Macroporous Thermosets via Chemically Induced Phase Separation

1996 ◽  
Vol 431 ◽  
Author(s):  
J. Kiefer ◽  
R. Porouchani ◽  
D. Mendels ◽  
J. B. Ferrer ◽  
C. Fond ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
New Technology ◽  
Curing Temperature ◽  
Low Molecular Weight ◽  
Closed Cell ◽  
Chemically Induced

AbstractWe have explored a new technology based on chemically induced phase separation that yields porous epoxies and cyanurates with a closed cell morphology and micrometer sized pores with a narrow pore size distribution. When the precursor monomers are cured in the presence of a low molecular weight liquid, the desired morphology results from a phase separation and a chemical quench. After phase separation, the porosity is achieved by thermal removal of the secondary liquid phase, specifically by diffusion through the crosslinked matrix. In respect to the thermodynamics and kinetics, the origin of the phase separation process can be identified as nucleation and growth. The influence of internal and external reaction parameters, such as chemical nature of the low molecular weight liquid, its concentration and the curing temperature on the final morphology are presented. Thus, the morphology can be controlled ranging from a monomodal to bimodal pore size distribution with pore sizes inbetween 1 to 10 μm. These porous thermosets are characterized by a significantly lower density, without any loss in thermal stability compared to the neat matrix. Such new materials demonstrate great interest for lowering the dielectric constant and for improving the fundamental understanding of the role of voids in stress relaxation and toughening.

Preparation and Mechanism of Interconnected Mesoporous Carbon Monoliths from Phenolic Resin/Ethylene Glycol Mixtures

2012 ◽  
Vol 512-515 ◽  
pp. 403-406 ◽  
Author(s):  
Gang Zhang ◽  
Ze Wen Xiao ◽  
Guan Jun Qiao
Keyword(s):  
Phase Separation ◽  
Ethylene Glycol ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Mesoporous Carbon ◽  
Phenolic Resin ◽  
Fractal Dimensions ◽  
Mesoporous Structure ◽  
Curing Temperature

The preparation of interconnected mesoporous carbon monoliths (MCMs) derived from phenolic resin/ethylene glycol mixtures based on polymerization-induced phase separation have been investigated for fabrication of complex-shape SiC ceramics. The effect of the ethylene glycol content, curing catalyst and the curing temperature on the pore structure and pore distribution of carbon monoliths has also been studied, with emphasis on controlling the apparent porosity and pore size distribution. Fractal dimensions (DF) was proposed to evaluate the morphologies of carbon monoliths by using the box counting method. The results show that interconnected mesoporous carbon monoliths with narrow pore size distribution were obtained by changing the curing temperature and the content of ethylene glycol, curing catalyst in the resin mixtures and its mechanism was discussed in this paper. In this paper, interconnected mesoporous structure was attributed to the mechanism of spinodal decomposition (SD), which was discussed in detail. Carbon monoliths inherit their porosity from cured resins where it was formed as a result of phase separation of resin-rich and glycol- rich phases.

scholarly journals Effect of the Nano-Ca(OH)2 Addition on the Portland Clinker Cooking Efficiency

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1787
Author(s):  
Azzurra Zucchini ◽  
Paola Comodi ◽  
Alessandro Di Michele ◽  
Riccardo Vivani ◽  
Lucia Mancini ◽  
...  
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Energy Saving ◽  
Size Distribution ◽  
New Technology ◽  
Low Energy ◽  
Free Lime ◽  
Work Index ◽  
Lime Concentration ◽  
Clinker Production

A new technology was tested to improve the cooking efficiency of the raw mixture for Portland clinker production by the use of nano-Ca(OH)2. A decrease in the free lime concentration after the firing of approximately 35% and 55% in the nano-added clinkers burned at 1350 °C and 1450 °C, respectively, with respect to the standard Portland clinkers was observed. Moreover, in the nano-added clinkers, a slight decrease in alite (C3S), of approximately 2–4 wt%, and increase in belite (C2S), of approximately 5–6 wt%, were observed. Despite these variations, the C2S and C3S abundance lies within the ranges for standard Portland clinkers. The results showed that the nano-addition leads to an increase of the raw mixtures’ cooking efficiency. The relatively low energy required for the clinker firing could be used to increase the plant productivity and decrease the CO2 emissions during clinker burning. The decrease of the work index of the clinkers produced by the use of the nano-Ca(OH)2 also contributes to the energy saving during clinker grinding. Differences were also found in the pore size distribution among nano-added clinkers and the standard Portland clinker. The smallest porosities with the modal volume lying in the class of 3 × 10−6 mm3 were found to increase by the use of nano-Ca(OH)2. However, the pore volumes higher than 2.0 × 10−5 mm3 decreased in the nano-added clinkers.

