نشریه پژوهش های کاربردی مهندسی شیمی - پلیمر
سال سوم شماره 3 (پیاپی 9، پاییز 1398)

Poor mechanical strengths and lack of thermal stabilities of hydrogels confine their extensive practical applications in many areas. The growing scientific need for solving this problem and achievement to the hydrogels with improved properties has led to the design and production of the nanocomposite hydrogels.

The polymeric networks of nanocomposite hydrogels compared to the ordinary hydrogels have improved elasticity and rheological properties. Other points that increase the importance of structural studies of nanocomposite hydrogels are the high strength of these materials versus the application of external forces, as well as maintaining its structure against increasing of temperatures. In this regard, the type and amounts of nanomaterial, the preparation method and formation of hydrogel network have a significant role in improving the physical, chemical and biological properties of hydrogels, and, it must be noted that these parameters will depend on the application of nanocomposite hydrogels. This also highlights the need for the production of nanocomposite tailored hydrogels. Therefore, orientation of the range of nanomaterials, the preparation method and product identification, along with sufficient information on the application of these materials, might have an important role in ensuring the success of these materials, requiring comprehensive library research and studies on polymerization processes, morphology and rheology.

In this review article, the scientific advances in the field of nanocomposite hydrogels, focusing on its types based on the type of nanoparticles, its properties, preparation methods, identification methods with a new perspective on rheology, thermal analysis and morphology is investigated. Finally, the applicability of these materials is collected in a comprehensive table in various fields such as tissue engineering, enhanced oil recovery, agriculture, and etc… .

The enhancement of energy consumption and increasing demand for oil have led to using improve oil recovery methods. Chemical enhanced oil recovery methods are among the most widly used techniques. Generally, the effect of these methods has been less than the predicted amounts by the studies. One of the leading causes, could be due to the loss of chemicals by adsorption or precipitation of the surfactants on the rock surface. The mineralogy of the reservoir rocks is effective in determination of the interaction between the bulk of the fluid phase and rock surface. This effect will change in the surface charge of the adsorbent and wettability alteration of the rocks.

In this study, the adsorption of AOT surfactant on the surface of a hydrophilic adsorbent of carbonate reservoir was investigated. For this purpose, after the preparation of rock and fluid samples, the adsorption of surfactant was investigated in concentrations below and above the CMC.

Batch adsorption experiments were conducted to measure the amount of surfactant adsorption on the surface of carbonate rock. First different concenteration of AOT solutions and carbonate rock as adsorbent were combined. After 48h, the equilibrium concentrations were determined by using the calibration curve and. The amount of surfactant adsorption can be calculated by knowing the maqnitudes of equilibrium and initial concentration of the surfactant.

The results showed that by increasing the concentration of the surfactant in the liquid phase, the adsorption increased until it reaches a saturation point at the concentration of 1200 ppm. The results of the modeling showed that the Freundlich equilibrium isotherm with 1⁄n equals 0.8971 was the best fit for describing the prediction of AOT surfactant adsorption behaviour.

Superabsorbent hydrogel is a three-dimensional hydrophilic polymer that can absorb and store large amounts of water and aqueous solutions. Among various polymers, the chitosan as a biodegradable and non-toxic polymer has been widely used to fabricate superabsorbent hydrogels. In this research, a nanohydrogel composed of chitosan, acrylic acid and silver nanoparticles was synthesized by radical polymerization at 60 Co. Swelling properties of chitosan/nanosilver/acrylic acid hydrogel were studied and then this hydrogel was treated under  ultrasonication. Finally, this hydrogel was coated on paper samples with 0, 1, 1.5 and 2 w % of hydrogel. FTIR spectroscopy was used to determine the functional groups and dynamic light scattering method (DLS) was applied to identify the size of hydrogel’s nano and microparticles The images of scanning electron microscopy (SEM) showed a hydrogel coating on paper and water stress tests revealed that adding 0% to 1.5 w% of nanohydrogels to the paper surface increased its water absorption from 64.3% to 95.5%. Other worthwhile fact was that that the addition of silver nanoparticles effectively facilitated the formation of a three-dimensional hydrogel structure and increased the water swelling in nanohydrogel from 130 ± 10 g / g to 232 ± 7 g / g.

In this study, the three phase mixed matrix membranes comprising Pebax®1657, PEG-200 and MIL-53(AL) nanoparticles were evaluated for CO2 gas separation. The effect of various PEG-200 and MIL-53(AL) concentration within the pebax polymeric matrix on the structure, gas permeability, and selectivity of the membranes was investigated. To study the cross-sectional morphology, crystallinity and thermal properties of the synthesized membranes, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were utilized, respectively. Fourier transform infrared (FT-IR), was also carried out to identify the formation of the chemical bonds in the membrane. SEM images demonstrated a uniform cross-section and admissible dispersion of nanoparticles. The results of the thermal analyses indicated an increase in crystallinity and Tg in presence of MIL-53 particles. Permeation of pure gases (i.e., CO2, CH4) through the prepared neat Pebax®1657, the blended Pebax/PEG-200 and the Pebax/PEG-200/MIL-53(AL) mixed matrix membrane was measured at the pressure of 2–10 bar and temperature of 30 °C. The results showed that at the pressure 10 bar, the CO2 gas permeation from 133.36 barrer in pure membrane increased to 311.7 barrer (134%) in a membrane containing 10%wt MIL-53.

The aim of this project is the design and optimization of the formulation of epoxy adhesives for bonding metal to composite parts . This joints are most widely used in the aerospace industry to reduce stress concentration at a point. Joints for single edge joining include stainless steel metal with commercial code 316L and composite epoxy resin / carbon fiber. In this study, the effect of three types of additives: filler (alumina micro-particles), nylon 6.6 and phenolic resin (type of resin) on the mechanical and thermal properties of epoxy adhesive have been investigated. Tensile test results showed that increasing alumina fillers increases the tensile strength and overlap shear adhesive samples, respectively, in single lap joint dumbbells and elderly. The test showed that increasing the amount of nylon 6.6 When is slightly higher due to a sharp drop in tensile strength and overlap shear, respectively, in both cases is dog bone and single lap joint adhesives. This limit depends on the capacity epoxy ring to absorb amide hydrogens. The test for thermal properties (TGA) showed that increasing the amount of phenolic thermal stability is improved. High-temperature tensile test of appropriateness is also increasing impact of phenolic resin. Finally, the adhesive properties built with the similar adhesive (UHU) were compared. Results showed superiority in single lap joint metal to composite adhesive is made in the study.

In this study, the use of a mixed alumina and aluminum sulfate powder has been studied on thermal conductivity of butyl rubber filled with carbon black used as curing tire bladder composite. The aforementioned filler was added to 1.5 parts by weight in a blend of Bladder. The mixtures were prepared in the internal mixer and the curing characteristics, the mechanical and aging properties as well as the heat conductivity behavior of the composites were measured. To determine the coefficient of thermal diffusion of rubber composite, an immersion sampling method with specific dimensions in the oil bath and heat transfer computer simulation was used using a guessing and error approach. It was observed that the thermal diffusion coefficient of the above mixture rises from an average of 1×10-7 m2/s  to an average of 1.3 ×10-7 m2/s  without changing the mechanical and aging properties of the mixture. In the following, by choosing a simplified geometry from the tire profile in the near-tire curing conditions, and by simulating heat transfer behavior through the ABAQUS software, the effect of this increase on the thermal diffusivity coefficient was studied on the temperature variations of the inner parts of the tire. It was observed that the temperature of the different points of  tire is affected by increasing the thermal conductivity of the tire, Therefore, there is a good potential for reducing the curing time of the tire.