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Larger Specific Surface Area (larger + specific_surface_area)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Effect of Surface Modification on the Synthesis of Pore-Filling Polymeric Monoliths in Microfiltration Membranes Made from Poly(propylene) and Poly(ethylene terephthalate)

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 3 2007
Abdus Salam
Abstract The effect of pre-modification on the interaction of macroporous substrates (membranes) with mainly micro- and mesoporous polymer monoliths has been studied. Bulk, porous polymer monoliths were synthesized to optimize the synthesis conditions and their pore morphology, and the data were used as benchmark for this study. Pre-modification of the entire pore surface of PP microfiltration membranes and PET track-etched membranes by UV-initiated grafting with PEGMA was performed using well-established methods, including coating with the photo-initiator, benzophenone. Subsequently, these membranes were functionalized by filling the pores with porous polymer monoliths from MAA and EDMA and compared with membranes that had been functionalized without the pre-modification step. The materials were characterized mainly by the degree of grafting, SEM and by the gas-adsorption-isotherm method. The DG values, after composite-membrane preparation under identical conditions, were not influenced by the pre-modification. However, it could be clearly seen from the SEM images that the pre-modification step prevents the formation of voids at the monolith-membrane pore interface. Larger specific surface area and pore volume values for composite membranes, prepared after pre-modification, fully support the SEM results. Especially large differences in pore structure between the two different composite membranes were found in the mesopore range. The results of this study indicate that it is possible to prepare porous, composite membranes where the trans-membrane transport is exclusively controlled by the pore and surface structure of a functional polymeric monolith, for example, made from a molecularly-imprinted polymer. [source]

Preparation and properties of poly(L -lactic acid) scaffolds by thermally induced phase separation from a ternary polymer,solvent system

POLYMER INTERNATIONAL, Issue 12 2004
Shirong 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]

Effect of genipin-crosslinked chitin-chitosan scaffolds with hydroxyapatite modifications on the cultivation of bovine knee chondrocytes

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2006
Yung-Chih Kuo
Abstract Chitin and chitosan were hybridized in various weight percentages by genipin crosslinkage under various prefreezing temperatures to form tissue-engineering scaffolds via lyophilization. In addition, deposition of hydroxyapatite (HA) on the surface of the porous scaffolds was performed by precipitation method to achieve modified chemical compositions for chondrocyte attachments and growths. The experimental results revealed that a lower prefreezing temperature or a higher weight percentage of chitin in the chitin-chitosan scaffolds would yield a smaller pore diameter, a greater porosity, a larger specific surface area, a higher Young's modulus, and a lower extensibility. Moreover, a higher chitin percentage could also result in a higher content of amine groups after crosslink and a lower onset temperature for the phase transition after thermal treatment. A decrease in the prefreezing temperature from ,4°C to ,80°C, an increase in the chitin percentage from 20% to 50%, and an increase in the cycle number of alternate immersion for HA deposition from 1 to 5 generated positive effects on the cell number, the content of glycosaminoglycans, and the collagen level over 28-day cultivation of bovine knee chondrocytes. © 2006 Wiley Periodicals, Inc. [source]

Adsorption Behavior of Potassium Ion on Planting Materials

CHINESE JOURNAL OF CHEMISTRY, Issue 9 2007
Dechprasitthichokea Paunpassanan
Abstract Characterization of planting materials used as adsorbent has been studied in order to compare potassium ion adsorption on two types of planting materials, which are a fired planting material (FPM) made from a mixture of 4 kinds of wastes (bottom ash, flue gas desulfurization (FGD) gypsum, paddy soil and sawdust) formed and fired at 850 °C and the commercial planting material called "hydroball" (HDB) bought from Jatujak market, Bangkok. The physical characteristics of both types of planting materials indicate that the FPM has a larger specific surface area than the HDB. The factors affecting potassium adsorption on both the planting materials such as an equilibration time and some solid/solution ratios were investigated. The suitable equilibration time for the adsorption to reach an equilibrium on the FPM and HDB is one and two hours, respectively. The highest amounts of potassium ion adsorbed on both the planting materials were obtained when the solid/solution ratio was 1:15. The adsorption behavior on both the planting materials tends to correspond with the Freundlich isotherm. [source]