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Dried Film (dried + film)

Distribution by Scientific Domains
Polymers and Materials Science50%

Selected Abstracts

Hydration of polysaccharide hyaluronan observed by IR spectrometry.

BIOPOLYMERS, Issue 1 2003

Abstract This article is the first one in a series dedicated to the study of hyaluronan as observed by IR spectrometry. The goal is to determine its hydration mechanism and the structural changes this mechanism implies. Hyaluronan is a natural polysaccharide that is widely used in biomedical applications and cosmetics. Its macroscopic properties are significantly dependent on its degree of hydration. In this article we record the IR spectrum of a several micron thick dried film and deduce that four or five residual H2O molecules remain around each disaccharide repeat unit in the dried film. We then compare the spectra of sodium hyaluronan and its acid form to assign vibrational bands linked to the carboxylate group. We proceed with a qualitative analysis of the spectral changes induced by changes of temperature and hygroscopicity, two independent parameters that act by modifying the hydrogen bond network of the sample. This enables us to assign most of the vibrational bands of the hydrophilic groups and to distinguish the bands that are due to these hydrophilic groups when they are or are not hydrogen bonded. It constitutes a prerequisite for the quantitative analysis of hydration spectra that will be described in the following articles of this series. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 10,20, 2003 [source]

Characterization of PVA and Chitosan/PVA Blends Prepared from Aqueous Solutions of Various Na2SO4 Concentrations

MACROMOLECULAR SYMPOSIA, Issue 1 2006
Petronela Drambei
Abstract Uniplaner orientation of a particular crystal plane along the surface of a film was investigated for poly (vinyl alcohol) (PVA) film prepared by a coagulation bath with concentrated aqueous solution containing 100,,,300g of Na2SO4 against 1 , of water. The orientation distribution functions of the three crystallographic principal axes of the dried films were obtained by the X-ray diffraction technique. The same treatment was carried out for the films prepared by stretching biaxially of the fresh gel and then by drying the resultant fresh gel. The very high preferential orientation of the crystal chain axes and amorphous chain segments could be realized by the biaxially elongation. Accordingly, the techniques were applied to the biaxially stretching of chitosan and PVA blend films with high Young's modulus. The planer orientation of the chain axes of chitosan and PVA crystallites could be confirmed. The morphology of the film surface was estimated by measurements of contact angle and electron spectroscopy for chemical analysis. The results suggested that the admixture of chitosan decreases wet ability of the specimen and this tendency was slightly enhanced by the biaxially elongation. [source]

Comparison of properties of acrylic,polyurethane hybrid emulsions prepared by batch and semibatch processes with monomer emulsion feed

POLYMER INTERNATIONAL, Issue 5 2003
ebenik
Abstract Aqueous acrylic,polyurethane hybrid emulsions were prepared by batch and semibatch polymerization of acrylic monomer mixtures (butyl acrylate, methyl methacrylate and acrylic acid) in the presence of polyurethane dispersion. The acrylic component was introduced in the monomer emulsion feed. The weight ratio between acrylic and polyurethane components was varied to obtain different emulsion properties, microphase structure and mechanical film properties. Scanning electron microscopy, average particle size and molecular weight measurements were performed to characterize the latex systems. Mechanical properties were examined by measuring Koenig hardnesses of dried films. The average particle size increased with the acrylic/polyurethane ratio. Particles of larger than average size and, to some extent, higher than average molecular weights by batch process were formed. Koenig hardnesses decreased with increasing acrylic/polyurethane ratio. Properties of emulsions synthesized by semibatch processes were compared with the results reported for a different polyurethane dispersion. Copyright © 2003 Society of Chemical Industry [source]