Tailoring the Pore Size of Hypercrosslinked Polymer Foams

1996 ◽  
Vol 431 ◽  
Author(s):  
W. P. Steckle ◽  
M. A. Mitchell ◽  
P. G. Apen
Keyword(s):  
Pore Size ◽  
Polyaromatic Hydrocarbons ◽  
Crosslinking Agent ◽  
Nitrogen Adsorption ◽  
Total Surface Area ◽  
Pore Sizes ◽  
Surface Areas ◽  
Small Pore ◽  
High Resolution Tem ◽  
Cure Time

AbstractOrganic analogues to inorganic zeolites would be a significant step forward in engineered porous materials and would provide advantages in range, selectivity, tailorability and processing. Rigid molecular foams or “organic zeolites” would not be crystalline materials and could be tailored over a broader range of pore sizes and volumes. A novel process for preparing hypercrosslinked polymeric foams has been developed via a Friedel-Crafts polycondensation reaction. A series of rigid hypercrosslinked foams have been prepared using simple rigid polyaromatic hydrocarbons including benzene, biphenyl, m-terphenyl, diphenylmethane, and polystyrene, with p-dichloroxylene (DCX) or divinylbenzene (DVB) as the crosslinking agent. Transparent gels are formed suggesting a very small pore size. After drying the foams are robust and rigid. Densities of the resulting foams can range from 0.15g/cc to 0.75g/cc. Nitrogen adsorption studies have shown that by judiciously selecting monomers and crosslinking agent along with the level of crosslinking and the cure time of the resulting gel, the pore size, pore size distribution, and the total surface area of the foam can be tailored. Surface areas range from 160 to 1,200 m2/g with pore sizes ranging from 6Å to 2,000Å. Further evidence of the uniformity of the foams and their pore sizes has been confirmed by high resolution TEM.

Validity of the Kelvin equation in estimation of small pore size by nitrogen adsorption

1997 ◽  
Vol 275 (12) ◽  
pp. 1156-1161 ◽  
Author(s):  
T. Takei ◽  
M. Chikazawa ◽  
T. Kanazawa
Keyword(s):  
Pore Size ◽  
Nitrogen Adsorption ◽  
Kelvin Equation ◽  
Small Pore Size ◽  
Small Pore

scholarly journals Monitoring of the Variation in Pore Sizes of Woven Geotextiles with Uniaxial Tensile Strain

2021 ◽  
Vol 12 (1) ◽  
pp. 374
Author(s):  
Wenfang Zhao ◽  
Xiaowu Tang ◽  
Keyi Li ◽  
Jiaxin Liang ◽  
Weikang Lin ◽  
...  
Keyword(s):  
Pore Size ◽  
Tensile Strain ◽  
Pore Diameter ◽  
Filter Design ◽  
Uniaxial Tensile ◽  
Distribution Diagram ◽  
Pore Sizes ◽  
Large Pore ◽  
Small Pore ◽  
Pore Opening

Characteristic pore-opening size O95 or O90 has been widely used in the filter design of woven geotextiles. These manufactured products have different pore size proportions of large pore diameters, medium pore diameters, and small pore diameters, respectively. Therefore, uncertainties still exist regarding the prediction of geotextile pore diameter variations under the uniaxial tensile strain. This paper investigates the variations in five characteristic pore-opening sizes O95, O80, O50, O30, and O10, with uniaxial tensile strain by using the image analysis method. The large pore diameters, medium pore diameters, and small pore diameters show different variation behaviors as the uniaxial tensile strain increases. Fifteen specific pores are selected and then their pore diameter variations are monitored under each tensile strain of 1%. The colorful pore size distribution diagram is a visual way to identify the variation of pores arranged in the tension direction (warp direction) and the direction perpendicular to tensile loads (weft direction). The various pore diameters are proved to agree well with the bell-shaped Gaussian distribution. The results exhibit an accurate prediction of the variation in large pore sizes, medium pore sizes, and small pore sizes, respectively, for all tested woven geotextiles with uniaxial tensile strain.

Preparation of Carbon Nanotubes by Using Mesoporous Silica

2001 ◽  
Vol 675 ◽  
Author(s):  
Shinji Kawasaki ◽  
Shingo Komiyama ◽  
Shigekazu Ohmori ◽  
Akifumi Yao ◽  
Fujio Okino ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Mesoporous Silica ◽  
Pore Size ◽  
Present Method ◽  
Pore Sizes ◽  
Small Pore Size ◽  
Small Pore ◽  
Uniform Diameter ◽  
20 Nm

ABSTRACTCarbon nanotubes were synthesized using several mesoporous silica templates with different pore sizes in order to investigate the possibility of controlling the diameter of carbon nanotubes by changing the pore size of the mesoporous silica. TEM observation confirmed that carbon nanotubes with uniform diameter can be obtained by the present method. However, it was found that it is difficult to prepare carbon nanotubes having diameter smaller than ∼20 nm by the present method even if the template with small pore size is used.

scholarly journals Statistical Analysis of Synthesis Parameters to Fabricate PVDF/PVP/TiO2 Membranes via Phase-Inversion with Enhanced Filtration Performance and Photocatalytic Properties

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 113
Author(s):  
Erika Nascimben Santos ◽  
Ákos Fazekas ◽  
Cecilia Hodúr ◽  
Zsuzsanna László ◽  
Sándor Beszédes ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Statistical Analysis ◽  
Pore Size ◽  
Polyvinylidene Fluoride ◽  
Phase Inversion ◽  
Pure Water ◽  
Water Flux ◽  
Pore Sizes ◽  
Small Pore ◽  
Pure Water Flux

