Vinyl acetate

The polymer electrolytes comprising blend of poly(vinyl acetate) (PVAc) and poly(methylmethacrylate) (PMMA) as a host polymer and LiClO4 as a dopant are prepared by solution casting technique. The amorphous nature of the polymer–salt complex has been confirmed by XRD analysis. The DSC thermograms show two Tg's for PVAc–PMMA blend. A decrease in Tg with the LiClO4 content reveals the increase of segmental motion. Conductance spectra results are found to obey the Jonscher's power law and the maximum dc conductivity value is found to be 1.76 × 10− 3 S cm− 1 at 303 K for the blend polymer complex with 20 wt.% LiClO4, which is suitable for the Li rechargeable batteries. The conductivity–temperature plots are found to follow an Arrhenius nature. The dc conductivity is found to increase with increase of salt concentration in the blend polymer complexes.

A polyhedral oligomeric silsesquioxane (POSS) tethered imidazolium surfactant was used to exchange montmorillonite for the preparation of polymer nanocomposites in polystyrene, poly(ethylene-co-vinyl acetate), and polyamide-6 using a melt blending technique. Simultaneous temperature resolved small angle X-ray scattering and wide angle X-ray diffraction was used to monitor the surfactant stability and phase behavior of the polyamide-6 nanocomposites. Good thermal stability of the surfactant was in agreement with thermogravimetric analysis. Transmission electron microscopy revealed a mixed intercalated/exfoliated structure, with the presence of small tactoids exhibiting gallery spacings greater than 3.8 nm in all three polymers. Fluorescently tagged organically exchanged montomorillonite was used to assess the quality of nanoparticle dispersion. Exchanging the montmorillonite with lower loadings of the POSS surfactant slightly increased the size of clay tactoids, but did not significantly alter the gallery spacing or overall dispersion. The results suggest that the bulky and rigid structure of POSS, as well as its tendency to aggregate into ordered crystals, form a bilayer structure in the clay galleries and prevent montmorillonite from completely exfoliating, even in polyamide-6.

Racemic cis- and trans-1-aminoindane-2-carboxylic acids (3 and 5) were prepared from indene by chlorosulphonyl isocyanate addition followed by ring opening and isomerisation. The intermediate racemic hydroxymethylated β-lactam 6 was resolved through the lipase-catalysed asymmetric acylation of the primary hydroxy group at the (R)-stereogenic centre. High enantioselectivities (E>200) were observed when the enzymatic reactions were performed with lipase AK or lipase PS as catalyst and vinyl acetate or vinyl butyrate as acyl donor. The hydrolysis and isomerisation resulted in all four enantiomers (9, 11, 13 and 14) of 1-aminoindane-2-carboxylic acid, a new benzologue of cispentacin.

Background: Use of enzymes in low water media is now widely used for synthesis and kinetic resolution of organic compounds. The frequently used enzyme form is the freeze-dried powders. It has been shown earlier that removal of water molecules from enzyme by rinsing with n-propanol gives preparation (PREP) which show higher activity in low water media. The present work evaluates PREP of the lipase (from Rhizomucor miehei) for kinetic resolution of (R,S)-β-citronellol. The acylating agent was vinyl acetate and the reaction was carried out in solvent free media.

The elimination or minimization of non-specific protein adsorption from serum is critical for the use of surface plasmon resonance (SPR) sensors for in vitro and in vivo analysis of complex biological solutions. The ultimate goals in this application are to minimize non-specific adsorption of protein and to maximize analyte signal. A reduction of the non-specific protein adsorption from serum of

A new Micrococcus luteus strain BST20 was isolated with ability to metabolize PAN polymers as sole carbon source. Out of seven synthetized PAN copolymers containing different moieties of acrylic acid and/or vinyl acetate the polymer with lowest crystallinity (PAN with 5% vinyl acetate) was most easily metabolized. 13 C labelled PAN was completely converted to the acrylic acid by this strain. M. luteus BST20 produced membrane-bound nitrile hydrolysing enzymes able to convert nitrile groups on PAN powder surface to the corresponding acids. Similarly, nitrile groups on PAN fabrics were transformed to the corresponding acid as indicated by an K/S increased after dying with Methylene blue and the released ammonia. On small soluble substrates the enzyme system showed a preference for aliphatic and aromatic substituted aliphatic nitriles.

