Search results for "ACETATE"
showing 10 items of 756 documents
Tomographic and Topographic Investigation of Poly-D,L-Lactide-Co-Glycolide Microspheres Loaded with Prostaglandine E<sub>2</sub> for Exte…
2010
Polymeric, biodegradable microspheres represent a good reliable system to investigate the release of bioactive substances in both in vitro and in vivo applications. Common biomaterials for the synthesis of these microspheres are aliphatic polyesters of the poly(α-hydroxy)acids, especially poly-L-lactides (PLA) and polyglycolides (PGA) or their copolymers poly-D,L-lactide-co-glycolides (PLGA). In our own previous studies we have developed PLGA microspheres with integrated PGE2 as model substance for a wide range of biomedical applications, especially in angiogenesis, fracture healing and cartilage repair. The synthesis is based on a binary solvent in water emulsion approach, where two differ…
EVA copolymer based nanocomposites: rheological behavior under shear and isothermal and non-isothermal elongational flow
2006
Abstract Nanocomposites are a very promising new class of polymer composites that exhibit an interesting combination of chemical, physical and mechanical properties. Only small amounts of nanofiller are sufficient to generate great variation of many properties. This work focuses on the rheological properties of poly[ethylene- co -(vinyl acetate)] (EVA copolymer) based nanocomposites in shear and in isothermal and non-isothermal elongational flow. The nanocomposites, at two different filler contents, were prepared in two different extruders and intercalates were obtained for all the samples. The twin-screw compounder is more efficient. The change of rheological properties, both in shear and …
Modeling and stress-strain characteristics of the mechanical properties of carbon-nanotube-reinforced poly(vinyl acetate) nanocomposites
2011
Polymer/carbon nanotube (CNT) composites are one of the most perspective advanced materials developed in recent years. The properties of CNT-reinforced polymer composites, however, strongly depend on structural aspects of the nanostructured filler and on its dispersion quality in a polymer matrix. Consequently, this research was devoted to the investigation of multiwalled-CNT-modified poly(vinyl acetate) (PVAc) composites with respect to the mechanical property dependence on some structural characteristics of CNTs. PVAc/CNT nanocomposites were obtained with a solution casting technique. The amount of CNTs was changed from 0.01 up to 2 wt %. The stress–strain characteristics of PVAc/CNT nano…
Composites of ethylene-vinyl acetate copolymers with modified magnesium hydroxide-thermo-oxidative ageing
2014
Flame retardant composites must perform their protective roles permanently, also under conditions of intermittent or long-term exposure to sunlight, moisture or increased temperature. The aim of our work was characterization of the thermo-oxidative ageing (90 °C) and the changes in flammability of ethylene-vinyl acetate copolymer composites with 40 and 60 wt.% of magnesium hydroxide. The neat polymer and its composites were investigated for their thermal (DSC) and structural (FTIR) characteristics as well as their density, melt flow index, tensile properties and combustibility during ageing test. As FTIR results identified the different carbonyl groups in copolymer were created, the highest…
Excess viscosity and glass transition
2001
Abstract Literature data on the viscosity of solutions of poly(butyl methacrylate) (PBMA) and poly(methyl methacrylate) (PMMA) in diethyl phthalate (DEP) for different temperatures, including the range around and below T g , the glass transition temperatures of the pure polymers, were evaluated by means of an approach that uses surface fractions as composition variables. The discussion of these results together with information on solutions of the isomeric polymers, poly(vinyl acetate) (PVAc) and poly(methyl acrylate) (PM(A)), in the same solvent testifies that the previously published relations remain valid for T T g . They enable the determination of viscosities of the pure polymers below…
Synthesis of polyvinyl acetate-graft-poly-2-oxazolines
1994
Poly(vinyl acetate-co-vinyl chloroformate) (1) was synthesized via phosgenation of poly(vinyl acetate-co-vinyl alcohol). It was shown that (1) is capable of initiating the polymerization of 2-phenyl-2-oxazoline and 2-methyl-2-oxazoline, when the counter ion is exchanged using potassium iodide. Polyvinyl acetate-graft-poly-2-phenyl-2-oxazoline and polyvinyl acetate-graft-poly-2-methyl-2-oxazoline are obtained in the grafting reaction.
MCM-41 and related materials as media for controlled polymerization processes
1994
The synthesis of mesoporous MCM-41 type materials based on transition metal oxides and the polymerization of several monomers within MCM-41 is presented with the aim to specifically investigate the effects of the interface and confinement on host-guest interactions. In addition to standard MCM-41, material based on transition metal oxides is obtained although template removal has been unsuccessful for such compounds until now. In situ polymerization of styrene, methyl methacrylate and vinyl acetate is possible within the mesopore system. The properties of some of the encapsulated polymers differ markedly with those obtained in the bulk.
The structure of gas-filled n-butyl-2-cyanoacrylate (BCA) polymer particles
1995
Abstract The structure of gas-filled poly-[n-butyl-2-cyanoacrylate] (BCA) particles has been demonstrated by negative staining with uranyl acetate, platinum-carbon shadowing of air-dried material and thin sectioning of the aqueous suspension of BCA particles, embedded in water-soluble melamine resin. The polymer shell of the hollow particles possesses a globular outer surface and a smoother inner surface.
Formation of micro- and nano-spheric particles (filter dust) during the preparation of cellulose acetate membranes
2003
Abstract Membranes were prepared from six samples of cellulose acetate (CA) differing in their average molecular weight (75–260 kg/mole) and molecular weight distribution using methyl acetate as solvent and 2-propanole as precipitant. The routes through the phase diagram and the evaporation times were varied in these experiments. Electron microscopy demonstrates that the amount of filter dust (CA particles deposited on the membrane surface) decreases as the fraction of low molecular weight material in the starting polymer becomes less. For low average molar mass of CA and moderate polymer concentrations in the casting solution the dust consists of individual spheres of relatively uniform si…
Enhancing the mechanical performance of polymer based nanocomposites by plasma-modification of nanoparticles
2012
Abstract The possibility of enhancing the mechanical performance of two different polymer-based nanocomposites using polyamide 6 (PA6) and poly[ethylene-co-(vinyl acetate)] (EVA) as matrices was investigated. The nanofillers used were, respectively, either carbon nanotubes (CNTs) or an organically modified montmorillonite (Cloisite 15A), both previously modified by plasma treatment to introduce polar moieties. The nanofillers were fully characterized by Raman spectroscopy, XPS, FT-IR and XRD, demonstrating their effective modification with oxygenated groups. The nanocomposites were prepared by melt processing in order to obtain films and fibres. The mechanical tests carried out on the nanoc…