دو ماهنامه علوم و تکنولوژی پلیمر
سال سی و ششم شماره 4 (پیاپی 186، مهر و آبان 1402)

Unsaturated polyester resins (UPRs) including ortho, iso, bisphenolic and vinylester are the most widely used thermosetting polymeric resins in the form of coating and matrix in the industry, making up around three quarters of all thermoset resins used in the industry. The major advantages of UPRs include low cost, low viscosity, good mechanical properties and chemical resistance, lightness, low moisture absorption, curing without the formation of volatiles, and simple processing with conventional processing methods. UPRs have been used  in a wide variety of applications including composites, coatings, sealants, chemical and fuel storage tanks, and high-performance components for the construction, marine and land transportation, and electrical industries. However their high shrinkage after curing, low fire resistance and  environmental pollution due to volatile styrene have limited their use. In the past decades, the use of nanofillers in polymers to form polymer nanocomposites has attracted attention due to the ability to combine the advantages of nanofillers and polymers. In addition, the development of nanocomposites of UPRs has made these resins desirable for current and emerging applications that require high specific strength, electromagnetic shielding and improved thermal stability. However, due to the high tendency of nanoparticles to agglomerate, the main challenge in the preparation of nanocomposites is to achieve a homogeneous distribution of nanofillers in the matrix, which is the main key to achieving the desired properties. Therefore, the aim of this study is to evaluate extensive research in this field and to recognize the existing limitations related to the manufacture of these nanocomposites. For this purpose, firstly, the types of nanofillers are categorized and the mixing of nanofillers with UPRs is introduced. Then, the effect of adding nanofillers on the properties of these nanocomposites is reviewed according to the research works done in this field.

Today, the economic growth of countries depends on the supply of energy resources. In most countries, these resources include coal, oil, natural gas, and nuclear energy. However, the use of these resources faces various challenges, including the depletion of fossil fuel resources, environmental pollution and an escalating price. In order to reduce global reliance on finite natural resources and environmentally destructive fuels, many efforts have been made to replace them with renewable resources, such as solar energy, water, wind, and etc. Batteries are one of the most potential technologies for this purpose. Lithium batteries have become increasingly important energy storage systems in our daily lives, which play a significant role in electronics and electric vehicles. However, their practical applications are plagued by the safety issues from liquid electrolytes, especially when the batteries are exposed to mechanical, thermal, or electrical abuse conditions. Polymer electrolytes are being proposed as an alternative liquid electrolyte for building safer lithium batteries. In this review article, polymer electrolytes are divided into two large categories of solid polymer electrolytes and gel polymer electrolytes. The characteristics and properties of solid polymer electrolytes and gel polymer electrolytes are presented at the first. Then, the recent progress of common polymers, namely, poly(ethylene oxide), poly(methyl methacrylate), polyacrylonitrile, poly(vinylidene difluoride) and poly(vinylidene fluoride-hexafluoropropylene) copolymer, biopolymers (cellulose, polyurethane, polycaprolactone), polycarbonate and polysiloxanes as polymer host of polymer electrolytes will be discussed. Finally, we will discuss remaining challenges and future perspectives of the polymer electrolytes for high-performance lithium batteries. We hope that this paper can provide useful information for the development of new polymer electrolytes with excellent properties for use in lithium batteries.

Hypothesis:

 This study constituted the effect of chitosan-zeolite active nanocomposite layer formation on the morphological, physico-chemical and separation properties, as well as the anti-fouling performance of the polyethersulfone-based nanofiltration membrane.

The nanofiltration-based membrane was prepared by phase inversion method and its surface was modified through the dip-coating technique in the polymeric solution. The properties of the prepared membranes were investigated by Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM), 3D surface images, contact angle, water content, pure water flux, salt and heavy metal rejection and anti-fouling performance techniques. 

The FTIR analysis results confirmed the formation of the chitosan/zeolite nanocomposite layer on the polyether sulfone-based membrane. Moreover, the scanning electron microscopy images of the surface and cross-section of the prepared membranes showed the formation of an active layer on the membrane surface. The results of surface analysis showed that the surface modification reduced the surface roughness of the membrane. In addition, the use of zeolite nanoparticles on the surface layer caused to an increase in the membrane water content. The pure water flux of bi-layer modified membrane showed an increase in water content of > 54% compared to the virgin membrane. The sodium sulfate salt rejection was measured > 70% for the bi-layer modified membrane. The chromium rejection increased from 69% for the virgin membrane to > 95% for the modified bi-layer membrane. The water contact angle results exhibited that the surface hydrophilicity of the membrane increased with the surface modification. The modified membranes showed superior antifouling ability as the flux recovery ratio increased from 85% to 93.6% and the irreversible resistance decreased considerably to 6.4%.

