Showing papers on "Vinyl acetate published in 2011"
TL;DR: In vitro drug release evaluations showed that both the kind of polymer and the amount of drug loaded greatly affected the degree of swelling, weight loss, and initial burst and rate of drug release, and the thickness of the blend nanofiber mats strongly influenced the initial release and rateof drug release.
Abstract: The aim of this study was to develop novel biomedicated nanofiber electrospun mats for controlled drug release, especially drug release directly to an injury site to accelerate wound healing. Nanofibers of poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), and a 50:50 composite blend, loaded with ciprofloxacin HCl (CipHCl), were successfully prepared by an electrospinning technique for the first time. The morphology and average diameter of the electrospun nanofibers were investigated by scanning electron microscopy. X-ray diffraction studies indicated an amorphous distribution of the drug inside the nanofiber blend. Introducing the drug into polymeric solutions significantly decreased solution viscosities as well as nanofiber diameter. In vitro drug release evaluations showed that both the kind of polymer and the amount of drug loaded greatly affected the degree of swelling, weight loss, and initial burst and rate of drug release. Blending PVA and PVAc exhibited a useful and convenient method for electrospinning in order to control the rate and period of drug release in wound healing applications. Also, the thickness of the blend nanofiber mats strongly influenced the initial release and rate of drug release.
349 citations
TL;DR: In this paper, two types of commercially applied Ethylene/Vinyl Acetate Copolymers (EVA) for encapsulation of photovoltaic modules were investigated by the thermal analysis methods of Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) in the temperature range from −150°C to 200°C.
146 citations
TL;DR: The Simulator of the Human Intestinal Microbial Ecosystem (SHIME) used to evaluate the stability of EVA during gastrointestinal transit showed that EVA was not modified during GI transit, nor did it affect the GI ecosystem following oral administration.
144 citations
TL;DR: In this paper, a series of different monomers, including acrylamides, acrylates, and vinyl acetate, were polymerized to high conversions at temperatures between 70 and 100 °C using various initiators, solvents, and RAFT agents.
121 citations
TL;DR: In situ reduction of graphene oxide (GO) at moderate temperatures within a polymer was observed using differential scanning calorimetry (DSC) as discussed by the authors, demonstrating that the polymer chemistry strongly influences the extent of reduction.
Abstract: In situ reduction of graphene oxide (GO) at moderate temperatures within a polymer was observed using differential scanning calorimetry (DSC). Comparison of heats of reduction from DSC data in poly(vinylpyrrolidone), poly(vinyl acetate), and poly(vinylpyrrolidone/vinyl acetate) nanocomposites demonstrates that the polymer chemistry strongly influences the extent of reduction. These results are compared to the time–temperature relationship for GO reduction in air and in dimethylformamide at the same temperatures, determined through changes in the atomic carbon-to-oxygen ratio. GO reduction was independently confirmed by electrical conductivity and optical absorption measurements, as well as Raman spectroscopy. These results show that GO sheets are reduced depending on the time–temperature history and polymer chemistry at the particles’ location. For nanocomposites this can lead to improvement or reduction of desired properties and is thus pertinent to thermal processing of polymer nanocomposites based on f...
99 citations
TL;DR: In this article, polymeric blend membranes were prepared from acrylonitrile-butadiene-styrene (ABS) and poly vinyl acetate (PVAc), and their CO 2/N2 and CO2/CH4 separation characteristics were investigated.
91 citations
TL;DR: In this paper, the synthesis of poly(vinylidene fluoride-co-3,3, 3-trifluoropropene)-b-oligo (vinyl alcohol) block copolymers by sequential controlled radical copolymerization of VDF and TFP in the presence of xanthate and their use as original surfactants are presented.
