Sharif Digital Repository

In this study, polyethylene films made of LDPE / LLPE / reinforced with mechanical barrier of clay and reactant of iron nanoparticles were made in their optimal combination and necessary improvements were made on them. Investigations show that, independent of volume fraction, the addition of spherical nanoparticles does not have much effect on reducing the polymer matrix’s permeability. In nanocomposites containing cylindrical particles, for considerable reduction of the permeability, over 20 volume percent of nanoparticles it is required, while in platelet nanoparticles, less than 10% vol is sufficient. In clays with modifier concentration above the cation exchange capacity, there is less... 

Concrete-filled GFRP and PE tubes are composite systems using the polymeric tubes as confinement for the marine structures to extend their service life. However, elevated temperatures and thermal cycles in marine environments can affect the behavior of such composite systems. In this investigation, the effect of elevated temperatures and thermal cycles on the performance of concrete-filled pultruded GFRP tubes (CFPGT) and concrete-filled polyethylene tubes (CFPT) is assessed, respectively. For this, different parameters such as concrete core strength (30 and 60 MPa), exposure temperature (25, 100, 200, 300, and 400°C), time exposure (60 and 120 min.), number of thermal cycles (50, 100, and... 

In this study the behavior of buried pipes under permanent ground deformation (PGD) ef-fects caused by reverse faulting is investigated by means of both experimental and numeri-cal approaches. A total number of 7 full-scale experiments on buried steel pipes subjected to a fault offset of 0.6 m along the slip plane is carried out and the effects of different pa-rameters such as pipe diameter (114.3 mm (4ʺ) and 168.3 mm (6ʺ)), burial depth (0.25m, 0.5m, 1 m) and soil type (SW and SM) on the response of the buried pipes are studied. Ex-perimental results show that the pipe deformation shape changes with increasing burial depth from half-sine (for shallow depths) to an S-shape (for moderate to... 

Vortex flow is one of the most sophisticated fluid movements in nature which has great industrial and scientific importance. In this dissertation, in order to study the combustion process due to a vortex flow, a new experimental model of a cold wall vortex engine, was designed, fabricated and tested with oxidizer issuing tangentially toward the end of the chamber. The cold wall effect in these chambers is a result of the cool layer of oxidizer which significantly reduces the amount of heat transfer to the chamber’s wall. This experimental model was designed to withstand the massive temperature rise resulting from the usage of Polyethylene as fuel and Nitrous oxide as oxidizer. In a series of... 

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... 

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... 

Nowadays, with the increasing number of polyethylene terephthalate wastes, the issue of its recycling has become very important. Among the problems of polyethylene terephthalate recycling are its loss of crystallinity and mechanical properties. Recycled polyethylene terephthalate does not have the properties of new polyethylene terephthalate and using its mixture with other materials is an effective way to remove its waste from nature and return it to the production cycle. The aim of this study is to produce a mixture of recycled polyethylene terephthalate with polycarbonate and glass fibers with mechanical properties such as good impact strength, which ultimately leads to the production of... 

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... 

In this research, a polyethylene / thermoplastic film containing ethylene adsorbent nanostructure was fabricated to package agricultural products and increase the shelf life of fruits and vegetables. The thermoplastic starch containing 60 wt% starch and 40 wt% plasticizers with weight ratios of 5: 1, 4: 1, and 3: 1 sorbitol to glycerol was added to the polyethylene film to determine the composition of the final film. The film was prepared by a combination of low-density polyethylene with 10wt % linear low-density polyethylene, 30 wt% thermoplastic starch (4: 1 sorbitol to glycerol ratio), and 3wt% PE-g-MA as compatibilizer. Then, halloysite nanotubes were added to the film as ethylene... 

The use of polymers is increasing day by day due to low density, reasonable price and ability to produce different products. On the other hand, the accumulation of polymer wastes in nature is one of the environmental concerns in today's world, which is mainly due to the widespread use of polymers in the packaging industry and disposable applications. In order to solve this problem, recycling is recommended as the most appropriate and economical solution. Because in addition to consuming polymer waste, it also saves energy and reduces carbon footprint.Polyethylene terephthalate (PET) is one of the polymeric materials which; It has a special place in the packaging industry and is widely used... 

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... 

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... 

Medical engineering advances in total joint replacements and society’s rising demand for long lasting materials, have proven it essential to manufacture materials that are more similar to the original tissue in the fields of mechanical, tribological and biological properties. Ultra High Molecular Weight Polyethylene(UHMWPE), is a polymer widely used in arthroplasty applications due to its biocompatibility, chemical stability and proper mechanical properties. In this study, UHMWPE-HAp nanocomposites reinforced with Zirconia and Graphene were manufactured aiming to reach a structure that is more compatible with bone tissue and also to improve overall properties. First, using ultrasonication... 

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... 

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... 

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 this study, antistatic waterborne polyurethane coating containing zirconia nanoparticles is made and applied on 304 stainless steel substrates at weight percentage of 0.66, 1.3, 3, 4.5 and 6% zirconia nanoparticles. For synthesis of hydrophilic isocyanate prepolymer, isocyanate prepolymer is modified by hydrophilic polyethylene glycol with molecular weight 600, 1000 and 4000. For ensuring of modification condition and stability of hydrophilic isocyanate prepolymer in aqua solution, FTIR and stability tests are employed, respectively. In order to create antistatic properties of these coatings, semi - conductive zirconia nanoparticles are used. To improve the distribution of zirconia... 

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... 

Recently, due to the increase of environmental concerns, a significant raise in applying films and packaging containers, pollution produced from petroleum-based plastics packaging and problems arising from the various methods of waste disposal, the researchers have concentrate to replace these materials with biodegradable ones. In this study, a nanocomposite based on alloy matrix of thermoplastic starch and polyethylene which is reinforced with different amounts of Montmorillonitenanoclay has been constructed by the extrusion process. Furthermore, in order to increase the compatibility between the polar and non-polar components in the group of samples, compatibilizer was used and its...