Showing papers on "Vinyl alcohol published in 1991"

Preparation and Characterization of High‐Temperature Thermally Stable Alumina Composite Membrane

Abstract: A crack- and pinhole-free composite membrane consisting of an α-alumina support and a modified γ-alumina top layer which is thermally stable up to 1100°C was prepared by the sol–gel method. The supported thermally stable top layer was made by dipcoating the support with a boehmite sol doped with lanthanum nitrate. The temperature effects on the microstructure of the (supported and unsupported) La-doped top layers were compared with those of a common γ-alumina membrane (without doping with lanthanum), using the gas permeability and nitrogen adsorption porosimetry data. After sintering at 1100°C for 30 h, the average pore diameter of the La-doped alumina top layer was 17 nm, compared to 109 nm for the common alumina top layer. Addition of poly(vinyl alcohol) to the colloid boehmite precursor solution prevented formation of defects in the γ-alumina top layer. After sintering at temperatures higher than 900°C, the common alumina top layer with addition of poly(vinyl alcohol) exhibits a bimodal pore distribution. The La-doped alumina top layer (also with addition of poly(vinyl alcohol)) retains a monopore distribution after sintering at 1200°C.

Effect of the incorporation of amino groups in a glucose‐responsive polymer complex having phenylboronic acid moieties

Abstract: A novel polymer complex system sensitive to glucose was studied as a candidate material for formulating a chemically regulated insulin release system. A ternary copolymer of N-vinyl-2-pyrrolidone (NVP), 3-acrylamidophenylboronic acid (AAm-PBA) and N,N-dimethylaminopropylacrylamide (DMAPAA) (poly(NVP-co-PBA-co-DMAPAA)) was synthesized by radical copolymerization. The phenylboronic acid group in this copolymer serves as a glucose sensor moiety. Poly(NVP-co-PBA-co-DMAPAA) was soluble in water in the pH range of 3–12, in sharp contrast to a binary copolymer of NVP and AAm-PBA (poly(NVP-co-PBA)) which showed solubility only under alkaline aqueous conditions, where the boronic acid group is in a tetrahedral ionized form. The protonated amino group in poly(NVP-co-PBA-DMAPAA) contributed to increase the solubility of the polymer under physiological and acidic aqueous conditions. Furthermore, poly(NVP-co-PBA-co-DMAPAA) formed a stable polymer complex gel with poly(vinyl alcohol) (PVA) in pH 7.4 phosphate buffered solution due to the formation of a covalent linkage between the boronic acid groups in ternary copolymer and diol units in PVA. The release of myoglobin as model protein from the complex gel was increased immediately after the addition of glucose, due to the transition of gel into sol state, indicating the feasibility of this complex gel as a candidate material for a glucose-responsive delivery system for insulin.

Well-defined ethylene-vinyl alcohol copolymers via hydroboration: control of composition and distribution of the hydroxyl groups on the polymer backbone

Abstract: Cyclic olefins having different ring sizes were polymerized by ring-opening metathesis polymerization to give polyalkenylenes that have double bonds separated by varying numbers of methylene units. Upon hydroboration followed by oxidation, these polyalkenylenes yielded linear ethylene-vinyl alcohol copolymers whose vinyl alcohol content varied from 16 to 50 mol%. The melting points of these copolymers go through a minimum at a composition of ∼40 mol% vinyl alcohol. At higher ethylene content the melting point approaches that of linear high-density polyethylene

Immobilization of poly(ethylene glycol) onto a poly(vinyl alcohol) hydrogel. 1. Synthesis and characterization

Abstract: PEGs were immobilized onto a poly(vinyl alcohol) hydrogel using either acetal or urethane linkages. The hydrogel was crosslinked with glutaraldehyde using MgCl 2 (water based) or toluenesulfonic acid (DMSO based) as the acid catalyst. Fully hydrated gels prepared from DMSO had a lower compression modulus than those prepared from water although both materials possessed similar water contents.

Separation of liquid mixtures by using polymer membranes. III. Water–alcohol separation by pervaporation through modified PAN membrane

Abstract: A membrane was designed for the separation of a water–alcohol mixture by pervaporation on the basis of the difference in hydrogen-bonding interaction between two components of the membrane. Two kinds of poly(vinyl alcohol)-g-maleic anhydride/methyl methacrylate membrane were prepared by different methods: (1) A homogeneous membrane was formed by casting from dimethyl sulfoxide solution after purification. (2) A porous membrane was obtained directly by casting from the reaction solution, and then was purified. It is found that water was permeated through a homogeneous membrane preferentially in all ranges of feed compositions. Moreover, the flux was found to decrease with increasing PVA content in the membrane. The porous membrane after heat treatment has selective permeability for methanol. Pervaporation of water was investigated with respect to the feed concentration and also to the operating conditions. The effect of the molecular size of the permeating species on both permeation and separation is also discussed.