The true monomer reactivity ratios for the vinyl acetate/butyl acrylate system were determined with experimental data from the cumulative copolymer composition at low, intermediate, and high conversions and with the monomer partitioning among the aqueous, microemulsion droplet, and polymer particle phases taken into account. A mixture of sodium dodecyl sulfate and poly(ethylene oxide) (23) dodecyl ether (Brij-35; 3 : 1 w/w) was used as a stabilizer. Potassium persulfate was used as an initiator. The true values of the monomer reactivity ratios were 0.028 AE 3.2 Â 10 À3 for vinyl acetate and 6.219 AE 3.1 Â 10 À1 for butyl acrylate, and these were

Both peracetyl α-glucosamine 3 and its β-epimer 4 undergo alcoholysis with butanol in THF, catalysed by lipase from Candida antarctica (Novozym 435) to afford the triester 6 and diester 9, respectively. Esterification of these compounds, using vinyl acetate in the presence of Novozym 435, gives the partial esters 10 and 11, bearing a deprotected hydroxyl function at C-4, ready for inversion of configuration to open a route in the preparation of galactosamine.

This work presents a study of superficial properties of polyacrylonitrile (PAN) films obtained by extrusion process. This innovative material was submitted to microwave plasma treatment generated at low pressure. The contact angle was measured with and without treatment in nitrogen and argon plasma, by the pendant drop technique. The work of adhesion was calculated by the Young–Dupré equation. The surface

Batch emulsion copolymerization of vinyl acetate and 2-ethyl hexyl acrylate (VAc/2EHA = 90 : 10) was initiated by the thermal initiators ammonium persulfate and potassium persulfate at 70°C in the presence of nonylphenol ethoxylates with varying chain lengths and poly(vinyl alcohol). VAc–2EHA copolymer latexes were synthesized as two different series in a loop reactor. The first series was initiated by ammonium persulfate, and the second series was initiated by potassium persulfate. The influence of the counterions or initiators and chain lengths of a nonionic emulsifier on the properties of VAc–2EHA copolymer latexes were determined by measuring the viscosities, weight-average molecular weights, number-average molecular weights, molecular weight distribution, and surface tension of latexes to air. The results for the copolymer latexes indicated that some of their physicochemical properties increased with increasing chain length of the nonionic emulsifier, but some of them followed a different trend for the two initiators. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1380–1384, 2005

Ahxtsrmcr -The effect of ethanol vapour and temperature was investigatcd on gas sensors fabricated from poly(viny1 acetate)\carbon black composites based around a predetermined percolation threshold. Samples with 8% carbon black loading displayed the best response to the ethanol vapour. Typical response and recovery times of 140s and 45s respectively were recorded. In addition, bridge structures were fabricated, where all four resistive elements were prepared from the same composite material and in which a novel passivation process was employed. It was observed that these bridge stmchres were significantly less affected by variations in temperature in comparison to the single sensor structures.

Continuous-flow mode enantiomer selective acetylations of racemic 1-phenylethanol, 1-cyclohexylethanol, and 1-phenylpropan-2-ol (rac-1a-c, respectively) with vinyl acetate were performed in small stainless steel packed-bed reactors filled with different commercial lipase preparations. In several lipase-filled columns, highly enantiomer selective (E > 100) kinetic resolutions of these alcohols were achieved. In most cases, comparison of the continuous-flow and batch mode (shake flask) biotransformations indicated similar enantiomer selectivities (E) but higher productivities (specific reaction rate: r) in the corresponding continuous-flow reaction. The effect of temperature (0-60°C) and pressure (1-120 bar) on the continuous-flow acetylation of racemic 1-phenylpropan-2-ol was investigated in an immobilized Candida antarctica lipase B (CaLB) filled reactor. Pressure had no significant effect on r and E. Expectedly, a monotonous increase of specific reaction rate (r) was observed within this temperature range. Most surprisingly, the enantiomer selectivity had a maximum (E $ 25, at 20°C) and a minimum (E $ 7, at 50°C). The continuous-flow reactions in CaLB-filled columns were successfully applied for preparative scale kinetic resolutions of rac-1a-c.