Non-solvent induced phase-inversion is one of the most used methods to fabricate membranes. However, there are only a few studies supported by statistical analysis on how the different fabrication conditions affect the formation and performance of membranes. In this paper, a central composite design was employed to analyze how different fabrication conditions affect the pure water flux, pore size, and photocatalytic activity of polyvinylidene fluoride (PVDF) membranes. Polyvinylpyrrolidone (PVP) was used to form pores, and titanium dioxide (TiO2) to ensure the photocatalytic activity of the membranes. The studied bath temperatures (15 to 25 °C) and evaporation times (0 to 60 s) did not significantly affect the pore size and pure water flux of the membranes. The concentration of PVDF (12.5 to 17.5%) affected the viscosity, formation capability, and pore sizes. PVDF at high concentrations resulted in membranes with small pore sizes. PVP affected the pore size and should be used to a limited extent to avoid possible hole formation. TiO2 contents were responsible for the decolorization of a methyl orange solution (10−5 M) up to 90% over the period studied (30 h). A higher content of TiO2 did not increase the decolorization rate. Acidic conditions increased the photocatalytic activity of the TiO2-membranes.

scholarly journals Comparison of Mercury Intrusion and Nitrogen Adsorption Measurements for the Characterization of Certain Natural Raw Materials Deposits

2010 ◽  
Vol 7 (1) ◽  
pp. 621-630
Author(s):  
Baghdad Science Journal
Keyword(s):  
Pore Size ◽  
Gas Adsorption ◽  
Raw Materials ◽  
Mercury Porosimetry ◽  
Construction Materials ◽  
Nitrogen Adsorption ◽  
Distribution Data ◽  
Active Components ◽  
Surface Areas ◽  
Wide Range

The porosity of materials is important in many applications, products and processes, such as electrochemical devices (electrodes, separator, active components in batteries), porous thin film, ceramics, soils, construction materials, ..etc. This can be characterized in many different methods, and the most important methods for industrial purposes are the N2 gas adsorption and mercury porosimetry. In the present paper, both of these techniques have been used to characterize some of Iraqi natural raw materials deposits. These are Glass Sand, Standard Sand, Flint Clay and Bentonite. Data from both analyses on the different types of natural raw materials deposits are critically examined and discussed. The results of specific surface areas showed considerable difference between the two sets of data on the same material. This indicates that the material have an external surface which can not be measure by mercury porosimeter. Also pore size distribution data obtained from N2 adsorption measurements shows a wide range of the smallest pore size. This result suggests that materials have micropores using IUPAC definitions of pore size.

scholarly journals Comparison of Nitrogen Adsorption and Mercury Penetration Results

1988 ◽  
Vol 5 (1) ◽  
pp. 76-93 ◽  
Author(s):  
Bruce D. Adkins ◽  
Burtron H. Davis
Keyword(s):  
Surface Area ◽  
Pore Volume ◽  
Narrow Range ◽  
Nitrogen Adsorption ◽  
Bet Surface Area ◽  
Pore Sizes ◽  
Surface Areas ◽  
Bet Method ◽  
Crystallite Sizes ◽  
Materials Used

Mercury penetration pore volumes obtained for four materials (two silicas, alumina and zirconia) agreed closely with the “Gurvitsch Volume” obtained from nitrogen adsorption. The pore volume of the materials used in this study was found in a narrow range of pore sizes that are amenable to both mercury penetration and nitrogen adsorption measurements. The average crystallite sizes calculated from the BET surface area and from TEM measurements agreed closely except for the highest surface area (310 m2/g) material. The surface areas obtained from mercury penetration or the BET method agree closely for the two lower area materials but the mercury penetration is much higher than the nitrogen surface area for the two higher area materials.

scholarly journals Infuence of Microstructure in Drug Release Behavior of Silica Nanocapsules

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Gema Gonzalez ◽  
Amaya Sagarzazu ◽  
Tamara Zoltan
Keyword(s):  
Pore Size ◽  
Drug Loading ◽  
Morphological Characteristics ◽  
Nitrogen Adsorption ◽  
Release Process ◽  
Al Content ◽  
Surface Areas ◽  
Transmission Electron ◽  
Good Potential ◽  
Model Drug

Meso- and nanoporous structures are adequate matrices for controlled drug delivery systems, due to their large surface areas and to their bioactive and biocompatibility properties. Mesoporous materials of type SBA-15, synthesized under different pH conditions, and zeolite beta were studied in order to compare the different intrinsic morphological characteristics as pore size, pore connectivity, and pore geometry on the drug loading and release process. These materials were characterized by X-ray diffraction, nitrogen adsorption, scanning and transmission electron microscopy, and calorimetric measurements. Ibuprofen (IBU) was chosen as a model drug for the formulation of controlled-release dosage forms; it was impregnated into these two types of materials by a soaking procedure during different periods. Drug loading and release studies were followed by UV-Vis spectrophotometry. All nano- and mesostructured materials showed a similar loading behavior. It was found that the pore size and Al content strongly influenced the release process. These results suggest that the framework structure and architecture affect the drug adsorption and release properties of these materials. Both materials offer a good potential for a controlled delivery system of ibuprofen.

Sign in / Sign up

Export Citation Format

Share Document