جستجوی مقالات مرتبط با کلیدواژه « آب گریزی » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

An emulsion mixture system (usually water, oil and emulsifer) consists of two immiscible phases, the dispersed phase and the dispersion medium (dispersant-continuous). Due to their specifc rheological and physical-chemical properties, emulsions are commonly used in different industries such as cosmetics-pharmaceuticals, food and destruction (road construction, building destruction, etc.). One of the important requirements is appropriate stability of the emulsions over a certain period of time. Emulsions are thermodynamically unstable and several factors affect their instability including the variables of production process and storage conditions. Therefore, emulsifers are suitable to exhibit long-term stability and their performance can be determined by identifying the hydrophilic-lipophilic balance (HLB) characteristic in these compounds. HLB value is a number which is given by the emulsifer to indicate the hydrophilic and lipophilic tendencies of the material. The present work introduces the concept of HLB and methods for determination this character in various ionic and nonionic emulsifers. Considering the relation of the emulsifer HLB to its stability, different methods for evaluation the emulsions stabilities are discussed.

Hypothesis: Gas-liquid membrane contactors have been considered as one of the potential alternatives for CO2 removal compared to conventional technologies. However, membranes wetting with liquid absorbents during this process limits membrane contactors application, which indicates the need for the use of hydrophobic membranes in these systems. In recent years, the use of nanoparticles to increase the hydrophobicity of polymer membrane surfaces and fabrication of nanocomposite membranes has been considerably investigated by researchers. In order to reduce the wetting problem of membranes, in the present work, methyl grafted silica nanoparticles (CH3SiO2 NPs) were used to increase surface hydrophobicity of the polypropylene (PP) hollow fiber membranes, which were synthesized by the sol-gel method. Prepared membranes were characterized by ATR-FTIR, XRD, FE-SEM, contact angle, mechanical strength and breakthrough pressure. Findings: The obtained results from ATR-FTIR analysis confirmed the presence of methyl grafted silica NPs on the surface of PP membrane. The results of the contact angle measurement showed that for nanocomposite membranes by increasing the MTES/TEOS molar ratio from 1 to 4, the contact angle increased from 125° to 164°; however, the contact angle decreased with further increase in the molar ratio of MTES/TEOS. Also, with the precision in the results of mechanical strength measurement, it can be seen that the synthesis of NPs on the membrane surface as well as in the cross-section increased the tensile strength of the membrane to 12.8 MPa. Finally, the performance of membranes was investigated in the membrane contactors for CO2 absorption, which results in a significant decrease in the flux for pure membranes compared with nanocomposite membranes

The most important mechanism of microbially enhanced oil recovery processes is changes in interfacial properties of fluid/fluid/rock affected by bacterial cells and their metabolites. In this study, two bacteria B.licheniformis and P.putida and three different sources of carbon were used. Results showed that due to the effect of carbon source on bacterial growth and also type and value of produced metabolites, changes in interfacial properties of fluid/fluid/rock is affected by used carbon source. The better growth of both bacteria occurred in a culture medium containing glucose. Pendant drop tensiometry, electrophoretic mobility measurement, interfacial dilational rheology and contact angle test were used to investigate the effect of cell structure and culture medium composition on interfacial tension reduction, emulsion stability, and wettability alteration mechanisms. The results of this section showed more potential of P.putida bacteria in surfactant production. Also, results showed that glucose is a better culture medium for B.licheniformis bacteria. Produced biosurfactants and bacterial culture of B.licheniformis bacteria in medium with glucose carbon source reduced surface tension and interfacial tension by 29.07% and 43.87%, respectively. Submerging thin section in glucose culture medium of B.licheniformis bacteria reduced the contact angle of water drop from 109.081 to 44.898°. In the case of P.putida bacteria, the oily and glucose culture media are respectively the effective media for influencing the fluid-fluid and fluid-rock interface. The produced biosurfactants and bacterial culture of P.putida bacteria in medium with olive oil carbon source reduced surface tension and interfacial tension by 36.4% and 27.1%, respectively. The contact angle of drop water was reduced from 109.081 to 54.050° in glucose culture medium of P.putida bacteria

Artworks and historical monuments are often subjected to various damages and deteriorations, according to their age. Damages on artworks or repaired artworks may be provoked by human (vandalism) or by environmental factors such as humidity and light (UV). Nanotechnology provides new methods and innovative ways for the preservation of historical monuments. One of these methods is the preparation of more efficient nanomaterials with smaller particle size, and applying a thin layer coating of materials by different processes such as sol-gel method. In the current study, coating by a variety of conventional polymers is discussed with respect to their protective characteristics of historical monuments in addition to different assessment methods on their protection mechanisms. This study is extended to the important role of organosilicons for preparation of silica nanoparticles and latter protection capacity on coating properties. Another important category of polymers which may provide protective coatings for historical artworks are acrylic polymers. By considering the increasing importance of organic-inorganic hybrids in protection mechanism, some discussions are focused on such hybrids as nanocomposite coatings. The hybrids can be coated on different substrates to impart different properties such as hydrophobicity and anti-graffiti properties. In addition to the use of nanomaterials in conventional polymer coatings for protection and restoration of historical monuments, this paper further explains the preparation of nanomaterials for their usefulness in consolidating wall paintings, removal of aged polymers from historical monuments and enhancing cellulosic paper stability against fungal growth.

Recently, flexible and environmental-friendly aerogel blankets have attracted considerable attention. In this work, the novel silica aerogel/basalt blanket was prepared using basalt fibers via a two-step sol-gel process followed by an ambient drying method and immersing the basalt fiber layer into silica sol. The silica aerogel particles were characterized by FTIR, FE-SEM and nitrogen adsorption analysis. The morphology, hydrophobic properties and surface roughness of neat basalt fiber and its aerogel blanket were also investigated. The density if 0.34 g/cm3, the porosity of 85%, mean pore size of 7±1.5 nm and the surface area of 750 m2/g for the nanostructured silica aerogel particles are obtained. The formation of nanostructured silica aerogel particles on the surface of basalt fibers in the sol-gel process were efficiently occurred leading to a strong hydrophobicity the blanket samples (contact angle of 114°) compared to the hydrophilic neat basalt fibers. The surface roughness of basalt fiber in the blanket samples was increased due to the fiber surface coating with silica aerogel particles. Increasing the sol volume in the synthesis process increased the basalt surface roughness from 3.6μ to 11μ.

To date, by development of inorganic polymer technology and the use of these materials in electronics industry, medical, aerospace, military and other fields, the researchers have shown a growing interest in the synthesis of novel inorganic polymers having specific physical, chemical and electrical properties in their laboratories and industry research and development centers. Polyphosphazenes are one of the most wide-ranging groups of inorganic polymer families, until nowat least seven hundred variations of these polymers have been synthesized. These polymers with unique properties such as self-extinguishing, hydrophobicity, and biocompatibility have attracted the attention of many researchers in polymer science. All these unique properties are related to the main chain of polyphosphazene which has two side groups in each repeating unit; that they can be altered with a wide range of diverse organic compounds simply to indicate various properties. This study aims to contribute to this growing area of research by outlining the structure, synthesis methods and applications of polyphosphazenes.