A Purser furnace has been used to investigate the combustion toxicity of ethylene-vinyl acetate copolymer (EVA) with and without fire retardants, under different fire conditions. Steady state flaming combustion has been studied at equivalence ratios varying from 0.5 to 1.5 by driving the materials through the furnace at 750 C. Yields of CO and CO 2 for EVA containing 27% vinyl acetate, and its fire retarded composites, containing fire retardant fillers are presented. The materials contained 30% EVA and 70% hydrated aluminium oxide (ATH), or 65% ATH and 5% zinc hydroxystannate (ZS), or 5% magnesium borate (MgB) or 5% zinc borate (ZB). In each case the same mass of EVA was used in the determination. The yields of CO per g of polymer from the EVA-fire retardant composite samples showed very similar yields of CO under well ventilated conditions to the pure EVA, but generally higher CO yields than the base polymer under the most toxic fuel rich conditions. The exception to this was the sample containing ATH and zinc borate, which did not take up all the available oxygen under fuel rich conditions, and gave a much lower CO yield, corresponding to an eight-fold reduction in the combustion toxicity. Under fuel rich conditions for EVA, 60% of the carbon was lost as volatile organic species other than CO and CO 2 . For the sample containing zinc borate, this was 50% and for the remaining samples it varied from 20 to 38%. Evidence is presented which indicates that organic material trapped in the solid alumina residue is oxidised to CO, except in the presence of zinc borate, when it appears to be lost as organic carbon. #

Copolymers of vinyl acetate and ethylene were prepared by emulsion polymerization using ammonium persulphate and sodium metabisulphite as initiators in presence of cyclohexane. Several copolymer samples were prepared by changing initial pressure of ethylene from 100 to 250 psi. The copolymer composition was determined by 1H-NMR and thermogravimetric analysis in nitrogen atmosphere.

EVA (poly(ethylene-co-vinyl acetate)) redispersable powders with different contents of copolymers were tested in order to evaluate their effects on the complex interactions developed at mortar/tile interface. EVA addition has increased the bond strength almost 40% when compared with unmodified mortar. Based on EVA hydrolysis, a novel method named as 'Extension of Hydrolysis (EH)' was suggested to monitor the reaction mechanism which occurred during the interface layer formation. Thus, higher EH values were related to a significant improvement of adhesion at interface observed as a changing on the failure mode from mostly cohesion to adhesion. Calculated EH parameter of 2.64 was associated with a cohesive component of rupture in the mortar of 50% while for an EH of 0.92, the rupture in the mortar was only 7%. The enhancement on adhesion was attributed to the hybrid ceramic-polymer interface formed based on hydrogen-bonds between silanol groups from tile surface and hydroxyl groups from hydrolyzed EVA.

catalyst, water with one or more monomers, which are not miscible with water and an oil in-water emulsifier. These emulsions are generally opaque, milky, and viscous solution, but they can also be translucent emulsions with particle sizes ranging

Poly(vinyl alcohol) is often used in vinyl acetate emulsion polymerization as a protective colloid, but its role is complex and controversial since it partakes in grafting reactions with the monomer, influencing process mechanisms, and affecting the colloidal properties of the latex. Furthermore, in industrial operations, the wide scatter of macromolecular properties of the commercial types of poly(vinyl alcohol) causes process irreproducibilities. In this work different types of polyvinyl alcohol were used to perform a series of polymerizations, and their kinetics were compared. A selective solubilization procedure was applied to separate the three fractions of poly(vinyl alcohol) in the final latex: free in the water phase, physically adsorbed onto the polymer particles and chemically grafted. These results were compared with those obtained from pure adsorption measurements of polyvinyl alcohol onto 'emulsifier-free' polyvinyl acetate dispersions. The rheological behavior of the different latexes was also compared, and the results were used to formulate an hypothesis on the interaction mechanisms acting in these systems. q

2-Substituted propanediols monoacetates, derived from enzymatic asymmetrization of the corresponding diols, have been obtained in high yields and enantiomeric excesses by using lipases and vinyl acetate as both solvent and acylating agent. These chiral building blocks have been transformed into the advanced intermediate 3, useful for the enantioselective synthesis of tacamane alkaloids.

