Sharif Digital Repository

Phenolic foam are common among the polymeric foams, they can be prepared from resole resin, it is possible to apply an external thermal reservoir to achieve curing and expansion simultaneously, or use an acid as curing agent, without external heating, and utilize heat of curing reaction for expansion of foaming mixture. Because of economic aspect of view and ease of processing the latter method is preferable. However, the existing problem is that the resole resin must be so active to react with acid curing agent and produce suitable heat. Also,physical properties of resin such as viscosity have a great importance to the efficiency of resin in foam processing.In the present work, resole... 

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.... 

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... 

Here, we have simulated isothermal vacuum assisted resin transfer moulding (VARTM) using a control volume/finite element scheme. Two dimensional and dimensional (shell geometries) spatial discretization is used. Resin motion through fibers is enforced by vacuum negative pressure in downstream. The governing equations are mass conservation and well known Darcy equation. Using an unstructured triangular grid, complex geometries could be modelled. Application of a quasi-steady algorithm results in a system of linear equation for pressure distribution. This system must be solved in each time step. The point successive over-relaxation (PSOR) scheme is used to solve the system of linear... 

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.... 

In this study, uranium removal from phosphoric acid with doulite resin was examined. Different uptake properties of the doulite resin were examined using batch, stirred and column methods. Langmuier, freundlich and dubinin equation was fitted the isotherm data and freundlich equation showed the best fitting. Adsorption kinetics was controlled by slow intraparticle diffusion of UO22+ ions in resin, and it obeyed a shrinking core model. Also a pseudo-second order chemical reaction fairly fitted the kinetics data  

The use of Vacuum Infusion Process (VIP) in some industries , to achieve optimal injection strategy is based on trial and error and it comes to the production of defective and unusable parts.The main problem is that no resin penetrate in some areas and creat dry spots and unsaturated resin regions Because of inadequate or incorrect positioning of the resin inlet and air outlet.Simulation is a powerful tool for understanding and identifying the behavior of resin flow and thereby save time and cost.In this research,in order to avoid the empirical testing of different injection techniques and avoid wasting time and cost in traditional methods of trial and error,the use of vacuum... 

The Visbreaking process is one of the Residue upgrading method, which, in addition to the production of mid-distillate products, also reduces the viscosity of feed. By reducing the viscosity of the feed, the amount of cutter stock is reduced to produce fuel oil. Since the refiners want to achieve the maximum conversion in the visbreaker unit, it is necessary to estimate the proper operating conditions and distribution of the products. Increasing in conversion in a visbreaker unit will lead to a refinancing profit. In this work, four Vacuum Residual oil from Iranian Refineries were selected for studying on visbreaking process. Experiments were carried out at RIPI-Petroleum Refining Technology... 

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... 

Ion exchange resins are widely used in nuclear industries. These spent resins result in the production of a large amount of low and intermediate level radioactive wastes, therefore, the treatment and immobilization of spent ion exchange resins are the major problems in the development of nuclear power plants.In this research, in a laboratory scale, we tried to find the suitable procedure and formulation to immobilize a specific group of cation-exchange resins which is used in Bushehr nuclear power plant (AMBERLITE IRN-97H) in the cement matrix. The solidification matrix consists of five constituents: anti sulfate slag type portland cement, cation-exchange resins, diatomite, sodium hydroxide... 

Polypropylene (PP) is one of the most widely used commercial plastics in various industrial applications due to its desirable physical and mechanical properties and low cost. Engineering properties of this polymer depend very much on its crystalline structure. It is a common practice in polymer industry to modify crystalline structure by means of nucleating agents. Since nucleating agents are added in a rather low level to polymers, some investigators have tried this task in modifying crystalline structure of polypropylene by incorporating nucleating agent masterbatches. However, none have looked at the possible influence of the carrier resin in such masterbatches on the performance of... 

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 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),... 

In the recent decade, composites have been used in safety system of automobiles due to important characteristics such as high wear resistant and durability, low weight and also low noise pollution, stable friction coefficient, availability and low cost. In recent years, composites have attracted the attention of brake pads manufacturers because of their appropriate thermal and mechanical properties. Fibers play an important role in these material. Carbon fiber due to its features such as high strength, acceptable module, proper heat transfer coefficient and excellent resistant against thermal degradation has been considered by the experts but there is not any comprehensive research on... 

Recently nanodiamond has drawn a vast attention of researchers due to exceptional mechanical properties. However, nanodiamond tendency to aggregation in polymer matrix restricts its reinforcement properties. In this research, novolac phenolic resin nanocomposites reinforced by nanodiamond were prepared by solution blending method and their mechanical properties were investigated. In order to prevent nanodiamond aggregation, ultrasonic treatment was used and nanodiamond surface was modified with acid and amine functional groups. FTIR and TGA were performed in order to investigate nanodiamond surface and confirmation of existence of acid carboxylic and oleylamine (OLA) groups. Produced... 

The research on the automotive brake composite materials is very extensive due to its complex formulation and the used of diverse variety of materials. While various research activities has been applied in this research group, but there are many unknown areas. This subject with the arrival of new materials, especially nanometer materials, has received increasing attention. In this study, the effect of alumina nanoparticles on the performance of automotive brake friction materials were examined. Generally, alumina (as micro particles) used as the abrasive material for many years in the formulation of composite brake pads. But, the effect of alumina on the nanometer scale hasn't been examined... 

The most common type of polymer based composite friction materials are usually in vehicles as the brake pads are used and must characteristics such as high wear resistance, low weight, durability, low noise and stable friction coefficient. Polymer matrix, in addition to providing other material suitable for storage, the final properties, including mechanical properties, heat, friction and wear is also effective. Thermoset resin polymer matrixes (usually phenolic resin) are used in the brake pads which used for automotive and in some cases, rubber particles as powder formulations may be entered, in order to achieve good properties of rubber and resin simultaneously. Nanofillers because of... 

Various composite friction materials containing 40 vol.% organic binder (phenolic resin plus styrene-butadiene-rubber (SBR)) with varying phenolic-resin/SBR ratio were prepared. The content of phenolic resin in each composite was indicated by the resin value (RV) index ranging between 0-100%. The composites with RVs greater than 50% form resin-based friction materials in which the primary binder is the phenolic resin. For RVs less than 50%, the composites become the rubber-based materials where the primary binder is the SBR. The analysis of mechanical properties exhibited that the conformability of the composites increases upon incorporation of SBR. The frictional analysis revealed that type... 

Resin Transfer Molding (RTM) which is one of the categories of Liquid Composite Molding (LCM) process, is considered as one of the most important process in polymer composite manufacturing. To improve this manufacturing method and reaching higher qualities, numerous modified methods has been developed. One of these modified methods is Vaccum Assisted Resin Trasnfer Molding with Flexible Tooling which is considerably applicable in manufacturing parts with high quality, large and complex geometry. Although, this manufacturing method has variety of advantages, there are some problems such as void formation making production difficult and dependent to experimental trial and error. So numerical...