatively low crosslink density, while the long‐lived radicals are attributed to radicals residing in the highly crosslinked regions of the epoxy. A large concentration (ca. 1020to 1021spins/g) of unpaired electrons was found in unirradiated graphite fiber which masked the ESR spectral change in ir

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260306

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThermal properties of an anisotropic biaxially oriented Poly(ethylene terephthalate) (PET) were determined before and after further deformation of the Mylar film. Film shrinkage in different planar directions was monitored during and following initial heating. After stabilization for three days at 140°C, glass temperatures Tgwere determined from the decrease in length of film strips and were found to vary in the different in‐plane directions. An increase in anisotropy brought about by additional deformation in the direction of the greatest orientation enhanced the Tgdifference from 8 to 16°C. Tgis highest in the direction of greatest orientat

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260307

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractElongational creep measurements were carried out on a biaxially oriented poly (ethylene terephthalate) (PET) film parallel to, orthogonal to, and at 45° to the principal optic axis. Measurements made after various thermal treatments which were intended to stabilize the physical state of the PET were shown to be ineffective. Samples were annealed at 140°C for 12 days and aged at 95°C for over 24 days before measurement without success. Thermal cycling between 41 and 91°C which was also employed to stabilize the mechanical response also failed. Significant deceleration of the creep rate caused by densification of amorphous regions of the samples during storage below the glass temperatureTgis illustrated. Because of physical aging belowTgand morphological changes occurring aboveTgduring the various thermal treatments and histories, time‐scale shift factors were found to be not u

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260308

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe dynamic mechanical properties of partly sulfonated (8.1 mole%) polystyrene were investigated at a frequency of ca. 1 Hz, following neutralization with various low molecular weight flexible and rigid amines. IR spectroscopic evidence suggested that the protonated amine units were possibly H‐bonded to the sulfonate anion. Neutralization with flexible amines was found to result in a decrease in the glass transition temperatureTgby an amount proportional to the number of carbon atoms in the amine, while neutralization with rigid amines was found to result in an increase inTg. It was also observed that the amines were more miscible with the sulfonated material than with polystyrene. It was concluded that the changes in properties observed upon neutralization are similar to those expected from a graf

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260309

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractComblike polymethacrylates with oligo‐oxyethylene side chains were synthesized from the commercially available monomers CH2 C (CH3) COO (CH2CH2O)nCH3, the averagenbeing 4, 8, and 22. The three polymers exhibited lower critical solution temperatures in aqueous media. Cloud points were determined as a function of the nature and concentration of salt. For salts that destabilize the polymer solutions, the cloud points decrease linearly with salt concentration, the extent of the decrease being strongly anion dependent. Salt effects on the viscosity of the polymers were measured in water, methanol, and acetonitrile. In water the viscosity decreases on adding salt, but in methanol and acetonitrile the neutral polymers are converted to polycations as cations form stable adducts with the oligo‐oxyethylene side chains. The increase in viscosity is both cation and anion dependent. The general behavior of the comblike polymers resembles that reported for aqueous or methanolic salt solutions of poly (ethylene oxide) and nonionic surfac

ISSN:0887-6266    

DOI:10.1002/polb.1988.090260310

出版商:John Wiley&Sons, Inc.    

年代:1988

数据来源: WILEY