The most significant results concerning a chemical study to evaluate the degradability of polymeric components in four contemporary works of art, partially or completely realized in plastics, are presented and discussed in this paper. The procedure applied is mainly based on the use of Fourier transform IR and UV-vis spectroscopies and pyrolysis-gas chromatography/mass spectrometry, and consists of the following steps: (1) compositional analysis of the artworks, with particular attention to components which may have a negative effect on the overall ageing; (2) evaluation of the actual state of conservation; (3) investigation of the accelerated ageing of reference polymer samples; and (4) monitoring of the natural ageing of the artworks. On such a basis, the following could be concluded. Stage Evidence by Loris Cecchini is made of poly(ether urethane) elastomer which contains a high amount of phthalates. Their exudation gives a sticky appearance to the artwork and their removal during ageing is the main cause of the loss of flexibility. The latex used by Andrés Pinal for tailoring Traxe de Home is a natural polyisoprene, whose oxidative degradation accounts for the extensive deterioration and yellowing of the artwork. The plaster sculptures of 3D Bodyscans 1:9 by Karin Sander are coated with an aliphatic epoxy resin. Its oxidation with formation of amides is the cause of the surface yellowing. The adhesive used by Dario Villalba for Tierra, Ladrillo y Agua is a commercial poly(vinyl acetate). Simulated photoageing suggests a fast deterioration due to deacetylation and cross-linking, which possibly is the main reason for the actual detachment of debris from the support.

Asphalt binder was modified by low density polyethylene (LDPE) and ethyl vinyl acetate (EVA) polymers to investigate the structure-property relationships of polymer modified asphalt (PMA). The PMA was prepared in a high shear blender at 160 o C. The optimum blending time (OBT) for each polymer was determined following a separate investigation. OBT was influenced by Mw, MWD, and polymer structure. The influence of Mw of LDPE and vinyl acetate (VA) content of EVA on PMAs was studied by rheological tools. Polymer modification improved the rheological properties of base asphalt. EVA PMAs were found to be less temperature sensitive than LDPE modified asphalts. LDPE modification increased flow activation energy (E a ) but EVA modification decreased E a . Both VA content and Mw of LDPE have influenced the storage stability of PMAs. The low temperature properties of PMAs and short ageing tests were not influenced by polymer type. On the other hand, the high temperature properties of PMAs were strongly influenced by Mw of LDPE and VA content of EVA. Overall, EVA with low VA content showed the best temperature resistance to high temperature deformations, the highest upper service temperature as well as the best storage stability.

Some acetone-carried consolidants for waterlogged archaeological wood were tested in order to evaluate treatments able to save time and energy. In details, colophony (rosin), two esterified colophonies (Rosin 100 Ò and Rosin 459 Ò ), a mixture of colophony with PEG 3400 and a vinyl acetate -vinyl versate copolymer (Vinavil 8020S Ò ) were tested. The treatments were carried out at temperatures of 20 and 35 C on waterlogged maritime pine, elm, oak and beech. The materials came from the archaeological site of the ancient ships of Pisa (Tuscany, Italy) and were dated back to VII cent. BC e II cent. AD. To evaluate the processes, equilibrium moisture content and dimensional stability of treated wood samples at different relative humidity, and retention of impregnating products were measured; moreover macroscopic and microscopic examination were also run to respectively assess the shape and appearance of treated wood and the way of deposition of consolidants. The results highlighted that natural and modified colophony treatments gave the most satisfactory results both in the maintenance of shape and dimensions of samples and in the stabilization with respect to RH variations. Moreover, the equilibrium moisture contents of samples treated with R100 and R459 were much reduced in comparison to the other consolidants and to untreated archaeological wood. This fact was related to the high retention values of those products that occluded most of the porosity including the microporosity of cell walls. Therefore, in terms of higroscopicity treated wood was more similar to impregnating substances rather than to decayed wood. This fact was considered helpful in contrasting the moisture-related negative effects in cases of eventual faults in the climate control during e.g. exhibition and in protecting treated wood from the risks of new fungal attacks.

