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Solvent Power (solvent + power)
Selected AbstractsSupercritical carbon dioxide extraction of sea buckthorn (Hippophae rhamnoides L.) pomaceJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2007Dániel Cossuta Abstract BACKGROUND: The goal of this work was to utilize the sea buckthorn pomace, which is the by-product of a sea buckthorn juice process. Pilot plant supercritical fluid extraction (SFE) experiments were performed in a 5 × 10,3 m3 volume high-pressure vessel. The effects of pressure and temperature on extraction yield and recoveries of biologically active components were studied using a 32 full factorial design. The pressure and temperature were varied over the ranges of 30,46 MPa and 313,353 K, respectively. The extract samples were analysed by TLC-densitometry, UV/VIS spectrofotometry and HPLC methods. RESULTS: The obtained yields changed between 142,164 g kg,1, according to the solvent power of the supercritical fluid. The recoveries of the different minor components were (g minor components kg,1 dried raw material): 2.50,4.25 sitosterol, 0.20,1.60 ursolic acid, 0.04,0.18 carotenoid, 0.35,0.42 total tocopherol. CONCLUSION: By evaluation the designed experiments 46 MPa and 333 K were chosen as the optimum conditions. Copyright © 2007 Society of Chemical Industry [source] Processability and mechanical properties of commercial PVC plastisols containing low-environmental-impact plasticizersJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 3 2009Paola Persico Preliminary results are presented concerning the use of less-toxic plasticizers such as dioctyl adipate (DOA) and acetyl tributyl citrate (ATBC) in plastisol formulations for rotational molding technology. The DOA and ATBC plasticizers have been studied by comparing the effects of their content, molecular architecture, and polarity on the rheological behavior of liquid plastic systems and on the mechanical properties of the ultimate products prepared with PVCs having different particle sizes and molecular-weight distributions. Rheological tests have confirmed the differences in solvent power of the diethylhexyl phthalate (DOP), DOA, and ATBC plasticizers. The glass transition temperatures measured on rotomolded samples have shown that the use of ATBC leads to a more nearly rigid system as a consequence of the branched structure and polarity of this plasticizer when compared with DOA. Mechanical tests carried out on final products after natural and forced environmental aging revealed a slight decrease in their performance. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers [source] Sphere-to-Rod Transition of Micelles formed by the Semicrystalline Polybutadiene- block -Poly(ethylene oxide) Block Copolymer in a Selective SolventMACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2010Adriana M. Mihut Abstract We present a morphological study of the micellization of an asymmetric semicrystalline block copolymer, poly(butadiene)- block -poly(ethylene oxide), in the selective solvent n -heptane. The molecular weights of the poly(butadiene) (PB) and poly(ethylene oxide) (PEO) blocks are 26 and 3.5,kg,·,mol,1, respectively. In this solvent, micellization into a liquid PEO-core and a corona of PB-chains takes place at room temperature. Through a thermally controlled crystallization of the PEO core at ,30,°C, spherical micelles with a crystalline PEO core and a PB corona are obtained. However, crystallization at much lower temperatures (,196,°C; liquid nitrogen) leads to the transition from spherical to rod-like micelles. With time these rod-like micelles aggregate and form long needles. Concomitantly, the degree of crystallinity of the PEO-cores of the rod-like micelles increases. The transition from a spherical to a rod-like morphology can be explained by a decrease of solvent power of the solvent n -heptane for the PB-corona chains: n -Heptane becomes a poor solvent at very low temperatures leading to a shrinking of the coronar chains. This favors the transition from spheres to a morphology with a smaller mean curvature, that is, to a cylindrical morphology. [source] Preparation and properties of poly(L -lactic acid) scaffolds by thermally induced phase separation from a ternary polymer,solvent systemPOLYMER INTERNATIONAL, Issue 12 2004Shirong Li Abstract Poly(L -lactic acid) (PLLA) foams for tissue engineering were prepared via thermally induced phase separation of a ternary system PLLA/dioxane/tetrahydrofuran (THF) followed by double solvent exchange (water and ethyl alcohol) and drying. An extension to solidification from solution of a previously developed method for solidification from the melt was adopted. The technique is based on a continuous cooling transformation (CCT) approach, consisting in recording the thermal history experienced by rapidly cooled samples and then analyzing the resulting sample morphology. Different foams were produced by changing the relative amount of dioxane and THF in the starting solution while the amount of polymer was kept constant. Results show that the final morphology and crystallinity (measured by DSC) depend on solvent power, which in its turn was determined by the ratio dioxane/THF, and a minimum of pore size, optimum final crystallinity and crystallization rate were achieved for a system containing 70 % of dioxane. Under this condition, a higher bulk density (evaluated by Hg intrusion porosimetry) and a larger specific surface area (measured by BET N2 sorption technique) was achieved. Copyright © 2004 Society of Chemical Industry [source] | ||||||||||