X-ray photoelectron spectroscopy and x-ray emission spectroscopy of poly(ethylene oxide) and poly(vinyl alcohol): experiment and theory

Abstract: XES and XPS measurements of valence band spectra of poly(ethylene oxide) and poly(vinyl alcohol) are reported. With the help of ab initio quantum chemistry calculations, some of the observed differences in line intensities and position are interpreted in terms of configurational differences in the polymeric units

Melt-molded articles and laminates derived therefrom, and their use

Abstract: A melt-molded article such as water soluble fibers, a laminate and a container for waste matter, the article having biodegradability. The melt molded article is produced by melt-molding a composition comprising an oxyalkylene group-containing vinyl alcohol copolymer and starch or a starch-derived macromolecular substance.

Studies on the preparation and properties of conductive polymers. III. Metallized polymer films by retroplating out

Abstract: A novel method to prepare polymer metallized films was found by using polymer metal chelate films treated with wetted metal plates (or metal powders). The polymer metal chelate films were prepared by metal salts mixed with the polymers containing a functional group, such as poly(vinyl alcohol) (PVA), polyamide, polyacrylamide (PAAm), and polyurethane (PU). This novel method is called the retroplating-out method. Polymer metallized films exhibited low surface resistivity around 10−1 Ω/cm2 by using this novel method. The surfaces of these films were shown to be metallized by means of X-ray analysis. The conduction mechanism was verified reasonably well by using scanning electron microscope (SEM) and UV-visible absorption data.

Biodegradable, liquid impervious films

Abstract: Liquid impervious, biodegradable films are disclosed. In particular, the films comprise a blend of an interpenetrated network of destructurized starch with ethylene/acrylic acid copolymers or ethylene/vinyl alcohol copolymers, and an aliphatic polyester such as polycaprolactone. Diapers, sanitary napkins, pantiliners, and the like, containing backsheets prepared from the foregoing materials are also disclosed.

Articles having a hydrophilic polymeric shell and method for preparing same

Abstract: Articles having a complex geometric configuration have hydrophilicity imparted to at least a portion of surfaces of the articles while substantially retaining the complex geometric configuration. The hydrophilicity is imparted by an extremely thin, self-interlocking shell of tactic, hydrophilic poly(vinyl alcohol) enveloping the surfaces. A tactic poly(vinyl alcohol) precursor applied to surfaces of the supporting structure is reacted in situ on the surfaces with a hydrolysis reagent to prepare the tactic, hydrophilic poly(vinyl alcohol) shell. The article having the hydrophilic shell is highly resistant to solvent washout. Hydrophilicity and hydrophobicity can be reversibly provided on regio-specific surfaces of the article. Articles in the form of membranes useful as filters, residue barriers for electroplating devices, separators for electrochemical cells, and drug delivery device components are also described. Membranes to form permanent and undistorted images, and methods of preparing such images from image-forming substances in receptive media are also provided. Hydrophilic porous supporting structures loaded with an enzyme system which catalyzes a reaction of a substrate, oxygen, and if necessary, water or moisture to consume oxygen are also described for oxygen scavenging in packages containing oxygen sensitive products.

Amine functional polymers containing acetal groups

Abstract: Polyvinylaminals, optionally as the formed copolymer with polyvinylhemiaminals, and polyvinylacetals are useful as flocculants and epoxy resin and polyurethane crosslinking agents and are provided by reacting a poly(vinylamine) or a copolymer containing vinyl alcohol and vinylamine units with a monoaldehyde. The aldehyde, such as butyraldehyde, can be introduced into the polymer acetalization as a liquid or gas, generally in a proportion of about 0.02 to 0.5 mol per mol of alcohol and amine units in the polymer chain.

Preparation and properties of barium sulphate and methyl iothalamate loaded poly(vinyl alcohol) microspheres as radiopaque particulate emboli

Abstract: Poly(vinyl alcohol) (PVA) microspheres impregnated with barium sulphate and methyl iothalamate, having diameters raning from 100 to 1500 μm were prepared by the glutaraldehyde cross-linking of an aqueous dispersion of PVA containing the radiopaques in paraffin oil using dioctyl sulfosuccinate (DOS) as the stabilizing agent and thionyl chloride as the catalyst. while the use of thionyl chloride allowed the formation of spherical, nonaggregatory beads, other catalysts such as magnesium chloride and hydrochloric acid gave rise to an agglomerated product. The radiopaques were found to be firmly trapped inside the microspheres as they did not leach out on prolonged standing in water, on sonication, or on steam sterilization. Microspheres with pores and channels were also made by incorporating a fine powder of methyl methacrylate along with barium sulphate during their preparation and washing out the polymer after the microspheres were formed. The porous nature of such microspheres was confirmed by transmission electron microscopy (TEM). Microspheres containing the radiopaques exhibited hydrophilicity, swelling ability, and compressibility to a significant extent. the radiopaque nature of the microspheres was confirmed by their x-ray images. In vitro tests using heparinized calf blood showed that the microspheres were nonhaemolytic in nature. These microspheres may find application as radiopaque emboli in particulate embolization.

