The ‘solution technique’ modification of poly(vinyl alcohol) (PVA) using maleic acid was carried out with the help of triethanolamine/water catalysts The resulting PVA membranes were characterized by differential scanning calorimetry, infrared spectroscopy, and tensile studies to investigate the reaction between PVA polymer and maleic acid It was found that the resulting PVA membranes had two portions, branched and crosslinked, and there were no more branched than cross-linked portions For the pervaporation separation of the acetic acid-water system, two reaction densities (Xcr = mole maleic acid per mole monomeric unit of PVA) of 005 and 01 were studied for the separation of the entire range of mixture compositions at 25° C The separation factors of the Xcr = 005 modified PVA membranes were higher than those of the Xcr 01 modified ones and the highest separation factor of 780 was obtained at 70wt% water in the feed with the Xcr = 005 modified PVA membrane

Modification of poly(vinyl alcohol) using maleic acid and its application to the separation of acetic acid-water mixtures by the pervaporation technique

Photocatalytic systems with light-sensitive coordination compounds and possibilities of their spectroscopic sensitization—an overview

( I ) Theoretical principles of the sensitization process. (2) Photosensitized polymerisation, graft polymerisation and cross-linking. Mercury-photosensitized reactions. Ion-pair complexes as photoinitiators. Photopolymerisation in the presence of metallic oxides. Photosensitization by chlorine, bromine and iodine compounds. Organic compounds as sensitizers. Halogenated compounds as sensitizers. Sensitizing compounds with the C=O group. Sensitizing compounds with t h e O U g r o u p . Sensitizing compounds containing nitrogen. Sulphur containing sensitizers. Reactions photosensitized by dyes. (3) Photosensitized cis-trans isomerization of polymers. (4) Photosensitized degradation. (S) Photopolymers. (6) Photosensitizing polymers. (7) Spectral sensitization of the photoeffect in polymers.

Photosensitized processes in polymer chemistry: a review

Application of ESCA to evaluate wood and cellulose surfaces modified by aqueous chromium trioxide treatment

A poly(vinyl alcohol) (PVA) membrane containing iron (Fe0) particles was developed and tested as a model barrier for contaminant containment. Carbon tetrachloride, copper (Cu2+), nitrobenzene, 4-nitroacetophenone, and chromate (CrO42-) were selected as model contaminants. Compared with a pure PVA membrane, the Fe0/PVA membrane can increase the breakthrough lag time for Cu2+ and carbon tetrachloride by more than 100-fold. The increase in the lag time was smaller for nitrobenzene and 4-nitroacetophenone, which stoichiometrically require more iron and for which the PVA membrane has a higher permeability. The effect of Fe0 was even smaller for CrO42- because of its slow reaction. Forty-five percent of the iron, based on the content in the dry membrane prior to hydration, was consumed by reaction with Cu2+ and 15% by reaction with carbon tetrachloride. Similarly, 25%, 17%, and 6% of the iron was consumed by nitrobenzene, 4-nitroacetophenone, and CrO42-, respectively. These percentages approximately double when...

/pdf/a-polymer-membrane-containing-fe0-as-a-contaminant-barrier-4wtc2vuxv9.pdf

A Polymer Membrane Containing Fe0 as a Contaminant Barrier

The insolubilization of polyvinyl alcohol by potassium dichromate on exposure to light has been investigated. Ultraviolet spectrometry shows that secondary hydroxyl groups are oxidized to ketone groups but insolubilization is attributed to crosslinking of polymer chains by co-ordination of alcohol groups to “nascent” chromic ions formed by reduction of the dichromate. Exposure to air saturated with water vapor eliminates the carbonyl absorption maxima from the ultraviolet spectrum of polyvinyl alcohol film but the spectrum can be restored by heating: this phenomenon is independent of the crosslinking reaction.

Light-sensitized crosslinking of polyvinyl alcohol by chromium compounds

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Light-sensitized crosslinking of polyvinyl alcohol by chromium compounds