Poly(vinyl acetate-co-butyl acrylate) latexes having oligomeric N-methylol acrylamide were prepared by semi-continuous emulsion polymerization. The effects of new protective colloid and comonomer ratios on the physicochemical and colloidal properties of latexes were investigated. The changes in homopolymer and copolymer latexes were determined by measuring viscosity, particle size, molecular weight (MW), molecular weight distribution (MWD), and surface tension. \( \bar{M}_{n} \) values of copolymer latexes were found to be lower than the MWs of the poly(vinyl acetate) and poly(butyl acrylate) homopolymers. In general, \( \bar{M}_{n} \) and \( \bar{M}_{\text{w}} \) values of copolymer latexes changed irregularly with increasing BuA ratio in the copolymer composition.

The aim of the current research project was to explore the possibilities of combining pressurized carbon dioxide with hot melt extrusion of polyvinylpyrrolidone-co-vinyl acetate 64, Eudragit ® E100 and ethylcellulose 20 cps, to evaluate the ability of the pressurized gas to act as a temporary plasticizer as well as to produce a foamed polymeric material. Pressurized carbon dioxide was injected into a Leistritz Micro 18 intermeshing co-rotating twin-screw melt extruder using an ISCO 260D syringe pump. The physicochemical characteristics of the polymers before and after injection of carbon dioxide were evaluated using MDSC, dissolution measurements, specific surface area measurements, porosity, dynamic vapour sorption and microscopy. An extruder set up and screw configuration were configured and optimized for injection of pressurized CO 2 . Carbon dioxide acted as plasticizer for all three polymers, reducing the processing temperature during the hot melt extrusion process. The specific surface area and the porosity of the polymers was increased after treatment with carbon dioxide, resulting in enhanced dissolution. The macroscopic morphology was changed to a foam-like structure due to expansion of the carbon dioxide at the extrusion die. This resulted in improved milling efficiency.

In order to fulfill a need to measure water in crude oils containing materials that interfere with the measurement of water by the Karl Fischer method, by reacting with iodine or iodide, a coulometric method has been developed and validated using 0.1 mol L -1 Sodium thiosulfate as a calibrant. These interfering substances were measured in water-mass-equivalents, which were expressed as the mass of water that reacts with an equal mass of iodine in the Karl Fischer method. The SO 2 -free reagent that has been modified reacts quantitatively with sodium thiosulfate, cysteine and ascorbic acid but does not react with vinyl acetate. The level of interfering substances was measured in five transformer oils (including Reference Materials RM 8506 and RM 8507), a high and a low sulfur crude oil (Standard Reference Materials SRM 2721 and SRM 2722 respectively), a white oil, a high-vacuum oil and a high-viscosity base-stock oil. One oil contained less than 10 mg kg -1 (water-mass-equivalents of interfering substances in oil) and two oils (RM 8507 and Drakeol 35) contained no measurable amount of interfering material (<0.2 mg kg -1 ). SRM 2271, a sour crude oil contained 834 mg kg -1 (standard deviation (SD)=25 mg kg -1 ) (water-mass-equivalents of interfering substances in oil). Approximately 20% of this material was volatile and an additional 20% appeared to undergo some degradation (possibly oxidation) once the oil was exposed to air. These results indicate that this is a general method for measuring substances in oils that react with iodine and that it is capable of measuring in a variety of oils, using commercial instrumentation, interfering substances that inflate water measurements.

Dispersion of liquid-liquid systems is commonly applied in industrial processes such as extraction, suspension, and emulsion polymerization. This article describes the influence of the quality of emulsification on the course and outcome of a batch-emulsion polymerization of styrene and vinyl acetate. From visualization experiments and polymerizations in combination with reaction calorimetric studies, a critical impeller speed, N*, can accurately be determined for a particular reactor setup and a given recipe. The results show that styrene-water emulsions are more difficult to emulsify than vinyl acetate-water emulsions. In general, a large turbine impeller appears to be more effective in emulsifying monomer-water dispersions than a pitchedblade impeller. In addition, for vinyl acetate emulsion polymerization, the possibility of premixing the reaction mixture has been investigated.