Oxidation-resistant ethylene vinyl alcohol polymer compositions

Abstract: A composition of a copolymer of ethylene and vinyl alcohol, 0.01 to 0.5 weight percent of a monovalent or divalent metal salt of an aliphatic carboxylic acid having 3 to 9 carbon atoms and 0.05 to 0.5 weight percent of a hindered phenolic antioxidant exhibits improved stability toward oxidative gel formation at elevated temperatures.

XPS and SSIMS analysis of polymers: The effect of remote nitrogen plasma treatment on polyethylene, poly(ethylene vinyl alcohol) and poly(ethylene terephthalate)

Abstract: A study has been undertaken in which both x-ray photoelectron spectroscopy (XPS) and Fast atom bombardment static secondary ion mass spectrometry (FAB-SSIMS) have been used to study the effects of remote nitrogen plasma treatment on polymers such as linear low-density polyethylene (LLDPE), poly(ethylene vinyl alcohol) (EVOH) and poly(ethylene terephthalate) (PET). For comparison, remote oxygen plasma treatment was also performed on LLDPE. A very rapid uptake of nitrogen was observed for all polymers. Negative FAB-SSIMS indicated CN−, CNO− and C2N fragments on each of the nitrogen plasma-treated polmers. Positive FAB-SSIMS spectra of plasma-treated LLDPE showed relatively high intensity, high mass fragments, thought to originate from additives. These were not observed for the other two polymers. Significant amounts of aromatic-type fragments were observed in the positive FAB-SSIMS spectra of all treated polymers. Surface stability studies have shown that for both nitrogen and oxygen plasma-treaed LLDPE there is a substantial decrease in the surface functionality on exposure to air. This effect was much less prevalent for EVOH and PET.

Disposable absorbent articles with biodegradable backsheets

Abstract: Liquid impervious, biodegradable films are disclosed. In particular, the films comprise a blend of an interpenetrated network of destucturized starch with ethylene/acrylic acid copolymers or ethylene/vinyl alcohol copolymers, and an aliphatic polyester such as polycaprolactone. Diapers, sanitary napkins, pantiliners, and the like, containing backsheets prepared from the foregoing materials are also disclosed.

Miscibility of poly(vinyl alcohol)/poly(methacrylic acid) and poly(vinyl alcohol/poly(acrylic acid) systems. II. High-resolution solid-state CP/MAS 13C NMR studies.

Abstract: Miscibility of poly(vinyl alcohol)/poly(methacrylic acid) complexes and poly(vinyl alcohol)/poly(acrylic acid) blends is investigated by high-resolution 13C solid-state NMR method. Observed 13C spectra are discussed in terms of hydrogen-bonding effects on chemical shift. The results indicate that poly(vinyl alcohol) and poly(methacrylic acid) are intimately mixed on a scale of 20–30 A due to intermolecular hydrogen bonding to form equimolar-ratio complexes. For the poly(vinyl alcohol)/poly(acrylic acid)=1/1 blend, the two polymers are also miscible, the crystalline phase of PVA is destroyed completely and no detectable domain can be observed for the blend on a scale of 20–30 A. Poly(vinyl alcohol)/poly(acrylic acid)=2/1 and 1/2 blends are homogenous on a scale of 200–300 A, but heterogeneous on a smaller scale.

Interpolymer association between poly(acrylic acid) and vinyl alcohol-vinyl acetate copolymers in dilute aqueous solutions

Abstract: Interpolymer association and complexation between poly(acrylic acid) and vinyl alcohol-vinyl acetate copolymers (PVAL-AC) in dilute aqueous solutions were investigated by means of reduced viscosity and pH measurements. The influence of the degree of saponification of PVAL-AC and of the molecular weight of both polymers on complexation were examined. The viscosity measurements show the formation of gel-like or compact complexes and that association is strongly increased by the presence of acetate units in the PVAL-AC copolymer. The degree of complexation was calculated from the results of pH measurements. Some special aspects of the two different experimental approaches are discussed.