Sharif Digital Repository

Nowadays filtration process is increasingly used in various areas such as water purification, food industries, filtering the air dust and other separation applications. In this work, the HDPE microporous filters have been fabricated at different temperature, pressure and time conditions via sintering process and then were characterized by different techniques. It can be expected that microstructure and mechanical properties of the samples could be controlled by changing the fabrication parameters of the process and also by changing the properties of the resin such as powder shape, particle size and rheological properties. In the first step, by using DSC, MFI, rheology test and optical... 

In Lithium ion batteries, the separator is membrane that placed between the cathode and the anode is one of critical components. Its primary function is to effectively transport ionic charge carriers between two electrodes as an efficient ionic conductor as well as to prevent the electric contact between them as a good electric insulator. The separator does not involve directly in any cell reactions, but its structure and properties play an important role in determining the battery performance. Commercially available polyolefin separators low cost, good electric resistance, high electrochemical stability, and effectively prevent thermal runaway caused by the electrical short-circuits or... 

To reduce material consumption needed in production as well as avoiding thousands of tons of contaminations produced by spent materials in the battery industry, recycling was taken into consideration. In this study silica was recycled from spent lead-acid battery separators by the pyrolysis process. silica along with high-density polyethylene (HDPE), can be used as supporting material for fabricating form-stable phase change materials (FSPCM). FSPCMs are of great ability to be used as thermal energy storage (TES) in different parts of a building e. g. wallboards to reduce energy consumption. In this line, an eutectic mixture of lauric acid, palmitic acid and paraffin with the melting point... 

In this project, all-cellulose nanocomposites for smart packaging of meat products were synthesized via film casing method. These nanocomposites were aimed to provide visual response to pH change, which occurs due to decay of the meat products. The prepared nanocomposites would be placed inside the packages to be in direct contact with the products and could improve shelf life the products with the help of antibacterial natural extracts incorporated in the samples.Synthesis of the samples started with cellulose nano whiskers synthesis via acid hydrolysis. The prepared nanoparticles were then characterized with XRD, DLS, and Zeta potential analysis. It was shown that a big portion of the... 

Graphene is two dimensional nanomaterial, single layer of carbon atoms that exhibited excellent properties like high electrical conductivity and stiffness, but producing graphene and obtaining a good dispersion of graphene in a polymer matrix is still a major challenge. In this study by using the electrochemical route several graphene with different degree of oxidation produced in different electrolyte medium. According to XRD data, product of electrochemical exfoliation in dilute HNO3 medium includes 50% few-layer graphene (5 layers) and 25% GO and the rest are multi-layer graphene. Nonsolvent induced phase separation method were used to prepare TPU/Graphene nanocomposite. Different methods... 

Polymeric film for packaging applications are commonly made from a variety of polyethylenes using a blown film process. Nowadays high density polyethylene with bimodal molecular weight distributions are used to improve the performance and the final properties. In the present study samples with different bimodal molecular weight distribution in a similar film preparation are developed. The EX5 sample from the Jam Petrochemical showed microstructure with heavily oriented stack of lamellae in the machine direction. In contrast, the 7000F sample from the Mehr Petrochemical presented a microstructure with a lower degree of lamellae, containing lamella twist and more link between the crystalline... 

Recently, macroporous polymers have gained wide acceptance for applications such as filters, membranes, biodegradable scaffolds, retention media, sound mufflers and etc. In this research, by keeping in mind the importance of the pore structure in the functionality of the porous part, three dimensional images of the pore structure during sintering was obtained using an optimized manual serial sectioning technique. Then, using the Euler number as a property of the topology of the pore surface, evolution of the three dimensional pore structure was scrutinized for two types of powders, powder A with a mean particle size of 200 micron and melt flow index of 0.2 (g/10 min) and powder B with a mean... 

In recent years, Jam Petrochemical has produced and designed irrigation tape polyethylene grades but because these grades don’t have sufficient melt strength during high-speed processing, it hasn’t been welcomed by manufacturers. Therefore, in first step of this study we tried to characterize the specimens by using referenced grade and by taking advantages of thermal, rheological and mechanical analysis. We observed that main difference between jam petrochemical grades and referenced grade is related to type and content of comonomer and also long chain branches. Based on the obtained results, the ideal molecular structure of irrigation tape grade, include chains with bimodal distribution... 

Polyethylene is the most widely used plastic material in the world for reasons such as lightweight, good strength, good processability, low cost, and low maintenance cost, and very good chemical resistance. One of the applications of polyethylene that has received much attention in recent decades is its use in the manufacture of hot water pipes. To maintain the properties of polyethylene at high temperatures, it must be crosslinked at a proper level. Appropriate antioxidants should be used to prevent the degradation and oxidation of polyethylene during the process as well as long-term operation. Concomitant use of phenolic antioxidants for long-term stability during service and phosphorus... 

Creating sustainable development in today's human societies is essential, one of the pillars of achieving this important goal is environmental protection. Thus, waste management as a new challenge is leading engineers. Lead-acid battery waste is one of the sources of environmental pollution. Lead-acid battery separators contain 50% recyclable nanosilica. The main challenge of recycling nanosilica from separators is the presence of significant amounts of 6 to 9% wt.% of lead and 5% by weight of other impurities. Therefore, in the present study, lead trapped in the separating pores is removed using mechanical washing or abrasive washing. Then, the quality of recycled nanosilica is evaluated... 