The physical properties of a highly syndiotactic poly(vinyl alcohol) (PVA, diad syndiotacticity r 69% and a commercial, atactic PVA r 54% were examined. The highly syndiotactic PVA was derived from poly (vinyl acetate) prepared through the radical polymerization of vinyl acetate in (CF 3 ) 2 CHOH. The solubility, gelation behavior, melting point, and crystallization rate were drastically affected by the tacticity of the main chain. Some of the properties were measured using ®ber samples prepared by the gel spinning technique. The ®ber obtained from the syndiotactic PVA had a melting point of 2748C. This is the highest melting point reported for PVA. These effects of tacticity on the polymer properties are ascribed to the difference in intermolecular and/or intramolecular hydrogen bonding. A polymer chain with higher r content may form more regular and therefore more rigid hydrogen bonding between the polymer chains in the bulk sample. Such a detailed study on the effects of tacticity on the properties of PVA has not been reported so far. q

This work performs the dynamic optimization of semibatch vinyl acetate (VAc)/acrylic acid (AA) suspension copolymerizations. The proposed dynamic optimization strategy is based on a direct search Complex algorithm and is used to control the copolymer composition along the batch. First, a sequential optimization procedure is used to determine the optimum AA concentration and feed rate profiles, required to provide the specified copolymer composition. In the second step, a sequential optimization procedure is coupled with a predictive controller to guarantee that the manipulation of feed flow rates can allow for attainment of the desired copolymer compositions. The optimization strategy is validated through simulation, by assuming that reactions are subject to perturbations of the reaction temperature, initiator, and VAc concentrations. It is shown that the proposed optimization strategy can be used successfully both for design of monomer feed rate profiles and removal of process disturbances during semibatch suspension copolymerizations, to keep the copolymer composition constant throughout the batch. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Free radical copolymerization reaction of vinyl acetate (VA) and methyl acrylate (MA) in solution of benzene-d 6 using benzoyl peroxide (BPO) as the initiator was studied with on-line 1 H NMR kinetic experiments at 60 C. It was observed that composition drifts in the comonomer mixture with reaction progress is significant. Hence, the monomer reactivity ratios of VA/MA system could be calculated by the data collected only from one sample via on-line following the comonomer mixture and copolymer compositions at different reaction time intervals up to medium overall monomer conversions. The results were in good agreement with the literature data reported for this system. The good fitting between theoretical and experimental changes in the comonomer mixture compositions as a function of reaction progress was observed, indicating the accuracy of the monomer reactivity ratios calculated by the new procedure presented here.

The formation of volatile organic compounds through secondary reactions during the post-polymerization of vinyl acetate containing latexes using organic hydroperoxides with ascorbic acid as redox initiator was investigated. It was found that such initiator systems are highly effective in reducing free vinyl acetate but organic by-products are produced. A reaction scheme consistent with the kinetic data is presented. ᭧

In recent times, polymer-layered silicate nanocomposites have drawn a great deal of attention because they often exhibit tremendous improvements in material properties compared with virgin polymers or conventional microor macro-composites. In the present study, nanocomposites were developed from organically modified clay and poly(ethylene-co-vinyl acetate-co-carbon monoxide) by melt mixing. FTIR spectroscopy reveals that the interaction between the organoclay and EVACO is thermodynamically favored. High resolution wide angle X-ray diffraction and transmission electron microscopy were used to study the morphology of the nanocomposites. Elemental mapping by scanning electron microscopy indicates good dispersion and distribution of the nanoclay in EVACO matrix. The mechanical properties of the nanocomposites are optimum at a clay loading of 3%.

ABSTRACT: The role of grafting in particle nucleation during the emulsion polymerization of vinyl acetate with partially hydrolyzed poly(vinyl alcohol) (PVA) as an emulsifier and potassium persulfate as an initiator was investigated. The polymerizations were carried out in batch with a low solids (10%) recipe. An automated reaction calorimeter (Mettler RC1) was used for the direct monitoring of the kinetics of emulsion polymerizations with three medium molecular weight PVAs differing in their degrees of blockiness (Poval 217EE. 217E. 217). Smith–Ewart case 1 kinetics (average number of free radicals per particle, 0.5) were followed in all cases, and no constant rate in interval II was observed. Contrary to what was expected, a nonlinear relationship was observed between the rate of polymer-ization (Rp) and the number of particles (Np). At Rp max, Np (217E). Np (217EE). Np (217), and the final Np was independent of the degree of blockiness of PVA. The particle size distributions were...

