فصلنامه بسپارش
سال سیزدهم شماره 3 (پیاپی 48، پاییز 1402)

Three dimensional printing (3D) is a process of fabricating 3D objects through depositing layers of materials (such as polymers) on previous layers. Currently is considered one of the most important research fields in academic and industrial research centers. Among the various approaches to 3D printing, photopolymerization is of great interest due to the wide range of monomers/oligomers prone to photopolymerization reactions (photopolymers). Photoinitiators and monomers/oligomers are two important components of resins applied for 3D process, which affect not only the possibility of resin printing, but also the functional properties of the part such as mechanical strength, dimensional accuracy, transparency, modulus and others. In this article, the most important group of photopolymers used in the 3D printing process is reviewed from the point of view of reaction chemistry and their advantages and disadvantages. It is obvious that the design and manufacture of photocurable resins requires knowledge about the types of resins available and the challenges associated with them. Therefore, this article can be a good source for active researchers in this field.

Cellulose is the main constituent of most plants. The renewability of this material has made it a natural raw material which is abundantly available and there is no need to worry about running out of its resources. However, the industrial application of cellulose as a thermoplastic polymer is associated with some problems and difficulties. Due to the presence of strong hydrogen bonds between its chains, cellulose is destroyed before melting. In order to eliminate such difficulties, researchers have developed celluloses derivatives. Ethyl cellulose is one of the most widely used polymers derived from cellulose. Today, cellulose derivative polymers, such as ethyl cellulose in particular, are widely used in numerous industries like ceramic manufacturing, cosmetics, pharmaceuticals, tobacco, paint, paper, food, textile, various molding parts and printing ink. Renewability, biocompatibility, and in some cases the biodegradability of this polymer along with its high tensile strength and appropriate toughness, make this polymer play a prominent role in polymer science and technology in the future. In this article, along with the introduction of ethyl cellulose, its various properties and characteristics, the different applications of this polymer's mixtures have also been reviewed.

Today, the presence of heavy metal ions in the wastewater of various industries is one of the environmental problems of the modern world. Therefore, various methods are used to adsorb and remove heavy metal ions from industrial wastewaters and effluents. One of the effective methods in this field is adsorption by polymer gels, which are divided into different categories including  hydrogels, aerogels, microgels and nanogels. These materials are porous cross-linked polymer networks. Having desirable physical and chemical properties such as high surface area, size variety, high durability, variety of solubility, active adsorption centers, and environmental compatibility, they can absorb heavy metal ions such as lead, cadmium, mercury and copper physically and chemically from contaminated aquatic environments without causing secondary destructive effects with high efficiency. The general structure of these gels is similar to each other, and factors such as pore size, mesh size, and the presence of liquid or gas in the pores create different categories. In this article, each types of gels and their unique properties are introduced first, then the general synthesis methods, special optimizations to enhance the adsorption and mechanisms of metal adsorption by gels are reviewed.

Silk is a natural fiber composed of proteins produced by some insects. Spiders produce protein macromolecules with different molecular structures for different applications. Spider web or other large protein structures are produced by the release of protein fibers from the spinning glands inside the spider's body, which act as a spinning instrument. Spider natural silk has received a lot of attention, due to its unique mechanical and physical properties, thermal resistance, biocompatibility, and biodegradability. These exceptional properties have led to the potential applications of spider silk fibers in production of bulletproof vest, artificial vessels, sensors, and etc. This interesting mechanical and physicochemical properties are due to the macromolecular structure of protein molecules as well as physical interactions between protein chains. derived from protein macromolecule’s structure, including the large protein sequences of the repeating units as well as physical interactions between protein chains and specific mechanisms such as tension, pH adjusting, and ion exchange in spinnerets of spider. Due to the remarkable difficulties in natural production of spider silk, other advanced techniques like inserting spider DNA in animals or bacteria is employed, but fibers produced by these methods do not have mechanical and physicochemical properties of natural spider silk lower molecular weight of the protein chains. Spider silk fibers have potential applications in pharmaceutical and military industries and this study can open a new window to the future of these fibers.

In this study, foaming process of polyvinyl alcohol with the addition of some compounds was investigated using the batch foaming technique. The reason for the crystalline structure in polyvinyl alcohol is presence of strong hydrogen bonds between its chains. By adding some plasticizers and additives, these strong bonds can be broken and new bonds can be formed. Studies show that the foamability of semi-crystalline polyvinyl alcohol biopolymer was improved significantly after adding softener and nanoparticles as nucleating agent. Various analyzes showed that suitable intermolecular interactions occur in polyvinyl alcohol and its blends in turn expand the processability window of polyvinyl alcohol. Polyvinyl alcohol is a very suitable option for tissue engineering applications due to its non-toxicity and high biocompatibility. Considering this case, it is very important to examine the morphology of the produced sponges using a scanning electron microscope and study the cell structures of the resulting foam. It was found that by changing the operational variables and adding different polymer compounds, a significant change in the structure and cell density of polymer foams was observed. Also, the cell size distribution, cell density and porosity of the produced foams can be controlled by adding certain amount of additives and changing pressure and temperature.

The production of stone paper as a product with unique characteristics such as waterproofness, resistance to bursting and appropriate rupture, as well as due to the reduction of water consumption, energy and greenhouse gas emissions during the production process, is expanding. In this article, the characteristics, production process, applications, development process and general comparison of stone paper with paper are reviewed. Due to its advantages such as very low water absorption, good printability and lower cost, this product has been proposed as a competitive product with conventional cellulose papers in the packaging, printing and publishing industries, especially labels. However, due to the different structure of paper, mixing with it can cause problems in the normal paper recycling cycle. Higher density, lower tensile strength, degradability under sunlight and ultraviolet light and the presence of polyethylene, are the main disadvantages of stone paper, which poses challenges in the application of this product. Paper stone recycling and using biodegradable polymers and UV-resistant additives and arrangements to separate it from recycled paper, will provides the possibility to replace it with some more paper products. Knowing the appropriate applications of this new product and the target markets, considering the reasonable price of its raw materials and availability in Iran and unique features of this product seems essential. The justification and success of new investments in the production of stone papers from the economic, technical, marketing and environmental terms is due to the knowledge that it reduces the risk of wasting the country's capital and problems in the paper recycling industry.