Hypothesis:

 In recent years, scientists and researchers have been looking for new and advanced materials for use in various fields, including drug delivery and biotechnology. One of the attractive  materials that has been considered in this field is chitosan-based bionanocomposite hydrogel beads. Chitosan-based bionanocomposite hydrogel beads have attracted attention as carriers in drug delivery systems due to their inherent properties such as excellent biocompatibility, high swelling, and high storage capacities.

First graphene quantum dots (GQDs) were prepared by the pyrolysis method, and then their magnetic properties were obtained using iron nanoparticles (MGQD). Next they were coated with chitosan hydrogel (CS-MGQD) and finally loaded with methotrexate (MTX/CS-MGQD). This unique combination of the properties of chitosan hydrogel, the magnetic properties of graphene quantum dots, and the ability to adjust drug release has been able to create an important milestone in the field of drug delivery research and the compatibility of drugs with the biological environment. Through various analyses, including FTIR to analyze the spectra of the functional groups, XRD to identify the crystal structure, and SEM to examine the morphology of the samples, the success of the synthesis and formation of the desired compound was confirmed.

The fabricated CS and CS-MGQD hydrogel beads were loaded with about 84% and 64% MTX, respectively. The results of the swelling behavior and drug release behavior showed that the hydrogel beads experience pH-dependent swelling and release of MTX. In addition, investigating the effect of MGQD concentration on swelling behavior and drug release showed that CS-MGQD has favorable stability and controllable drug release in an acid environment. Also, the Weibull kinetic model was found to be the best-fitting model for the release of MTX from CS-MGQD at pH 5. These findings suggest that the prepared magnetic bionanocomposite hydrogel beads have a good potential for pH-sensitive implantable drug delivery in the treatment of cancerous tissue.

Hypothesis: 

Considering water quality problems and strict rules established for drinking water treatment, there is an urgent need to use more effective and economical methods to remove natural organic matter from water. Meanwhile, membrane processes are one of the effective methods to remove these pollutants. In this way, in order to prepare a membrane with a high ability to remove pollutants, in the present study, the production and optimization of poly(vinyl chloride) (PVC) membranes with poly(ethylene glycol) (PEG) additives have been carried out.

PVC microporous membranes were prepared by nonsolvent-induced phase separation method. Influential parameters in the membrane fabrication, including the concentration of PVC and PEG and the composition of the coagulation bath were optimized using the response surface methodology (RSM). Meanwhile, tensile strength and porosity were considered as responses.

The obtained results showed that all the membranes had an asymmetric structure with finger like pores. It was also found that the tensile strength of the membranes increased with the increase in PVC concentration. The lowest tensile strength was related to the membrane made of 10.30% (by wt) of PVC, while the membrane made of 18.7 % (by wt) of PVC had the highest tensile strength. In addition, for the optimum membrane in which the concentration of PVC was 17.52% (by wt), the concentration of PEG was 5.87% (by wt) and the volume fraction of ethanol in the coagulation bath was 0.27, the tensile strength and porosity of the membranes were obtained as 5 MPa and 80.57, respectively. Furthermore, in the following, titanium dioxide nanoparticles (TiO2) were used to prepare the composite membrane under the aforementioned optimum conditions. The obtained results showed that the optimum membrane containing 2% (by wt) of nanoparticles had the highest humic acid separation efficiency with a value of 80%.

Hypothesis: 

One of the existing challenges in the foam production industry is to achieve the desired mechanical and thermal insulation properties required, which are directly related to cellular density, size, and distribution of bubbles. Therefore, predicting the bubble size distribution in each foam production system significantly contributes to the final properties of the desired foam. Nucleation, growth, coalescence of bubbles, and their final stabilization are influential stages in the ultimate properties of the foam that should be considered in predicting the bubble size distribution and laboratory testing phase.

Initially, a modified classical nucleation model was used for predicting cell nucleation, and then a population balance model was employed to predict the size distribution of bubbles in a batch system for the production of polystyrene foam. The modeling of this process was one-dimensional, and changes in bubble diameter were included as the characteristic variable of the system's equations. The foam production stage was carried out at temperatures of 70°C, 90°C, and 110°C, under a pressure of 20 MPa, and the consolidation stage was performed within 0.1 s and 1 s and without consolidation. To calculate the average cell size and size distribution, SEM images and software tools such as Axiovision.v4.82.SP2 and SPSS 26 were used, and the results were compared with the modeling outcomes.

Using the bubble size distribution obtained from modeling, the average bubble size at a saturation temperature of 70°C and a consolidation time of 1 s was 4.3 µm. With an increase in temperature from 70°C to 90°C, the average bubble size increased to 36.7 µm due to the higher rate of gas diffusion into the bubbles. With an increase in the amount of gas in polystyrene, the free volume increased, and glass transition temperature decreased. At 110°C, the average size of bubble cells increased to 78.1 µm. Since this temperature was higher than the glass transition temperature of polystyrene, in addition to the high gas diffusion rate into the bubble cells, the growth process did not stop, and gas diffusion and coalescence between the bubbles continued. Finally, the model predictions were compared with experiments under various conditions and demonstrated acceptable agreement.