The gas separation properties of ethylene vinyl acetate (EVA) membranes containing 18 and 28 wt% of vinyl acetate (VA) were investigated in this study. The effects of membrane preparation conditions, such as thermal and thermal/wet phase inversion, and the type of solvent on the gas separation properties of EVA membranes were investigated. The permeation of pure O 2 , N 2 , CH 4 , and CO 2 gases at different feed pressures ranging from 2 to 11 bar were examined.

O poli[(etileno)-co-(acetato de vinila)] (EVA) possui grande aplicação na indústria calçadista, sendo utilizado na confecção de placas expandidas para posterior corte de palmilhas e entressolas. Estudos realizados na região sul do Brasil mostraram que os resíduos gerados pela indústria calçadista foram superiores a 200 toneladas/mês em 2001, sendo o maior volume oriundo de recortes de placas expandidas. Por isso, o objetivo deste trabalho foi o de caracterizar resíduos de EVA de chapas expandidas, visando à reciclagem mecânica desse material. Análises em MEV demonstraram que o resíduo de EVA apresenta uma morfologia microcelular que é destruída após o processo de moagem. O resíduo de EVA moído apresenta duas fases, uma reticulada (matriz) e uma não-reticulada (dispersa). O resíduo de EVA apresentou teor de gel de aproximadamente 75% em massa, cerca de 20% em massa de acetato de vinila (VAc), fora processado a partir de EVA com aproximadamente 28% de VAc e possui teor de carga inorgâ...

In the present work, experimental density measurements are reported along with the derived thermodynamic properties, such as the isothermal compressibility (κ T ), the isobaric expansivity (R p ), and the thermal pressure coefficient (γ V ) for imidazolium-, pyridinium-, pyrrolidinium-, and piperidinium-based ionic liquids (ILs), namely, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [C 2 mim][CF 3 SO 3 ], 3-methyl-1-propylpyridinium bis(trifluoromethylsulfonyl)imide [C 3 mpy][NTf 2 ], 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide [C 3 mpyr][NTf 2 ], 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [C 4 mpyr][NTf 2 ], and 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide [C 3 mpip][NTf 2 ] in the pressure (0.10 < P/MPa < 35.00) and temperature (293.15 < T/K < 393.15) domains. These ILs were chosen to provide an understanding of the influence of the cation and anion on the properties under study. Experimental densities are correlated with the Tait equation with an average absolute relative deviation (AARD) better than 0.02 %. It is shown that experimental densities are in good agreement with the densities obtained by the predictive method previously proposed by us.

An efficient asymmetric synthesis of 1,4-dihydropyridine derivatives is described. The key step is the stereoselective Michael addition using t-butyl ester of L-valine as a chiral auxiliary to achieve good ee (>95% for all the tested experiments) and moderate yield. With this method, (+)-4-(3-chlorophenyl)-6dimethoxymethyl-2-methyl-1,4-dihydropyridine-3,5-dicarboxylic acid cinnamyl ester was obtained and was characterized as a promising N-type calcium channel blocker with improved selectivity over L-type compared to its (À)-and racemic isomers.

Racemates of cis-and trans-2-(N β -t-butoxycarbonyl-N α -methylhydrazino)cyclopentanols and -cyclohexanols 1-4 were resolved through lipase PS-or Novozym 435-catalysed asymmetric acylation of the secondary OH group at the (R)-stereogenic centre. High enantioselectivity (E >200) was observed when vinyl acetate or vinyl butyrate was used in diisopropyl ether, resulting in the enantiopure hydrazino esters 1a-4a and hydrazino alcohols 1b-4b. Methanolysis of the esters 1a-4a afforded the corresponding 2-hydrazinocycloalkanols 1c-4c (ee usually >95%).

Elastic moduli of poly(vinyl acetate) networks swollen in toluene and acetone (good solvents) and in isopropyl alcohol (theta solvent) were studied. The influences of crosslinking density and activity of diluent, as well as the interactions between polymer and swelling agent, were investigated. To describe these three different effects, a phenomenological equation was proposed and checked by experiments.

