دو ماهنامه علوم و تکنولوژی پلیمر
سال سی و پنجم شماره 5 (پیاپی 181، آذر و دی 1401)

The global problem of air pollution and its consequences, as well as the reduction of fossil fuel reserves, have created the need to use alternative energy sources. Therefore, it is necessary to create and develop the required infrastructure of renewable resources in the production of clean energy. In addition, the use of renewable energy sources is essential at all times to replace non-renewable sources continuously The storage of renewable energy, especially on a large scale, is the requirement of this goal. Batteries are one of the most potential technologies for this purpose Currently, lithium ion and flow batteries are the focus of studies for development and commercialization compared to other types of batteries. Flow batteries, especially vanadium type, are more capable of improving components and commercialization for large scale due to the availability of vanadium elements in nature, elimination of the ignition, and cost reduction compared to lithium batteries. One of the main challenges in this type of battery is the development of a high-performance membrane with low cost. Therefore, the description of performance and components of this type of battery, including the role of polymer membrane and characteristics, can create a perspective for its development and commercialization. To this end, in the present paper, the overall structure, performance, and constituent components of this type of battery have been introduced, focusing on the role of polymer membrane and its characteristics as the key component of its technology. Additionally, in each section recent results reported by the researchers have been presented in brief. Finally according to the literature survey, the future perspective, and remaining challenges for the development of this technology are mentioned.

Hypothesis: 

Methyl orange is a dye used in various industries such as printing and dyeing. Since methyl orange is not affected by conventional biological treatment and is not easily decomposed, the release of effluents containing this toxic compound into environment has adverse effects on human life and the aquatic ecosystem. Therefore, it is necessary to remove this dye from various wastewaters Among the common methods of water purification, the method of adsorption by bioadsorbents is considered as a simple, efficient and inexpensive method. In the present study, walnut shell modified with polyaniline nanofibers (PANI/WNS) has been used for removal of methyl orange dye. This modified adsorbent is a good candidate since it has favorable characteristics including suitable morphology and positively charged functional groups for removal of anionic dyes.

PANI/WNS was prepared through aniline polymerization reaction on the surface of walnut shell particles and characterized using FTIR, FESEM, EDX, BET and XRD techniques. The effect of various physical and chemical parameters such as initial pH, contact time, adsorbent dose and initial dye concentration on the removal rate of methyl orange was studied and optimized. Also, thermodynamic parameters such as ΔH, ΔS and ΔG were investigated.

The adsorbent is able to remove methyl orange dye in acidic environment. Optimization of the effective parameters on the adsorption process showed that the maximum methyl orange removal was obtained under conditions of pH 3, contact time of 140 min, adsorbent dosage of 0.35 g/L and dye initial concentration of 50 mg/L. Evaluation of laboratory data by different isotherm models showed that the highest correlation coefficient is related to Langmuir isotherm model and is equal to 0.9975, which indicates that the dye adsorption process is limited to a monolayer Also, the maximum adsorption capacity for methyl orange dye was obtained as 243.9 mg/g at 25°C, which is a significant amount compared to similar adsorbents reported in the literature and indicates the high ability of the studied modified bioadsorbent for removal of anionic dyes such as methyl orange. In addition, based on the results of the kinetic studies, the pseudo-second order model showed a better description of the laboratory data. Thermodynamic studies showed that the adsorption of the dye is a favorable, spontaneous and endothermic process.

Hypothesis: 

Nowadays, polymer nanofibers have been extensively used in different industries especially for medical applications. Electrospinning is a simple, versatile and cost-effective technique to prepare nanofibers. For biomedical applications such as tissue engineering poly(lactic acid) (PLA), a biocompatible and biodegradable polymer, has gained great interest. To improve the physical and mechanical properties of electrospun PLA, nanofibers and nanoparticles can be included.

PLA nanofibers were prepared through electrospinning. Silver nitrate was added to increase the conductivity of electrospinning solution, resulting in finer nanofibers. To improve morphology and mechanical properties of the electrospun fibers, silicone rubber nanoparticles (NSR) were added into the electrospinning solution. Scanning and transmission electron microscopies (SEM and TEM) were employed to investigate the morphology of electrospun nanofibers and dispersion of nanoparticles, respectively. To investigate thermal and mechanical properties of the obtained nanofibers, differential scanning calorimetry (DSC) and tensile test were used.

To obtain poly(lactic acid) electrospun nanofibers with fine and defect-free morphology, PLA was dissolved in a mixture of dichloromethane and dimethylformamide (DCM/DMF) solvents with a volumetric ratio of 3/2 Electrospinning solution with 7% poly(lactic acid) containing 0.5% (by wt) silver nitrate led to defect-free nanofibers with a diameter of less than 200 nm. Inclusion of silicone rubber nanoparticles of 1% resulted in finer nanofibers with a diameter of about 123 nm. This was attributed to enhanced elasticity of the solution with addition of elastomeric nanoparticles. Adding silicone rubber nanoparticles increased the cold crystallization temperature and decreased the crystallinity of polylactic acid. Toughness of nanofibers considerably increased in the presence of silicone rubber nanoparticles without sacrificing modulus and strength, indicating high capability of NSR as an impact modifier

Hypothesis: 

Among the types of bioplastics, poly(lactic acid) (PLA) has the ability to compete with petroleum-based polymers due to its favorable properties such as high tensile strength and high modulus of elasticity. Brittleness is the main disadvantage of PLA which limits its practical applications in some industrial fields like packaging and textile. Blending of PLA with other flexible bioplastics like polycaprolactone (PCL) and adding nanoparticles like graphene into PLA are among the techniques that can be used to balance the stiffness and toughness of PLA.

