مجله پژوهش و توسعه فناوری پلیمر ایران
سال هشتم شماره 2 (پیاپی 30، تابستان 1402)

The demand for rare earth elements has increased significantly due to potential industrial applications such as catalysts, magnets, battery alloys, ceramics. However, the separation and recovery of rare earth metals are very difficult due to their similar chemical properties and ionic radius, so progress in the separation process of these elements will bring many global benefits. Among the improved methods, the membrane technique has received much attention as a stable method with easy operation in the separation of such metals, and several membranes have been designed for separation. This article provides a summary of the types of membranes in the separation of rare earth elements in terms of extraction performance, transfer efficiency, and membrane stability. Polymer inclusion membranes are a new generation of non-liquid membrane that is made by a simple method of casting a solution containing liquid phases (carrier, plasticizer /modifier) and base polymers. Polymer inclusion membranes due to the possibility of simultaneous extraction and back-extraction, high selectivity, excellent stability, reusability, simple applicability, relatively low cost, and low energy consumption, it provides a great advantage in both the separation and purification of metal ions. Therefore, in this study, an overview of the PIMs reported in the studies to date is presented and the performance, permeability and stability of the membrane are discussed according to the base polymer, carrier, plasticizer and modifiers used.

Waste tires are the main source of waste rubbers. Their recycling raises environmental concerns due to the high volume of production as well as a very crosslinked and non-biodegradable structure. This leads to finding easy, low-cost, and energy-efficient methods for recycling waste tires. To now, many studies have been devoted to the improvement of conventional recycling methods and the introduction of new ones for the management of waste tires. Methods for recycling waste tires include retreading, incineration, pyrolysis, and grinding. The lifetime of a tire can be extended using the retreading process, in which the old tread is removed and a new one is inserted. The produced energy from the incineration of the waste tire can be used as a fuel source for steam, electrical energy, paper paste, paper, lime, and steel production. In the pyrolysis process, oil, gas, and char are produced through thermal decomposition. The main method of waste tire recycling is grinding for the incorporation of produced particles in the polymer matrices. The ambient and cryogenic grinding are the most conventional methods for grinding waste tires. The size reduction results in a higher specific area and better distribution of rubber particles in the matrix. The produced particles can be used as fillers in asphalt, concrete and glassy polymers.

Hydrogels are three-dimensional networks of hydrophilic polymers capable of absorbing and retaining significant amounts of fluids, which are also widely applied in wound healing, cartilage tissue engineering, bone tissue engineering, release of proteins, growth factors, and antibiotics. In the past decades, a lot of research has been done to accelerate wound healing. Hydrogel-based scaffolds have been a recurring solution in both cases, although their mechanical stability remains a challenge, some of which have already reached the market. To overcome this limitation, the reinforcement of hydrogels with fibers has been investigated. The structural similarity of hydrogel fiber composites to natural tissues has been a driving force for the optimization and exploration of these systems in biomedicine. Indeed, the combination of hydrogel formation techniques and fiber spinning methods has been very important in the development of scaffold systems with improved mechanical strength and medicinal properties. Hydrogel has the ability to absorb secretions and maintain moisture balance in the wound. In turn, the fibers follow the structure of the extracellular matrix (ECM). The combination of these two structures (fiber and hydrogel ) in a scaffold is expected to facilitate healing by creating a suitable environment by identifying and connecting cells with the moist and breathing space required for healthy tissue formation. Modifying the surface of fibers by physical and chemical methods improves the performance of hydrogel composites containing

The scope of application of elastomers is largely due to their ability to be combined with a large number of chemicals and additives such as softening aids, vulcanizing chemicals, aging protectors, fillers, softeners, sponging agents and so on. Basically, the nature of an elastomer determines the main properties of the product from which the elastomer is prepared, but these properties can be significantly changed by using the types of materials mentioned above and their different amounts in the product formula. On the other hand, chemicals and fillers affect the behavior of elastomeric mixtures during mixing and processing and make their vulcanization possible, also, they make it possible to change the properties of vulcanized mixtures on a large scale and use them in many applications. A mixologist often uses all the opportunities and facilities available to him in order to more easily achieve to the desired characteristics in a mixture. Achieving these characteristics requires a high level of knowledge about chemicals and additives used in the preparation of a compound. Considering the importance of chemicals in the rubber industry, in this article we tried to describe comprehensively the types of chemicals needed to make rubber, including rubbers, fillers, softeners, activators, antioxidants, curing agents and process aids.

Tissue engineering is a science that uses the combination of scaffolds, cells and active biomolecules to make a tissue in order to restore or maintain the function and improve the damaged tissue or even an organ in the laboratory. Artificial skin and cartilage are among the engineered tissues that have been approved by the US Food and Drug Administration (FDA) for clinical use. Accuracy in the design and fabrication of scaffolds with ideal properties such as biocompatibility, biodegradability, mechanical and surface properties is very important for applications in tissue engineering. Furthermore, these techniques should be able to translate the fabricated scaffolds from potential to actual applications. Several fabrication technologies have been used to design ideal 3D scaffolds with controlled nano- and micro-structures to achieve the ultimate biological response. This review highlights the applications and ideal parameters (biological, mechanical and biodegradability) of scaffolds for various biomedical and tissue engineering applications. This review discusses in detail the various design methods developed and used to design scaffolds, namely solvent casting/particle leaching, freeze drying, thermally induced phase separation (TIPS), gas foaming. (GF), powder foam, sol-gel, electrospinning, stereolithography (SLA), fused deposition modeling (FDM), selective laser sintering (SLS), jet binder technique, inkjet printing, laser-assisted bioprinting, writing It reviews direct cell and metal-based additive manufacturing, focusing on their advantages, limitations, and applications in tissue engineering.

The presence of heavy metal ions in polluted wastewater represents a serious threat to human health, making proper disposal extremely important. The utilization of nanofiltration (NF) membranes has emerged as one of the most effective methods of heavy metal ion removal from wastewater due to their efficient operation, adaptable design, and affordability. NF membranes created from advanced materials are becoming increasingly popular due to their ability to depollute wastewater in a variety of circumstances. Tailoring the NF membrane’s properties to efficiently remove heavy metal ions from wastewater, interfacial polymerization, and grafting techniques, along with the addition of nano-fillers, have proven to be the most effective modification methods. This paper presents a review of the modification processes and NF membrane performances for the removal of heavy metals from wastewater, as well as the application of these membranes for heavy metal ion wastewater treatment. Very high treatment efficiencies, such as 99.90%, have been achieved using membranes composed of polyvinyl amine (PVAM) and glutaraldehyde (GA) for Cr3+ removal from wastewater. However, nanofiltration membranes have certain drawbacks, such as fouling of the NF However, nanofiltration membranes have certain drawbacks, such as fouling of the NF membrane. Repeated cleaning of the membrane influences its lifetime. membrane. Repeated cleaning of the membrane influences its lifetime.