Abstract: The synthesis of poly(vinylidene fluoride-co-3,3,3-trifluoropropene)-b-oligo(vinyl alcohol) block copolymers by sequential controlled radical copolymerization of vinylidene fluoride (VDF) and 3,3,3-trifluoropropene (TFP) and of vinyl acetate in the presence of xanthate and their use as original surfactants are presented. First, a fluorinated xanthate C6F13C2H4OC(O)CH(CH3)SC(S)OC2H5 was prepared in two steps from 1H,1H,2H,2H-perfluorooctanol in 67% overall yield. Then, it was successfully involved as a chain transfer agent for the macromolecular design via the interchange of xanthates (MADIX) polymerization of vinyl acetate in a fluorinated solvent in 71% yield, and a good agreement was noted between targeted and experimental molecular weights of poly(vinyl acetate). This fluorinated xanthate was also successfully used in the radical copolymerization of VDF and TFP. Then, these poly(VDF-co-TFP) copolymers bearing a xanthate end group were involved in the controlled radical polymerization of vinyl acetate (...
85 citations
TL;DR: In this paper, the optical properties of the nanocomposite films were characterized from the analysis of the experimentally recorded transmittance and reflectance data in the spectral wavelength range of 300-800 nm.
Abstract: Poly (vinyl acetate) (PVAc) loaded bismuth oxide (Bi2O3) nanorods were successfully prepared at ambient pressure. X-ray diffraction (XRD) and transmission electron microscopy were used to characterize the final product. It was found that Bi2O3 nanorods were formed and the diameter of the rods was confined to about 8 nm. The diameter and length of formed rods were found to increase by increasing the bismuth oxide concentration in the PVAc matrix. The optical properties of the nanocomposite films were characterized from the analysis of the experimentally recorded transmittance and reflectance data in the spectral wavelength range of 300–800 nm. The values of some important parameters of the studied films are determined such as refractive index (n), extinction coefficient (k), optical absorption coefficient (α), and band energy gap (Eg). According to the analysis of dispersion curves, it has been found that the dispersion data obeyed the single oscillator of the Wemple–DiDomenico model, from which the dispersion parameters and high-frequency dielectric constant were determined. In such work, from the transmission spectra, the dielectric constant (e∞) and the third-order optical nonlinear susceptibility χ(3) were determined. Copyright © 2010 John Wiley & Sons, Ltd.
72 citations
TL;DR: The addition of an organic liquid to the xPVAc-borate HVPDs results in a drastic increase in the number of cross-linked borate species as well as the agglomeration of the polymer into bundles, which increases the relaxation time and thermal stability of the networks.
Abstract: A gel-like, high-viscosity polymeric dispersion (HVPD) based on cross-linked borate, partially hydrolyzed poly(vinyl acetate) (xPVAc, where x is the percent hydrolysis) is described. Unlike hydro-HVPDs prepared from poly(vinyl alcohol) (PVA) and borate, the liquid portion of these materials can be composed of up to 75% of an organic cosolvent because of the influence of residual acetate groups on the polymer backbone. The effects of the degree of hydrolysis, molecular weight, polymer and cross-linker concentrations, and type and amount of organic cosolvent on the rheological and structural properties of the materials are investigated. The stability of the systems is explored through rheological and melting-range studies. (11)B NMR and small-angle neutron scattering (SANS) are used to probe the structure of the dispersions. The addition of an organic liquid to the xPVAc-borate HVPDs results in a drastic increase in the number of cross-linked borate species as well as the agglomeration of the polymer into bundles. These effects result in an increase in the relaxation time and thermal stability of the networks. The ability to make xPVAc-borate HVPDs with very large amounts of and rather different organic liquids, with very different rheological properties that can be controlled easily, opens new possibilities for applications of PVAc-based dispersions.
65 citations
TL;DR: The effect of some direct compression excipients and lubricants on the adhesion of hydroxypropyl methyl cellulose films has been examined using a specially designed tensile testing apparatus and found to be influenced by both the roughness, including microporosity, of the tablet surface and its polarity.
