Topic
Vinyl acetate
About: Vinyl acetate is a research topic. Over the lifetime, 15970 publications have been published within this topic receiving 162142 citations. The topic is also known as: Ethenyl acetate & Ethenyl ethanoate.
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TL;DR: (R)- and (S)-2-(Acetyloxy)-propanal were used as the starting materials in the synthesis of chiral isoxazoline and imidazole derivatives which proceeded without racemization of the chiral center.
63 citations
TL;DR: In this paper, a theoretical investigation of the emulsion polymerization of vinyl acetate in a continuous stirred tank reactor operating under conditions of sustained oscillations is reported, and models of two levels of sophistication are developed: a comprehensive model that solves for the age distribution function of polymer particles and a simplified model that assumes discrete nucleation periods.
Abstract: A theoretical investigation of the emulsion polymerization of vinyl acetate in a continuous stirred tank reactor operating under conditions of sustained oscillations is reported here. Models of two levels of sophistication are developed: a comprehensive model that solves for the age distribution function of polymer particles and a simplified model that assumes discrete nucleation periods. The latter model should find use in adaptive control of latex reactors. These models adequately simulate experimental data after Greene et al.2 for the emulsion polymerization of vinyl acetate under conditions of sustained oscillations.
63 citations
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.
63 citations
TL;DR: In this paper, a series of LDPE blends with plasticized (PLST) and granular starch (FILST) were prepared, and the second derivative IR spectra showed peak shifts similar to those observed in V-type starch complexes with ethylene/vinyl alcohol copolymers.
Abstract: A series of LDPE blends with plasticized (PLST) and granular starch (FILST) were prepared. Ethylene/vinyl acetate (EVA) copolymer was used as a compatibilizer in three different amounts: 10, 25 and 50 wt% based on starch. The blends were studied by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Second derivative IR spectra showed peak shifts similar to those observed in V-type starch complexes with ethylene/vinyl alcohol copolymers. The possibility for V-type complex formation is supported by the lower biodegradation rates of the blends containing higher amounts of EVA. Mechanical properties of the blends, especially elongation at break, were satisfactory even for blends containing high amounts of starch (20–30 wt%).
63 citations
TL;DR: In this article, the effect of viscosity ratio for melts of the components on the processes of fiber formation in extrudates and on the rheological properties of the molten blend has been tested.
Abstract: Blends of polyoxymethylene (POM) with a copolymer of ethylene and vinyl acetate (CEVAc) have been studied. The effect of viscosity ratio for melts of the components on the processes of fiber formation in extrudates and on the rheological properties of the molten blend has been tested. The viscosity ratio of the fiber-forming POM and the matrix varied in the range 0.35-27.7. POM ultrathin fibers of unlimited length can be formed in the CEVAc only at a viscosity ratio close to unity. For ratios much greater than unity, the extrudate is found to contain short fibers and a finely dispersed powder or no fibers at all. If the viscosity of the POM melt is lower than that of the matrix, films are formed in addition to fibers. The second factor that governs fiber formation is the extrusion shear stress. An optimum shear stress exists at which the amount of ultrathin fibers is a maximum.
63 citations