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The morphology in nafion perfluorinated membrane products, as determined by wide‐ and small‐angle x‐ray studies
Tập 19 Số 11 - Trang 1687-1704 - 1981
AbstractThe morphology of the ionomer resin from which Nafion perfluorinated
membrane products are made was studied with wide‐angle and small‐angle x‐ray
diffraction. A reflection observed in the small‐angle x‐ray scan from hydrolyzed
polymer is attributed to ionic clustering. The effects of equiv wt, cation form,
temperature, water content, and tensile drawing on this reflection were studied
and ...
Raman spectroscopic method for determining the crystallinity of polyethylene
Tập 16 Số 7 - Trang 1181-1193 - 1978
AbstractThe Raman spectrum of partially crystalline polyethylene can be
described as a superposition of three components, which originate from the
orthorhombic crystalline phase, a meltlike amorphous phase, and a disordered
phase of anisotropic nature, where chains are stretched but have lost their
lateral order. The mass fractions involved in the three phases can be derived
directly from the inte...
Solid state characterization of the structure of chitosan films
Tập 19 Số 7 - Trang 1081-1105 - 1981
AbstractFilms of chitosan, prepared by different fabrication processes, were
examined at several structural levels, from the molecular to the macroscopic.
This revealed the presence of polymorphic crystal forms, which varied with film
treatment. Similarly, morphological structures varying from spherulites to rods
were formed, depending on film processing conditions. The effect of structure on
the ...
Model of partial crystallization and melting derived from small‐angle X‐ray scattering and electron microscopic studies on low‐density polyethylene
Tập 18 Số 6 - Trang 1361-1381 - 1980
AbstractA temperature‐dependent small‐angle x‐ray scattering and electron
microscopic study on a sample of low‐density polyethylene affords a
determination of the structure changes in a heating and cooling cycle and
suggests a new model of partial crystallization and melting. The analysis of
SAXS data is based upon some general properties of the electron‐density
correlation function. Electron micr...
Dynamic mechanical studies of α and β relaxations of polyethylenes
Tập 22 Số 3 - Trang 407-448 - 1984
AbstractThe α and β relaxations of a variety of polyethylenes have been
extensively studied using lowfrequency dynamic mechanical methods. The main
focus of this work has been both the control and the quantitative measurement of
the key structural factors that describe semicrystalline polymer systems. The
structural factors that have been examined in detail include the level of
crystallinity, the ...
Supramolecular structure of a high‐modulus polyaromatic fiber (Kevlar 49)
Tập 15 Số 12 - Trang 2201-2211 - 1977
AbstractThe supramolecular organization of the aromatic polyamide fiber Kevlar
49 has been studied using a combination of electron diffraction and electron
microscope dark‐field image techniques. The dark‐field images derived using
selected reflections from longitudinal sections exhibit axial banding of two
main types having periodicities of 500 and 250 nm. Careful analysis, including
tilting expe...
An analysis of the crystallization behavior of poly(ethylene oxide)/poly(methyl methacrylate) blends by spectroscopic and calorimetric techniques
Tập 22 Số 7 - Trang 1331-1342 - 1984
AbstractInfrared spectra in conjunction with calorimetric measurements have been
used to follow the crystallization process and microstructural changes of
poly(ethylene oxide) (PEO) in poly(ethylene oxide) and poly(methyl methacrylate)
(PMMA) blends. We have given particular attention to compositions containing low
PEO concentrations. The crystallization behavior and the resultant
microstructures ...
Effects of high‐pressure CO2 on the glass transition temperature and mechanical properties of polystyrene
Tập 20 Số 8 - Trang 1371-1384 - 1982
AbstractHydrostatic pressure usually increases the glass transition temperature
Tg of a polymer glass by decreasing its free volume; if the pressurizing
environment is soluble in the polymer, however, one might expect an initial
decrease in Tg with pressure as the polymer is plasticized by the environment.
Just such a minimum in the Tg of polystyrene (PS) is observed as the pressure of
CO2 gas is ...
A model for permeation of mixed gases and vapors in glassy polymers
Tập 19 Số 10 - Trang 1513-1530 - 1981
AbstractA model is discussed which explains reported complex effects of feed
composition and pressure on component permeabilities in high‐pressure gas
separators based on glassy polymer membranes. A special form of Fick's law which
accounts for the fact that penetrants in glassy polymers sorb into and diffuse
through two different molecular environments provides the basis for the analysis
of gas m...
Some phenomenological consequences of the Doi–Edwards theory of viscoelasticity
Tập 18 Số 1 - Trang 27-34 - 1980
AbstractDoi and Edwards have recently proposed a molecular theory for the
dynamics of entangled polymer liquids based on a tube model to represent the
mutual constraints on configurational rearrangement of the chains. Expressions
for diffusion coefficient, plateau modulus, zero‐shear viscosity, steady‐state
recoverable compliance, and terminal relaxation time can be devloped, and
relations among t...