Abstract: The effect of some direct compression excipients and lubricants on the adhesion of hydroxypropyl methyl cellulose films has been examined using a specially designed tensile testing apparatus (Fisher & Rowe, 1976). The adhesion was found to be influenced by both the roughness, including microporosity, of the tablet surface and its polarity. Tablets prepared from microcrystalline cellulose showed very high adhesions despite having relatively smooth surfaces, owing to the surface being saturated with hydroxyl groups able to form hydrogen bonds with the corresponding groups on the polymer. The addition of magnesium or calcium stearate to the tablet was found to decrease the adhesion, but the addition of stearic acid caused a significant increase. The effect of lubricant concentration on the adhesion could be expressed by an equation similar to that proposed by Hofrichter & McLaren (1948) for the adhesion of vinyl chloride/vinyl acetate copolymers to regenerated cellulose.
64 citations
TL;DR: In this paper, a reasonably linear relation was found between the VA content on the surface (wt.%) obtained from XPS analysis and the volume of VA content in bulk especially for PVAc/EVA-33 blend surfaces.
TL;DR: Results confirmed that use of different immobilization protocols may be a powerful tool for altering enzyme properties when used in organic media.
Abstract: In this work, we intend to check the effect of the immobilization protocol on the performance of lipase B from Candida antarctica (CalB) in organic medium. To this purpose, CalB has been immobilized on Eupergit C (EC) under different conditions and on EC partially modified with ethylenediamine (EDA), iminodiacetic acid (IDA) or metal chelate (IDA-Cu2+) and used for kinetic resolution of (R/S) 4-[2-hydroxy-3-[(1-methylethyl)amino]propoxy]benzeneacetamide (rac-atenolol). Enantiomeric resolution of atenolol was carried out by a transesterification reaction using vinyl acetate as acylant agent and an organic solvent as reaction medium. After a preliminary optimization of the reaction to obtain satisfactory yields, toluene was selected as the optimal solvent and the performances of the different CalB biocatalysts were compared. The R enantiomer was preferred in all cases but their performances were substantially different, with high differences in reaction rates, reaction yields in this kinetically controlled synthesis (EC-CalB gave a conversion of 76% while EC-IDA-Cu2+-CalB gave just a 27%), and enantiospecificities (EC-CalB gave an E value of 65 while EC-IDA-Cu2+-CalB gave a value of 13). Replacing toluene with hexane caused a decrease in enzyme activity, reaction yields and enantiospecificity of the reaction. It was remarkable that some preparations were much more sensitive to this solvent change than others. Considering that the activity decreased by less than 10% per reaction cycle, these differences are likely associated with the differences in the enzyme catalytic properties caused by the different immobilization protocols and not by inactivation of immobilized enzyme preparations during the reaction. These results confirmed that use of different immobilization protocols may be a powerful tool for altering enzyme properties when used in organic media.
TL;DR: In this paper, a gel-state electrolyte was fabricated by using poly(acrylonitrile -co-vinyl acetate) (PAN-VA) as the gelator of an 3-methoxypropionitrile (MPN)-based liquid electrolyte and was applied in dye-sensitized solar cells (DSSCs).
Abstract: A highly efficient gel-state electrolyte was fabricated by using poly(acrylonitrile -co-vinyl acetate) (PAN–VA) as the gelator of an 3-methoxypropionitrile (MPN)-based liquid electrolyte and was applied in dye-sensitized solar cells (DSSCs). The VA segaments act to dissolve the copolymer into the electrolyte, forming a gel-state structure. The electric conductivity of the gel-state electrolyte is comparable to that of the liquid electrolyte, attributed to the enhancement effect of the AN segments to the dissociation of LiI and 1-propyl-2,3-dimethylimidazolium iodide (DMPII). This effect also leads to a slightly downward shift of the TiO2 conduction band edge toward positive potentials. The energy conversion efficiency of the DSSC achieved by using this gel-electrolyte is 8.34%, which is 97% the value of the liquid-state cell (8.63%).
TL;DR: The preparation and structural characterization of a family of viscoelastic dispersions of borate cross-linked, 80% hydrolyzed poly(vinyl acetate) (80PVAc) in aqueous-organic liquids are presented and the results are used to assess their potential as low-impact cleaning agents for the surfaces of paintings.