PE pipes and specially PE100 are commonly used for the transportation of drinking water, transferred water was mostly disinfected by disinfectants such as chlorine, chlorine dioxide and chloramine. Long-term contact with water containing disinfectants led to morphological and mechanical changes and followed by oxidative degradation and failure. Antioxidants are stabilizers which are used in PE pipes to postpone oxidation and increase the durability of these pipes. Migration of antioxidants is possible during the terms of service, in this case antioxidants can be washed by water and left the pipe. As a result, the loss of antioxidants decreases the stability of pipes and leads to oxidative... 

Polyethylene is one of the most widely used polymers for the production of drinking water pipes. The presence of chlorine-based disinfectants in drinking water leads to long-term chemical destruction of pipes and sometimes reduces the life of pipes by half. Therefore, it is very important to investigate various factors affecting the chemical resistance of polyethylene pipes. The crystalline microstructure of the substance is affected by the average molecular weight, type and distribution comonomer on the chain, is one of the important and influential factors on the chemical resistance of these species against chlorine dioxide as a disinfectant. In this research, the chemical resistance of... 

Polyethylene is one of the most widely used industrial materials for producing water and gas pipes due to low pricing and mechanical properties and high corrosion resistance. Various parameters such as molecular weight and the short chain branches distribution strongly affect the mechanical properties of these materials. PE100 grade of this material has been introduced with bimodal molecular weight distribution, has excellent mechanical properties and especially high creep resistance and today is used for pipe production in water distribution systems. In the first part of this study, the effect of 1-butene comonomers on different properties of three PE100 and two PE80 resins produced in... 

Polyethylene, due to its low production and maintenance costs, light weight and excellent chemical resistance, is the most widely used material for production of water and gas transfer pipes. Pipe grade polyethylene (PE100) with bimodal molecular weight distribution has excellent mechanical properties, especially long-term creep performance. In order to prevent UV degradation, carbon black is added as masterbatch to PE100 to produce black compounds, which acts as most effective industrial UV stabilizer of polyethylene. Five PE100 black compounds and one white PE100 as reference sample were produced using a twin-screw extruder. Rheological, melt flow DSC, TGA, FE-SEM and tensile tests were... 

The World Health Organization's annual statistics show that 83% of wounds are caused by bacterial infections. Diabetic ulcers affect approximately 28 million people worldwide. The use of antibacterial dressings can help control infections. Recent studies have found that electrical stimulation can accelerate wound healing. However, there is still a need for interventions that speed up epithelial tissue formation. New dressings with zinc and silver particles that have electrical activity are being developed, but research on these methods is limited. Zinc oxide nanoparticles have been used as antibacterial agents due to their unique surface properties. This research aims to use these... 

Polypropylene is a semi-crystalline thermoplastic used in various industries and the second most used polymer globally. Polypropylene is sensitive to degradation by o agents due to having tertiary carbon in its chain. Chlorine-based disinfectants, used to disinfect drinking water, cause the degradation of hot water pipes made of polypropylene random copolymer. The stability of polypropylene against oxidizing chemical agents depends on the type of crystalline phase and polymer morphology. This research investigated the effect of alpha, beta, and gamma crystalline phases and spherulite size on random polypropylene copolymer's chemical stability in chlorine dioxide. Three samples were prepared,... 

Polycarbonate (PC) and polyethylene-terephthalate (PET) are important engineering thermoplastics. During last decades these polymers and their blends have been studied extensively due to their wide range of applications. Blends of PET and PC combine mechanical properties and chemical resistance together, which make applicable in various components such as automotive, electrical and of medical parts. It has been accepted that PET/PC immiscible blends are subjected to transesterification reactions during thermal processing, which produces PET-PC copolymer chains. In fact, scissioning and substitution of ester/carbonate functional groups of PC and PET at the interface, transforms the initial... 

Epoxy resins are used for a wide number of application due to good stiffness, chemical resistant and dimensional stability. This is the reason of their use as matrix in composite material. The incorporation of a small amount of carbon nanotubes (CNTs) in epoxy increases mechanical properties if nanocomposite have strong interfacial interaction between epoxy and CNTs, fine dispersion of CNTs and high final aspect ratio CNTs. In Noncovalent functionalization by polymer surfactant, CNTs are dispersed in a solvent/surfactant solution by ultra-sonication and then added to epoxy. In this thesis a novel study of toughening and mechanical properties of epoxy/ rubber/ CNT nanocomposite is presented.... 

Wound is a defect or failure in the skin texture which occurs as a result of physical or heat injuries or physiological conditions. The wound dress as a temporary cover can improve wound healing process and due to the unique properties, hydrogels have become appropriate choice for this application. Hydrogel’s structure allows drug to be loaded in the wound dress. Hydrogel wound dress should have adequate fluidity to cover wound’s bed and make full contact with the skin. Sufficient cohesion and strength is also necessary to allow the wound dress to remove from wound completely. Therefore, the study on the viscoelastic properties of hydrogel is important. In this study, polyvinyl alcohol... 

In the recent years, the enhancing of utilization of polymeric materials, especially in packaging application, became the serious concern because of the problems of their recycling. One of efficient ways for solving this problem is usage of biodegradable polymers. Thermoplastic starch (TPS) is one the alternative materials which is produced in gelatinization process by plasticizers. However, using of TPS because of its low mechanical properties, poor processability and high water absorption is not applicable and it is necessary to improve that. One of the strategy in order to improving the TPS properties is blending with other polymers, such as polylactic acid (PLA) which the biodegradable...