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Acetone Extraction (acetone + extraction)
Selected AbstractsCharacter of long-chain branching in highly purified natural rubberJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Sureerut Amnuaypornsri Abstract The nature of long-chain branching in natural rubber (NR) from Hevea brasiliensis was analyzed for NR purified by enzymatic deproteinization in the latex state followed by acetone extraction in the solid state to remove the proteins and neutral lipids, respectively. The treatment of purified NR in a toluene solution with a polar solvent, such as methanol or acetic acid, resulted in a clear decrease in the molecular weight, gel content, and Huggins' constant; this was caused by the decomposition of branch points in the purified rubber. This finding clearly showed that long-chain branching in the purified NR was mainly derived from the association of phospholipids linked with both terminal groups in the rubber chain via hydrogen bonds. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Expansion mechanisms of plastic/wood-flour composite foams with moisture, dissolved gaseous volatiles, and undissolved gas bubbles,POLYMER ENGINEERING & SCIENCE, Issue 7 2003G. M. Rizvi The large quantity of moisture in wood-flour may lead to the deterioration of the cell structure of foamed plastic wood-flour composites in terms of cell size, non-uniformity, and poor surface quality. Since these anomalies can cause poor mechanical properties of the foamed composites, the removal of the moisture from wood-flour becomes a critical issue with respect to the improvement of these properties. The wood-flour in this experimental study was first oven-dried at different temperatures and then subjected to acetone extraction and thermogravimetric analysis (TGA). The oven-dried wood-flour was blended with plastic and then subjected to extrusion foaming. The results obtained from the TGA studies indicate that most volatiles were released from the extractives. Conversely, a comparative experimental study of the foaming behavior of these plastic/wood-flour composites versus that of undried wood-flour composites confirms that removal of the adsorbed moisture from wood-flour results in a better cell morphology. However, it seems that some gaseous emissions released from wood-flour are soluble in plastic and thereby favorably contribute to the development of the cell morphology. This paper describes the expansion mechanisms of wood-flour composite foams resulting from the adsorbed moisture and dissolved gaseous emissions as well as resulting from the finely dispersed undissolved gas bubbles released from a chemical blowing agent. [source] Plasma polymerization and deposition of glycidyl methacrylate on Si(100) surface for adhesion improvement with polyimidePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2001X. P. Zou Abstract Thin polymer films were deposited on Si(100) surfaces by plasma polymerization of glycidyl methacrylate (GMA) under different glow discharge conditions. The FT-IR, X-ray photoelectron spectroscopy (XPS), and amine treatment results suggested that the epoxide functional groups of the deposited films had been preserved to various extents, depending on the plasma deposition conditions. The use of a low radio frequency power (, 5 W) and a relatively high system pressure (100,400 Pa) readily resulted in the deposition of thin films having nearly the same composition of the epoxide functional groups as that of the GMA homopolymer. The plasma-polymerized GMA (PP-GMA) thin films deposited on the Ar plasma-pretreated Si(100) surfaces were retained to a large extent after acetone extraction, suggesting the presence of covalent bonding between the PP-GMA layer and the Si surface. Thermal imidization of the poly(amic acid) precursor of polyimide on the GMA plasma-polymerized Si(100) surface resulted in a strongly adhered polyimide film. The adhesion results further suggested that the GMA polymer had been grafted on the Si(100) surface and the epoxide functional groups had undergone reactive interaction (curing) with the carboxylic and amine groups of the poly(amic acid) during thermal imidization. Copyright © 2001 John Wiley & Sons, Ltd. [source] Analysis of tannins in seeds and skins of Shiraz grapes throughout berry developmentAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2003MARK O. DOWNEY Abstract The flavan-3-ol and proanthocyanidin composition of both seeds and skin of Vitis vinifera L. cv. Shiraz grapes was determined by reversed-phase HPLC after acetone extraction and acid-catalysis in the presence of excess phloroglucinol. Samples were taken at weekly intervals from fruit-set until commercial harvest. The main period of proanthocyanidin accumulation in grape seeds occurred immediately after fruit-set with maximum levels observed around veraison. Over two seasons there was variation in both the timing and content of proanthocyanidins in seeds. In skin, proanthocyanidin accumulation occurred from fruit set until 1,2 weeks after veraison. Proanthocyanidin subunit composition was different in seeds and skin and changed during berry development but the mean degree of polymerisation of the tannin polymers in skins was higher than in the seeds at all stages of berry development. Proanthocyanidin levels in both seeds and skin decreased between veraison and harvest. Additional proanthocyanidin subunits were released when the residues remaining after acetone extraction were subjected to direct acid-catalysis in the presence of phloroglucinol. In the seeds, these accounted for much of the post-veraison decrease, but not in grape skin. At harvest, 75% of extractable berry proanthocyanidin was in the seeds. Accumulation of proanthocyanidins in the seeds appears to be independent of that in the skins, but in both tissues synthesis occurs early in berry development and maximum levels are reached around veraison. [source] Hg2+ Reacts with Different Components of the NADPH: Protochlorophyllide Oxidoreductase MacrodomainsPLANT BIOLOGY, Issue 3 2004K. Solymosi Abstract: The molecular background of Hg2+ -induced inhibition of protochlorophyllide (Pchlide) photoreduction was investigated in homogenates of dark-grown wheat leaves. Our earlier work showed that 15 min incubation with 10 -2 M Hg2+ completely inhibits the activity of NADPH: Pchlide oxidoreductase. Detailed analysis of spectra recorded at 10 K indicated the appearance of emission bands at 638 and 650 nm, which are characteristic for NADP+ -Pchlide complexes. Fluorescence emission spectra recorded with different excitation wavelengths, fluorescence lifetime measurements and the analysis of acetone extractions revealed that Hg2+ can also react directly with Pchlide, resulting in protopheophorbide formation. At 10 -3 M Hg2+, the phototransformation was complete but the blue shift of the chlorophyllide emission band speeded up remarkably. This indicates oxidation of the NADPH molecules that have a structural role in keeping together the etioplast inner membrane components. We suggest a complex model for the Hg2+ effect: depending on concentration it can react with any components of the NADPH: Pchlide oxidoreductase macrodomains. [source] | ||||||||||