Abstract: The preparation and structural characterization of a family of viscoelastic dispersions of borate cross-linked, 80% hydrolyzed poly(vinyl acetate) (80PVAc) in aqueous-organic liquids are presented. Correlations between mechanical properties (from rheological measurements) and the degree and nature of cross-linking (from (11)B NMR spectroscopy) are reported, and the results are used to assess their potential as low-impact cleaning agents for the surfaces of paintings. Because the dispersions can be prepared at room temperature by simple procedures from readily available materials and can contain up to 50% (w/w) of an organic liquid, they offer important advantages over previously described cleaning agents that are based on fully hydrolyzed PVAc (i.e., poly(vinyl alcohol). The mechanical properties of the various aqueous-organic dispersions, as determined quantitatively by rheological investigations and qualitatively by their ease of removal from a solid surface (i.e., the so-called "peel-off" ability) have been tuned systematically by varying the amount of organic liquid, its structure, and the concentrations of borax and 80PVAc. The (11)B NMR studies demonstrate that the concentration of borate ions actively participating in cross-linking increases significantly with the amount of organic liquid in the mixture. The degree of cross-linking remains constant when the 80PVAc and borax concentrations are varied, as long as their ratios are kept constant. Some of the 80PVAc-borax dispersions have been tested successfully as cleaning agents on the surface of a 16th-17th century oil-on-wood painting by Lodovico Cardi, "Il Cigoli", that was covered by a brown patina and on the surface of a Renaissance wall painting by Vecchietta in Santa Maria della Scala, Siena, Italy, that had a degraded polyacrylate coating from a previous conservation treatment.
TL;DR: In this article, a comparative study on the acetylation of maritime pine wood by reaction with vinyl acetate (VA) and acetic anhydride (AA) has been undertaken.
TL;DR: In this article, three different polyvinyl alcohol (PVA) polymers, with 12% vinyl acetate monomeric units and molar weights of 37,000, 67,000 and 130,000 were developed as potential scaffolds for regenerative medical applications.
Abstract: Fibrous meshes based on three different poly(vinyl alcohol) (PVA) polymers, with 12% vinyl acetate monomeric units and molar weights of 37,000, 67,000, and 130,000 were developed as potential scaffolds for regenerative medical applications. The meshes were electrospun and characterized by molecular weight, concentration, applied voltage, and needle—collector distance. The influence of feed rate and the electrodes configuration (needle-to-tip and screen-to-screen system) was determined. Highly porous, 3D structures composed of randomly oriented ultrafine fibers, with an average fiber diameter of a few hundred nanometers were developed. Solutions of PVA and human serum albumin were successfully electrospun and the fibrous mesh was stabilized with glutaraldehyde. The influence of these operations on the mechanical properties was evaluated by uniaxial tensile testing.
TL;DR: Interestingly, the experimental results demonstrated catalytic activity of immobilized lipase to be 4-fold greater than that of free lipase for transesterification reaction.
Abstract: The film prepared using a blend of hydroxypropyl methyl cellulose (HPMC) and polyvinyl alcohol (PVA) was investigated for immobilization of Rhizopus oryzae lipase. These immobilized lipase films were characterized using a combination of techniques like SEM, TGA, FT-IR, and Karl Fischer titration analysis. The biocatalyst was subjected to transesterification reaction of benzyl alcohol with vinyl acetate and was optimized for various reaction parameters such as effect of support, molar ratio, solvent, concentration of biocatalyst, time and temperature. Furthermore, the developed methodology was then effectively applied to various alcohols for synthesis of industrially important acetates providing good to excellent yields of desired products. Interestingly, the experimental results demonstrated catalytic activity of immobilized lipase to be 4-fold greater than that of free lipase for transesterification reaction. The immobilized biocatalyst was effectively recycled for four consecutive cycles and exhibited r...
TL;DR: In this paper, the structure-property relationship between polyvinyl acetate-based polymers and their solubility in supercritical carbon dioxide was investigated, based on RAFT/MADIX polymerization.
