نشریه پژوهش های کاربردی مهندسی شیمی - پلیمر
پیاپی 1 (پاییز 1396)

The adsorption of polymeric systems onto reservoir rock through altering the wettability of rock surface improves oil recovery and reduces the unwanted water production. . In this study, the adsorption behavior of dilute polymeric systems based on sulfonated polyacrylamide on the glass particles surfaces (representative of sandstone reservoirs) was investigated and the effect of this phenomenon on changing their surface properties was examined. Results show that crosslinked polymeric samples have lower adsorption on glassy surface comparing with uncrosslinked sulfonated polyacrylamide solution. Furthermore, the contact angle tests results showed that crosslinked samples change the surface property of glass particle less than sulfonated polyacrylamide solution. In addition the Langmuir isotherm model fitted the isotherm data better than the Freundlich model for these dilute polymeric systems. Furthermore, study of the thermodynamic of adsorption showed that their adsorption behavior on glassy surfaces is a spontaneous and exothermic process.

Hemodialysis is a process of purifying the blood of a person whose kidneys are not working normally. Polyethersulfone membrane has the most application in blood purification because of its unique features, but its hydrophobic nature results in poor biocompatibility. When PES-based membranes are contacted with blood, proteins tend to adsorb onto the polymer surface, and this protein layer causes any adverse effects such as the coagulation of blood cells and platelet adhesion. The biocompatibility of pristine PES membrane can be improved by different modification methods. The aim of this research is to improve polyethersulfone (PES) membrane hydrophilicity and antifouling properties by adding pluronic F-127, poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO-PPO-PEO) block copolymer, to the dope solution. In this regard, PPO hydrophobic molecules are bound to PES chains due to hydrophobic–hydrophobic interactions, and membrane hydrophilicity would be improved because of hydrophilic PEO segments. To investigate the effect of adding pluronic F-127 on membrane performance, water contact angle, mechanical properties and filtration tests were carried out. Membranes morphology were characterized by SEM microscopy. Results showed that the addition of pluronic F-127 to the polymeric solution caused permeate flux increase up to 554 L/m2h due to membrane pore size growth and contact angle decrease. Moreover, addition of pluronic F-127 caused a decrease in the tensile strength of the PES/Pluronic F-127 membranes. PES/Pluronic F-127 membranes have improved fouling resistance compared to the pristine membrane.

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.

Oil resistant o-rings on the basis of acrylonitrile butadiene rubber (NBR) reinforced by nanoclay were produced via a traditional industrial method in accordance with aviation standard, AMS 7272. The production of nanocomposites comprised the compounding of nanocomposite with optimum mechanical properties and minimum contents of used carbon black and nanoclay, design and manufacturing of the required mold and finally compression molding of the oring. Mechanical and morphological properties of NBR/nanoclay compounds were optimized by introduction of proper contents of a compatibilizer containing a mixture of resorcinol and hexamethylene tetramine through using a master batch production method. The prepared nanocomposites were characterized using X-ray diffraction (XRD) analysis, curing measurements and tensile test analysis. The XRD analysis showed that the compatibilizer facilitates the intercalation of nanoclay silicate layers with the rubber chains which leads to the increase of their basal spacing. The cure characteristics of the nanocomposites showed a decrease of scorch time and increase the cure rate index with the nanoclay loadings. Furthermore, the minimum scorch time and maximum cure rate index could be achieved through using the appropriate content of compatibilizer. The results exhibit that the nanocomposites containing the compatibilizer have higher mechanical properties especially at higher deformations compared to the corresponding uncompatibilized nanocomposites

In this research, closed-cell natural rubber foams were produced using a single-step compression molding. The effect of carbon black content on morphology, physical and mechanical properties of the foams were examined. Results showed that in this methodology, the foam density was independent of reinforcement percentage, which is a unique characteristic of single-step foams that contrasts with other previous observations. The study of curing behavior of foam compounds showed that the carbon black increasing from 0 to 30 phr increased the crosslink density (CLD) from 6.5 to 8.3*10-5 mol/cm3, the cure rate from 16.1 to 23.2 (%/min) and the ultimate torque from 5.8 to 10.4 Nm, while, reduced curing time from 9.2 to 5.8 min. The scanning electron microscope (SEM) results showed that the reinforcement acted as a nucleation agent increasing the cell density from 8 N/cm3 to 140 N/cm3 and reducing the cell size from 579µm to 255µm. The increase of reinforcing content in the produced foams reduced the cells size and enhanced the properties of the rubber matrix. Accordingly, the modulus and hardness of the foams were increased by 0.8MPa and 40 shore A, respectively. Results of sound absorption and reflection showed that the rubber foam reflects the sound waves more than 90% and absorbs waves about 10%.

In this research,nanocomposite coatings based on epoxy containing pristine graphene oxide and starch-modified graphene oxide are prepared and characterized by Fourier transfer infrared spectroscopy, andtheir crosslinking behavior is studied using nonisothermal differential scanning calorimetry.These nanocomposites, because of having platelet-like nanomaterials inside and their organic origin, can be applied as coating on metal surface in diverse industries.The reason behind using starch was its natural basis and abundance of hydroxyl groups in its structure which can take part in crosslinking reaction with epoxide. Neat epoxy systems having amine curing agent, and nanocomposites containing epoxy, amine curing agent, andpristine or starch-modified graphene oxide nanosheets were cure at different heating rates to assess their curing behavior. Change in hearing rate of test caused change in onset and peak temperature of the exotherm curves and consequently heat of reaction changed. It was observed that the presence of the graphene oxide nanosheets hindered the crosslinking reactions, while surface modification of them with starch natural polymer compensated for such a hindrance via catalytic role of starch, and increased crosslink density of system.