Conducting blends of ethylene-vinyl acetate (EVA) copolymers with different vinyl acetate content and polyaniline doped with dodecylbenzenesulfonic acid (Pani-DBSA) prepared by three different procedures were prepared by solution-cast process. Blend films with EVA18 (with 18 wt.% of VA) presented gross-phase separation, resulting in a formation of Pani-enriched (glass-contacted film surface) and Pani-deficient (air-exposed film surface) layers. The use of EVA41 (with 41 wt.% of VA) resulted in blends with homogeneous conductivity (similar conductivity in both sides of the film). Better electrical performance was achieved in blends with Pani-DBSA produced by a redoping process. Concerning Pani-DBSA prepared by one-step polymerization, one prepared by inverted emulsion polymerization, resulted in EVA41-based blends with lower percolation threshold point and a more homogeneous morphology than that prepared with Pani-DBSA from aqueous dispersion polymerization. #

Polyindole dispersions consisting of 20–30-nm-sized nanoparticles are prepared by chemical oxidation with ferric chloride using sodium dodecyl sulphate, poly(vinyl alcohol) and poly(vinyl acetate) as steric stabilizers. Pure acetonitrile and acetonitrile–water mixtures are used as solvents. The particle size depended on the concentrations of monomer and the steric stabilizer. The dispersions are characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform IR spectroscopy, thermal analysis and cyclic voltammetry techniques.

Poly(vinyl acetate-co-butyl acrylate) latexes having oligomeric N-methylol acrylamide were prepared by semi-continuous emulsion polymerization. The effects of new protective colloid and comonomer ratios on the physicochemical and colloidal properties of latexes were investigated. The changes in homopolymer and copolymer latexes were determined by measuring viscosity, particle size, molecular weight (MW), molecular weight distribution (MWD), and surface tension. \( \bar{M}_{n} \) values of copolymer latexes were found to be lower than the MWs of the poly(vinyl acetate) and poly(butyl acrylate) homopolymers. In general, \( \bar{M}_{n} \) and \( \bar{M}_{\text{w}} \) values of copolymer latexes changed irregularly with increasing BuA ratio in the copolymer composition.

The effect of vehicle ethanol concentration and membrane vinyl acetate (VA) content on the diffusion properties of poly (ethylene-vinyl acetate) (EVA) membranes was studied. The maximum flux of a model drug, benzocaine, through EVA membranes increases with increasing ethanol concentration and membrane VA content. The flux enhancement is attributed to the increases of both benzocaine membrane solubility and diffusivity. For any given ethanol concentration, increasing membrane VA content increases both solubility and diffusivity of benzocaine due to the amorphous nature of VA, which contributes to higher polymer chain mobility. For the membrane with a given VA content, increasing ethanol concentration results in the increased diffusivity due to membrane swelling by ethanol. The effect of ethanol concentration on benzocaine membrane solubility appears to be much less than the effect on the diffusivity. The relationship between diffusivity and membrane swelling is in excellent agreement with the general free volume theory.

Crystalline structures, nonisothermal crystallization behavior and surface folding free energy of polypropylene (PP)/poly(ethylene-co-vinyl acetate) (EVA) blend-based organically modified montmorillonite (OMMT) nanocomposites were investigated by use of wide angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) techniques. Nonisothermal crystallization kinetic analysis was performed using Avrami equation modified by Jeziorny as well as combined Avrami-Ozawa method. Surface folding free energy and

Stable monodisperse poly(vinyl acetate) (PVAc) submicronic latex particles were synthesized by ab initio batch emulsion polymerization using a dextran derivative from renewable resource as an efficient steric stabilizer. The dextran end-functionalized by a xanthate moiety was synthesized by Huisgen's 1,3-dipolar cycloaddition (click chemistry). It was applied as a macromolecular RAFT (reversible addition fragmentation chain transfer) agent in surfactant-free emulsion polymerization of vinyl acetate to form in situ an amphiphilic block copolymer able to efficiently stabilize the latex particles. The method afforded the preparation of high solids content (27%) latices coated by dextran. Both the kinetic study and the molar mass analyses confirmed the involvement of the dithiocarbonate group in the emulsion polymerization process.