TL;DR: In this paper, the performance of gel polymer electrolytes (GPEs) for lithium ion battery was studied by using a number of tools, such as scanning electron microscopy, thermogravimetric analyzer, electrochemical impedance spectroscopy, cyclic voltammetry, and charge/discharge test.
Patent•
17 Jun 2011TL;DR: In this paper, the authors proposed a method for the chemical vapor deposition of a composition including at least one monomer selected from the group consisting of N-vinyl pyrrolidone, vinyl acetate, ethylene oxide, alkyl acrylate and other mixtures thereof, and methods of making and using the same.
Abstract: This invention relates to medical articles, such as syringe assemblies, including a substrate having a coating on a surface thereof, the coating including: (1) at least one organopolysiloxane and (2) a deposition product applied to the at least one organopolysiloxane by plasma - enhanced chemical vapor deposition of a composition including at least one monomer selected from the group consisting of N-vinyl pyrrolidone, vinyl acetate, ethylene oxide, alkyl acrylate, alkyl methacrylate, acrylamide, acrylic acid, and mixtures thereof, and methods of making and using the same.
TL;DR: In this paper, the crystal growth rates of two chemically diverse organic drug molecules (bifonazole and nimesulide) from the undercooled melt regime close to the glass transition temperature were investigated.
Abstract: The purpose of this study was to understand how different polymers affect the crystal growth rates of two chemically diverse organic drug molecules (bifonazole and nimesulide) from the undercooled melt regime close to the glass transition temperature. Bifonazole is an antifungal drug that contains no traditional hydrogen bond donors, only acceptors. In contrast, nimesulide contains both hydrogen bond donor and acceptor groups. Therefore, the potential hydrogen bonding interactions with polymers vary between the two compounds. For bifonazole, poly(vinylpyrrolidone) (PVP), hydroxypropyl methylcellulose acetate succinate (HPMCAS), poly(vinylpyrrolidone-vinyl acetate) (PVP/VA) and poly(acrylic acid) (PAA) were investigated, while for nimesulide, PVP, PVP/VA and poly(vinyl acetate) (PVAc) were probed. Polymers were incorporated at a level of 5%w/w by cryomilling followed by melt quenching. Linear crystal growth rates in the presence and absence of polymers were measured as a function of temperature (18–100 °C for bifonazole and 18–80 °C for nimesulide) using optical microscopy. Differential scanning calorimetry (DSC) and infrared spectroscopy were performed for further characterization. All of the polymers decreased the growth rates of both drugs, however large differences could be observed between polymers in terms of the extent of crystal growth inhibition. For bifonazole, PAA was a notably better crystal growth inhibitor compared to the other polymers. This may be related to formation of specific interactions between the drug and the polymer. For nimesulide, the order of effectiveness was PVP∼PVP/VA>PVAc and, compared to bifonazole, differences seen between polymers were more modest. Infrared (IR) spectroscopy and density functional calculations strongly suggested that amorphous nimesulide formed an intramolecular hydrogen bond. IR spectroscopy showed that drug-polymer intermolecular hydrogen bonding did occur, but was hampered by the partial loss of the hydrogen bond donor to the intramolecular hydrogen bond. Hence the effectiveness of a polymer appears to depend not only on the chemistry of the drug, but also on the availability of hydrogen bonding groups.
TL;DR: In this paper, the synthesis of highly CO2-soluble stabilisers that overcome the current limitation requiring use of fluorinated or siloxane based materials for synthesis and processing is described.
01 Jan 2011
TL;DR: In this article, a discussion of the importance of the biodegradability of a certain polymer class cannot be made without understanding the impact that polymer class has on the environment and other issues, apart from the actual biodegradation mechanisms, other issues will be addressed.