Pore Structure Of Hydrated Cement Determined By Mercury Porosimetry And Nitrogen Sorption Techniques.

1988 ◽  
Vol 137 ◽  
Author(s):  
Yahia Abdel-Jawad ◽  
Will Hansen
Keyword(s):  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Pore Volume ◽  
Mercury Porosimetry ◽  
Total Pore Volume ◽  
Curing Temperature ◽  
Vycor Glass ◽  
Degree Of Hydration

AbstractThe pore structure (i.e. total pore volume, surface area and pore-size distribution curves) was measured using mercury porosimetry and nitrogen sorption. Hydrated portland cement (type I) of water-cement (w/c) ratios 0.3, 0.4 and 0.6 by weight was analyzed at three degrees of hydration (i.e., 30%, 50% and 80%; 70% for the 0.3 w/c system) corresponding to low, intermediate and high levels of hydration. The effect of curing temperature (3°, 23°, and 43°C) on pore structure was also studied. The two techniques were evaluated as well on porous Vycor glass, which has a narrow pore size distribution in the size range accessible to both. Results obtained by both techniques on porous Vycor glass agreed well. However neither technique can be used alone to study the entire pore structure in well-hydrated cement due to the wide range in pore sizes and the presence of micropores. Due to the unstable pore structure in cement a specimen treatment procedure such as methanol replacement, combined with volume-thickness (V-t) analysis, is necessary in order to measure the micropores. At low hydration values the pore structure can be estimated by mercury intrusion porosimetry (MIP). At higher hydration values, however, this technique underestimates total pore volume and surface area due to the presence of micropores which MIP cannot determine. In the pore size range of overlap, higher pore volumes were obtained with MIP. Nitrogen V-t analysis shows that micropores are more pronounced with lower w/c ratios. This finding is consistent with pore size distribution curves obtained by MIP. For a given w/c ratio and degree of hydration the total pore volume measured by MIP was found to be independent of curing temperature in the temperature range studied. At any w/c ratio, capillary porosity is controlled by degree of hydration alone.

scholarly journals How Molecular Weight Cut-Offs and Physicochemical Properties of Polyether Sulfone Membranes Affect Peptide Migration and Selectivity during Electrodialysis with Filtration Membranes

Membranes ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 153 ◽  
Author(s):  
Sabita Kadel ◽  
Geneviève Pellerin ◽  
Jacinthe Thibodeau ◽  
Véronique Perreault ◽  
Carole Lainé ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Physicochemical Properties ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Negative Charge ◽  
Protein Hydrolysate ◽  
Filtration Membranes ◽  
Polyether Sulfone ◽  
Wide Range

Filtration membranes (FMs) are an integral part of electrodialysis with filtration membranes (EDFM), a green and promising technology for bioactive peptide fractionation. Therefore, it is paramount to understand how physicochemical properties of FMs impact global and selective peptide migration to anionic (A−RC) and cationic (C+RC) peptide recovery compartments during their simultaneous separation by EDFM. In this context, six polyether sulfone (PES) membranes with molecular weight cut-offs (MWCO) of 5, 10, 20, 50, 100 and 300 kDa were characterized and used during EDFM to separate peptides from a complex whey protein hydrolysate. Surface charge, roughness, thickness and surface/pores nature of studied PES membranes were similar with small differences in conductivity, porosity and pore size distribution. Interestingly, global peptides migration to both recovery compartments increased linearly as a function of MWCO. However, peptide selectivity changed according to the recovery compartments and/or the peptide’s charge and MW with an increase in MWCO of FMs. Indeed, in A−RC, the relative abundance (RA) of peptides having low negative charge and MW (IDALNENK and VLVLDTDYK) decreased (45% to 19%) with an increase in MWCO, while the opposite for peptides having high negative charge and MW (TPEVDDEALEK, TPEVDDEALEKFDK & VYVEELKPTPEGDLEILLQK) (increased from 16% to 43%). Concurrently, in C+RC, regardless of MWCO used, the highest RA was observed for peptides having low positive charge and MW (IPAVFK & ALPMHIR). It was the first time that the significant impact of charge, MWCO and pore size distribution of PES membranes on a wide range of MWCO was demonstrated on EDFM performances.

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