Search results for "vinyl acetate"

Photo-oxidation of polyolefin/clay nanocomposite films: role of organoclay and matrix type

2009

SAXS investigation on aggregation phenomena in supercritical CO2.

2004

Synchrotron Small-Angle X-Ray scattering (SAXS) measurements on aggregate formation of a Polyvinyl acetate- b-Perfluoro octyl acrylate (PVAc- b-PFOA) block copolymer in supercritical CO(2) are here reported. Experiments were carried out for a series of different thermodynamic conditions, changing the solvent density by profiling both the pressure at constant temperature and the temperature at constant pressure. This block copolymer and in general fluorocarbon-hydrocarbon di-blocks form aggregates depending on the value of CO(2) density. A sharp transition between monomers dissolved as random coils and micelles characterized by a solvophilic shell and a solvophobic core occurs when the CO(2)…

Influence of PVP/VA copolymer composition on drug–polymer solubility

2015

In this study, the influence of copolymer composition on drug-polymer solubility was investigated. The solubility of the model drug celecoxib (CCX) in various polyvinylpyrrolidone/vinyl acetate (PVP/VA) copolymer compositions (70/30, 60/40, 50/50 and 30/70 w/w) and the pure homopolymers polyvinylpyrrolidone (PVP) and polyvinyl acetate (PVA) was predicted at 25 °C using a thermal analysis method based on the recrystallization of a supersaturated amorphous dispersion (recrystallization method). These solubilities were compared with a prediction based on the solubility of CCX in the liquid monomeric precursors of PVP/VA, N-vinylpyrrolidone (NVP) and vinyl acetate (VA), using the Flory-Huggins …

Preparation and characterization of antimicrobial polymeric films based on poly(ethylene-co-vinyl acetate)

2009

Proton conducting composite electrolytes based on antimonic acid

1997

Abstract This report concerns a composite proton electrolyte suitable for use in electrochromic devices. The electrolyte consists of nanosize pyrochlore antimonic acid particles suspended in a poly(vinyl acetate) matrix by a gel route. It was found possible to substitute the antimonic acid by inert oxides of aluminum and silicon, thus making the electrolyte less harmful to the oxide electrodes of the electrochromic devices without considerably decreasing the conductivity. The proton conductivity of the antimonic acid electrolyte was ∼10 −4 S/cm at room temperature, practically independent of its amount of absorbed water.

1980

Molecular weights of Trogamid T® were determined by ultracentrifugation, light-scattering, osmometry and viscometry, molecular weight distributions by gel permeation chromatography (GPC) and five different fractionation methods. The separation efficiency of GPC with N,N-dimethylformamide as solvent was tested with three different types of gels, crosslinked polystyrene, porous glass and crosslinked poly(vinyl acetate), the last one yielding the best results. Solution fractionations show better results than precipitation methods. All fractionations gave far too small apparent non-uniformities. After correction according to the non-uniformities of the fractions the results corresponded to thos…

Control of biofilm formation by poly-ethylene-co-vinyl acetate films incorporating nisin.

2010

The aim of this study was to evaluate the effect of poly-ethylene-co-vinyl acetate (EVA) films incorporating different concentrations (0.1%, 0.5% and 1%) of nisin on the biofilm-forming ability of Listeria monocytogenes ATCC 7644, Staphylococcus aureus 815 and Staphylococ-cus epidermidis ATCC 35984. Nisin was incorporated into two grades of EVA (EVA14 and EVA28) in the melt during a common film-blowing operation. The efficacy of EVA/nisin films was evaluated by biofilm biomass measurements and Live/Dead staining in combination with fluorescence microscopy. In order to evaluate whether the nisin incorporation could modify the film surface properties, contact angle measurements and scanning e…

Synthesis of Macromolecular Substances by Addition Polymerization

2001

As already explained, polymerization reactions can proceed by various mechanisms and can be catalyzed by initiators of different kinds. For addition polymerization of single compounds, initiation of chains may occur via radical, cationic, anionic, or so-called coordinative-acting initiators, but some monomers will not polymerize by more than one mechanism. Both thermodynamic and kinetic factors can be important, depending on the structure of the monomer and its electronic and steric situation. The most important initiators are summarized in Table 3.1.

Critical Micelle Density for the Self-Assembly of Block Copolymer Surfactants in Supercritical Carbon Dioxide

1999

The parameters which influence the self-assembly of molecules in solution include the temperature and solvent quality, and this study illustrates the use of these variables to regulate the degree of association of block copolymer amphiphiles in highly compressible supercritical carbon dioxide. Small-angle neutron scattering (SANS) has been used to examine the association behavior of a block copolymer containing a CO2-phobic moiety, poly(vinyl acetate), and a CO2-philic block, poly(1,1-dihydroperfluoro-octylacrylate). By adjustment of the density of the medium through pressure and temperature profiling, the self-assembly can be reversibly controlled from unimers to core−shell spherical micel…

Challenging Dogma: Thresholds for Genotoxic Carcinogens? The Case of Vinyl Acetate

2002

Although many questions remain unanswered, the general principle of the sequence of events leading to cancer after exposure to genotoxic carcinogens has become increasingly clear. This helps to understand the parameters that influence the shape of the dose-effect curve for carcinogenesis, including metabolic activation and inactivation of carcinogens, DNA repair, cell cycle control, apoptosis, and control by the immune system. A linear dose-response relationship with no observable threshold seems to be a conservative but adequate description for the carcinogenic activity of many genotoxic carcinogens, such as aflatoxin B1, the tobacco-specific nitrosoketone NNK, and probably N,N-diethylnit…