Abstract: This chapter deals with the biodegradability of vinyl ester-based polymers with a special emphasis on poly(vinyl acetate) and poly(vinyl alcohol). A proper discussion of the importance of the biodegradability of a certain polymer class cannot be made without understanding the impact that polymer class has on the environment. Therefore, apart from discussing the actual biodegradation mechanisms, other issues will be addressed. These include, but are not limited to, how long the class of vinyl ester-based polymers has been known and produced on an industrial scale, what quantities are produced and released into the environment each year, and what applications are addressed with this polymer class. We will also look at the general physical and chemical properties of this polymer class and how these properties can influence biodegradability. After a discussion of what “biodegradability” actually means – and what not – the mechanisms for the biodegradation of poly(vinyl ester)s will be discussed in more detail and a summary given of the biological systems able to process poly(vinyl ester)s.
TL;DR: MIP was shown to be promising for regeneration without significant loss in adsorption capacity and demonstrated higher affinity for target BPA and BPA-analogues over other common water pollutants.
TL;DR: In this paper, a laboratory evaluation of conventional, fundamental, rheological, and morphological characteristics of styrene-butadiene-styrene (SBS) andethylene vinyl acetate (EVA) polymer modified bitumens is presented.
Abstract: Received 6 March 2010; accepted 28 January 2011DOI 10.1002/app.34282Published online 7 July 2011 in Wiley Online Library (wileyonlinelibrary.com).ABSTRACT: This article presents a laboratory evaluationof conventional, fundamental, rheological, and morpholog-ical characteristics of styrene-butadiene-styrene (SBS) andethylene vinyl acetate (EVA) polymer modified bitumens.Polymer modified bitumen (PMB) samples have been pro-duced by mixing a 50/70 penetration grade unmodified(base) bitumen with SBS and EVA copolymer at differentpolymer contents. The fundamental viscoelastic propertiesof the PMBs were determined using dynamic (oscillatory)mechanical analysis and presented in the form of tempera-ture and frequency-dependent rheological parameters.The morphology of the samples as well as the percentarea distribution of polymers throughout the base bitumenhave been characterized and determined by means offluorescent light optic microscopy and Qwin Plus imageanalysis software, respectively. The results indicated thatpolymer modification improved the conventional andrheological properties of the base bitumen. It was alsoconcluded that the temperature and frequency had a sig-nificant effect on complex modulus of PMBs. The behaviorof EVA and SBS PMBs had exhibited quite difference at50 C. Moreover, it was found out that at low polymercontents, the samples revealed the existence of dispersedpolymer particles in a continuous bitumen phase, whereasat high polymer contents a continuous polymer phase hasbeen observed.
TL;DR: In this paper, the effect of confinement on structural relaxation in ultrathin polyvinyl acetate (UPCA) films has been studied by local dielectric spectroscopy.
Abstract: The effect of confinement on structural relaxation in ultrathin poly(vinyl acetate) films has been studied by local dielectric spectroscopy. This scanning probe method allows the investigation of d...
TL;DR: One-step roll-to-roll lamination transfer of graphene was achieved by poly(ethylene co-vinyl acetate) as a binding material which has thermoplastic property and wide rubbery-plateau region between Tg~Tm.
Abstract: One-step roll-to-roll lamination transfer of graphene was achieved by poly(ethylene co-vinyl acetate) as a binding material which has thermoplastic property and wide rubbery-plateau region between Tg~Tm. The transferred graphene film has a transmittance of 96.7% at 550 nm and 1.96 kΩ/sq of sheet resistance measured by simple 4-probe method. Standard deviation was found to be 0.198 kΩ/sq.
TL;DR: In this article, an original xanthate possessing a vinyl ester polymerizable function, namely vinyl 2-[(ethoxycarbonothioyl)sulfanyl]propanoate (Xa2), was synthesized.
TL;DR: In this paper, the effect of different polyolefins, used as additives in small proportions, exert on the rheological properties of standard lithium lubricating greases was evaluated. But, the use of polyoles as rheology modifiers does not significantly affect the friction coefficient determined in a tribological contact.
TL;DR: In this paper, the photodegradation behavior of an ethylene-vinyl acetate copolymer (EVA)/low density polyethylene (LDPE) composite containing four different types of titanium dioxide (TiO 2 ) was investigated through color difference, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and mechanical tests.