Sharif Digital Repository

Epoxy resins are relatively brittle and have low resistance to crack propagation. It is common to add rubber particles to improve crack resistance in epoxies, although these particles may deteriorate the strength of the matrix. Different nanomaterials are used to overcome the inherent brittleness of epoxies and to keep the mechanical properties. Among them, carbon nanotubes has been attracted many attentions. Fractue behavior and mechanical properties of two kind of novel nanocomposites, i.e, epoxy/carbon nanotube and epoxy/rubber/carbon nanotube are investigated in current study. Electron microscopy investigations were done to assure the CNTs distribution and fracture mechanisms as well.... 

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.... 

Because of increasing usage of modified polymers and consequent necessity for investigation and modeling of mechanical behavior of these materials, it is important to get a yield criterion for these materials. For this purpose the Gurson yield criterion presented for porous metals, was modified with regard to mechanical properties of polymers. Indeed pressure sensitivity of polymers and their large elastic strain during deformation, makes using of Gurson yield criterion problematic for modified polymers.
For modification of Gurson criterion, macroscopic hydrostatic yield stress equation was derived for a thick-walled spherical shell of epoxy and then Gurson criterion was modified with... 

In recent years, it has been interesting to to use nanodiamond (ND) in oreder to improve mechanical and electrical properties. Producing it in very low dimensions, make it more important to treat ND surface proportional to its application. Hence, with knowledge of influence of ND and its functional groups on curing process, in present research,carboxylic acid and amine were settled on its surface and in addition to untreated ND, they were dispersed in DGEBA epoxy as a reinforcement. Afterward, by adding triethylenetetramine kinetic cure of nanocomposites were investigated. For this purpose, conversion was determined using heat flow of reaction and then activation energy was calculated.... 

Plants and aquatic creatures growth on the surface of human made structures is a typical phenomena. One of the approaches to prevent algae and moss to grow is using paint coatings including biocides. In this research project, anti-moss paints containing Copper Oxide as the major biocide and Zinc Oxide as the minor biocide have been synthesized. The effects of different parameters like the type of resin, biocide concentration, biocide grain sizes, dip time, and the coating layer thickness on the release rate which is the most important factor to prevent moss growth, have been investigated. Then, the experiment has been conducted on the specimens in algae growth and flustered sea water... 

With increasing awareness, artificial materials have been replaced by recyclable materials and green materials. In the manufacture of composites, natural and degradable materials are also used. The main object of this research is the fabrication of natural fiber reinforced composites. In this research, fibers are used that are cultivated in the country. Also, the effect of fiber length, fiber mass percentage and fiber correction on composite properties was investigated. The fiber length factor is at two levels of 5 mm and 9 mm, the percentage of fiber mass is in four levels of 5%, 10%, 12.5% and 15%, and the factor for correction of fibers is also in two groups of modified fibers and... 

In the first stage of this research, different amounts of glycidoxypropyltrimethoxysilane (GPS) were grafted as a coupling agent on the surface of nanosilica particles (NS). Surface characterization was done by Particle Size Analyzer and Thermal Gravimetric Analyzer (TGA) and that way, samples were distinguished from each other. More comparisons were taken by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). Then the different amounts of modified NS were added into the matrix of an epoxy resin and the physical and mechanical properties of samples were tested with Abrasion Resistance test, Tensile Strength test, Thermal Mechanical Analysis (TMA),... 

Nowdays, one of the most important concerns for scientists is increasing CO2 emmisions and global warming. To overcome this problem, a large number of studies have been carried out to improve energy system performance and reducing the overall energy consumption. One solution to this problem is using the superhydrophobic surfaces with contact angle larger than 150°.In this study, we try to reduce the pressure drop through the galvanized pipes. So, by reducing the pressure drop, power required for pumps can be reduced. To this end, two different coatings by silica nano-particles which were modified with first hydrophobic agent are used. In first coating which is named as PS coating, stearic... 

Nowadays, self-healing process, repairing minor damages automatically without the need for detection or any type of manual intervention, becomes a hot topic of general interest. In this research, the effect of addition of carbon nanocontainers doped with film forming epoxy and polyamine agents in various contents on the self-healing properties of epoxy resin was investigated. Carbon nanocontainers were synthesized via the silica templating method and carbonization of polysaccharide shells at the high temperature. Loading of the film forming agents into carbon nanocontainers was performed using vacuum jar method in the presence of epoxy/acetone and polyamine/acetone dilute solutions.... 

This study investigated the effect of oxidized molybdenum disulfide (MoS2) nanosheets on the anti-corrosion and rheological properties of epoxy resin. Raw MoS2 sheets were obtained as layered nanosheets with a thickness of 50 to 100 nm using acid washing, oxidation, and heat shock methods. The use of nanoparticle characterization tests such as XRD, FT-IR, FE-SEM, EDS, and TGA supports this claim. Then, in the next step, epoxy coatings containing different percentages (0, 0.3, 0.5, 0.8, and 1.5 wt%) of MoS2 nanosheets were prepared with polyamide hardener to investigate the effect of adding nanosheets and the optimal percentage. The best effect on the corrosion properties of the coating in a... 

Polymer composites, due to its exclusive properties, has a special place in industry. Epoxy resin with high adhesion property, low density, thermal stability and high chemical resistance has a special place as matrix in fabrication of high technology hybrid composites. Hybrid composites, due to its high strength and long fatigue life, used to reinforcing building structures and manufacturing fuselage. Layer and reactive structure near the firm core and wear-resistant of NDs, used to improvement of epoxy reisn and hybrid NanoComposite interphase properties. In this study, for improvement of the properties of hybrid NanoComposites, used the NDs in 0.25, 0.5 and 1 %wt with amine and carboxyl... 

Nowadays, composites have wide applications in different industries especially in aerospace industry because of their high strength to weight ratio. Epoxy 5052 for its relatively good mechanical properties and high thermal resistance has vaidly use for manufacturing of large composite components. However; fracture toghness of epoxy resins is not good in comparison to their other exceptional properties. Therefore, researchers have endeavored to improve this characteristic with different approaches. One of these methods is nanotechnology. Since the components in aerospace industry are often under impact loads and impact strength of these materials has been less studied, effect of carbon... 

Due to population growth, the demand for water supply has increased. This need has drawn attention to the use of consumed and treatable water resources. Organic pollutants are a key source of water pollution. On the other hand, petrochemical oil pollution and frequent oil accidents during oil production or maritime transport have become one of the environmental problems.There are different methods for water and oil separation and water purification that in the present project, selective separation can be achieved by using hydrophobic materials and surface roughness and creating surfaces with two properties: superhydrophobic and ultra-oil friendly. This method is also very effective, cheap... 

To protect mild steel against corrosion, an intelligent self-healing epoxy (EP) coating including carbon nanofiber (CNF) modified with polydopamine (PDA)-La (III) complex was successfully fabricated. The high aspect ratio and unique thermal and electrical characteristics of CNF made it an ideal physical barrier against the penetration of corrosive ions. Due to the poor dispersion of CNF, its surface was modified using PDA. PDA, which contains functional groups such as catechol, amine, and imine, can mitigate corrosion reaction by generating the Fe-Catechol complex and also boost the coating's adherence to the metal surface, in addition to anchoring La3+ inorganic corrosion inhibitor....