Nanocomposites based on PLA/PCL/graphene (G) were prepared by melt mixing using an internal mixer with direct feeding method. In all samples the weight ratio of PCL dispersed phase to PLA matrix phase was 30:70, and three different weight percentages of nanographene (0.5, 1 and 2) were used. A rheometric mechanical spectrometer (RMS), X-ray diffractometer (XRD), and a scanning electron microscopy (SEM), as well as tensile and differential scanning calorimetry (DSC) measurements were used to study the microstructure, morphology, mechanical and thermal properties, respectively.

The results of XRD showed that graphene nanoparticles are well dispersed in the polymer matrix. The SEM results demonstrated that incorporation of graphene nanoparticles into the PLA/PCL sample led to a decrease in the PCL droplet size. The melt linear viscoelastic measurements showed that incorporation of 2% (by wt) of nanographene into PLA/PCL sample enhanced the storage modulus and complex viscosity by about 200 and 400% due to well-dispersion of nanoparticles in the matrix that led to the formation of a 3D network between nanographene and/or nanographene-polymer chains. The tensile test results showed that the elastic modulus tensile strength, and elongation-at-break increased by 126.63%, 80.48%, and 97.36% respectively, by adding 2% graphene nanoparticles to the PLA/PCL sample. The results of the thermal tests also showed that the addition of nanographene and PCL to the PLA polymer causes the nucleation effect and the creation of active nucleation centers, and the crystallinity percentage of the PLA phase increases, but the effect of PCL in this research was more evident than that of nanographene.

Hypothesis: 

To enhance the crack growth resistance of rubber composites one strategy is to embed mechanisms for viscoelastic dissipation. This can be fulfilled by enlarging the bound rubber content through either increasing the filler-filler or filler-polymer interactions. Improving the filler-polymer interaction through surface modification of silica by silanes is not a favorable route because of the adverse impact of surface modification on lowering the share of filler-filler interaction on the bound rubber content. Modification of the rubber backbone appears to be a proper alternative. The difference in the .performance of these two methods can be observed well in peroxide-cured rubbers

Present contribution performs a comparative study on the impact of modification in rubber or reinforcing silica on the crack growth resistance of peroxide-cured natural rubber (NR). For NR/silica composites, the modifications in rubber and silica are respectively conducted by grafting maleic anhydride or the bi-functional silane of bis(triethoxysilylpropyl)tetrasulfide (TESPT). For the case of maleic anhydride grafting, the influence of initiation by thermal and chemical routes is also compared

Results revealed that the modification of the rubber with maleic anhydride leads to an increase in the polymer-filler interactions and the bound rubber content. This imparts a favorable balance in mechanical strength and resistance to crack growth of the resulting composite. Tearing resistance of the system containing maleated rubber in the high loading range of silica showed a significant increase of about 150% compared to a neat rubber system filled with unmodified silica. It was suggested that the chemical crosslink density and viscoelastic dissipation are, respectively, the controlling mechanisms of tear resistance in low and high loading range of silica.

Hypothesis:

 Carbxylated graghene oxide nanosheets were synthesized and the nanosheets were applied to the surface modification of the polyethersulfonebased nanofiltration membranes for water treatment.

Different concentrations of the synthesized carboxylated graphene oxide nanosheets were used as the surface modifiers to prepare the PES/PEI c-GO nanofiltration membranes. The prepared membranes were analyzed by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), 3D surface images (AFM) and X-ray diffraction (EDX) spectroscopy. The permeability and the separation performance of the constructed membranes were evalueted by the water contact angle, water content, the flow of pure water and the rejection of sodium sulfate salt and heavy metals.

the FTIR analysis showed the formation of favorable bonds in the synthesized carboxylated graphene oxide nanosheets and the fabricated membranes. The membrane surface modification by c-GO nanosheets led to a decrease in membrane roughness and the contact angle decreased from 75° for the neat membrane to 36° for M1 at 0.001 g of carboxylated graphene oxide nanosheets. Moreover, the water content increased and M2 showed the highest water content. The highest pure water flux was obtained at 13.065 L/m2.h for the constructed M2 membrane containing 0.01 g of carboxylated graphene oxide nanosheets. In addition, the highest rejection of sodium sulfate salt (Na2SO4) was observed 67.5 % for the M3 membrane containing 0.1 g of c-GO nanosheets and the highest rejection of copper nitrate (Cu(NO3)2) was obtained 87.21% for the M1 membrane containing 0.001 g of c-GO nanosheets. Furthermore the obtained results indicated the improvement of the anti-fouling properties of the modified membranes containing carboxylated graphene oxide nanosheets compared to the base membrane.