Sharif Digital Repository

Friction composites, as a part of vehicle safety system, should hold some characteristics such as high wear resistance, low weight, durability, low noise, stable friction coefficient, availability and low price. It is very interested to use mixture of rubber and resin in friction materials to reach good properties of both rubber and resin simultaneously. This mixture is especially used in railway’s brake pads. Fibrous reinforcement is another important ingredient in friction composites. Asbestos used to be the most significant fibrous reinforcement due to its appropriate tribological specifications but the recent ban on asbestos by environmental protection agency has forced the friction... 

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... 

In recent years, using the nanoparticles has caused a great revolution and development into the materials structure and the polymer science developed corresponding to important role of it in consumer goods. So Carbon Nano Tubes (CNTs) belonging to the precious physical, Mechanical and thermal properties has been studied. The CNT is mixed by mechanical and solution methods with elastomeric matrix. In this research the mechanical method used, because of industrial applications. Although, there are many challenges against dispersion owing to weak cohesion between CNTs and matrix in the mechanical method. The progress in rubber composites reinforced by CNTs and other reinforcement and as well as... 

In this research the effects of addition of clay in phenolic glass fiber reinforced composite has been investigated. Layered clay/phenolic nanocomposite resin systems were first prepared with 0.5, 1.5 and 2.5 wt% of Cloisite Na+ (CN) and Cloisite 30B (CB). After that the suspension was hold in an ultrasonic bath for 30 min in order to enhance nanodispersion of the clay platelet within the resin. The phenolic/clay solution was used to impregnate the glass fabric using the solvent impregnation method. After suspension for 2 days in the room with natural condition, the impregnated fabrics were pre-cured at 135 ˚C in an oven for 3.5 min to obtain B-stage prepregs. Seven layers of prepregs (150... 

Automotive brake pad is one of the most widely used composites. Commonly, more than 10 components are applied to make these materials and due to the large number of components and interactions between them, choice, explaination of the behavior and optimization of brake friction materials are some industry's challenges. Until now, some methods have been presented to design and optimization of these materials, but due to different complexities, there is lack of practical method that could be used for explaining the tribological behavior, engineering calculation and optimization of brake friction materials. Today, formulation of the current brake pads in the industry has mainly come from trial... 

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... 

Vulcanization is one the most crucial process in elastomer manufacturing products. It has been shown that network structure and curing kinetic are strongly dependent on curing system formulation. In addition reinforcing fillers in elastomers can affect them as well. By commencement of nanofillers in rubber domain, effects of nanofiller presence on rubber behavior have been investigated by reaserchers.
In this Project the effect of different curing system formulations on vulcanization kinetic and network structure of NR/SBR elastomeric matrice filled by nanodiamond is investigated. Different ingredients and nanodiamond were added to matrix by mechanical mixing in two roll mill. The... 

Polyamide or Nylon, due to its remarkable mechanical and tribological properties, has many engineering applications. Hence, improving the properties can develop the polyamide applications. In this study, Polyamide 6 (PA6) has been used as matrix with nanodiamond (ND) reinforcement. Spherical shape, chemically active surface as well as remarkable mechanical properties make nanodiamond an ideal candidate for improving polymers properties. Poor dispersion and agglomeration are present however major problems in achieving improved properties in nanocomposites. To deal with this problem, nanodiamonds were surface modified using Ethylenediamine (EDA) and Hexamethylenediamine (HMD). Nanocomposite... 

Polyamide6 has many engineering applications due to its physical, mechanical and processability properties. However, its low impact resistance limits the use of polyamide6. One of the common ways to overcome this problem and extend the range of polyamide6 application is its elasticity with elastomeric materials, which reduces the strength and modulus (tensile and flexure) in comparision with neat polyamide6. To overcome this limitation, various reinforcements, often fiber or particle-shaped, are used. Today, with the development of nanoparticles, this effort is being made to use nanoparticles, especially carbon nanoparticles with unique properties. Recent research has shown that the addition... 

Flexible polymers (elastomers) are especially suitable for dynamic applications, and carbon fillers are well-known filler for elastomers. These are widely used in elastomer matrices for various commercial applications. Some of carbon nano fillers like Nano Diamond cannot impart such high degree of reinforcement to polymer matrices mainly because of improper filler dispersion and lack of strong filler-polymer interaction. In this effort, we examine the effects of two different nanostructured carbons when they are incorporated in a rubber matric in terms of mechanical, thermal and electrical properties of the nanocomposites. Different ingredients and hybrid nanofillers were added to matric by... 

Supercapacitors are one of the most important energy storage devices that have been researched with respect to the development of hybrid cars. Polymer composites have received much attention due to the electrochemical properties of conductive polymers and the synergistic effects of the composite components. In the present Thesis, in order to investigate the synergistic effect of gold nanoparticles with MnO2 nanorods as a metal oxide and polyaniline as a conductive polymer and graphene as a carbon material, two groups of composites were synthesized in the presence and absence of graphene. Characterization of the electrode material is carried out by XRD, FT-IR and FE-SEM tests. The... 

Hydrogels are of growing interest for fabrication of wearable strain sensors due to their intrinsic ionic conductivity, flexibility, and biocompatibility. Herein, to improve the mechanical properties of hydrogels, conventional covalent crosslinking is replaced with novel physical cross-linking. First, the microstructure and properties of pure hydrogel is optimized. Then, Cellulose nanocrystal (CNC) is added to the optimized gel to reinforce it. Finally, through a sequential strategy, aniline monomers are diffused into the gel network and are in-situ polymerized accordingly, providing high conductivity of 21.7 S/m. The resulting hydrogel has the stretchability of 2500% and the toughness of... 

polyamides have found great attractions in wide variety of applications due to their desirable mechanical and tribological properties and appropriate processability. Pure polymers are not suitable for this kind of application due to their low mechanical strength. High strength materials are needed for abrasive applications. Polytetrafluoroethylene (PTFE) is one of the most popular materials for abrasive applications. In this study the effect of PTFE and surface modification on PA/PTFE composite properties is investigated. duo to modification of PTFE powder, PTFE is exposed to sodium naphtalenide (Na/naphtha) etchant so as to deflurinate the surface for obtaining carbonyl, carboxyl and... 

Polydimethylsiloxane (PDMS) is one of the most important organosilicon elastomers. This polymer has a wide application such as medical engineering due to the unique characteristics, variety and ease of manufacture. Nowadays, the use of nanoparticles such as carbon nanotubes for improving the properties of elastomers is highly regarded owing to the fact that the improvement of properties such as mechanical properties broadens the applications of PDMS. Diamond nanoparticles has been the focus of numerous researchers in the past decade. In fact, nanodiamond has a good mechanical abrasion and thermal properties. In addition, the investigations proved that the nanoparticle is valuable in terms of... 

Cellulose nanocrystals as a reinforcement in polymer nanocomposites are part of current research for reasons such as source renewable, biocompatibility, nanoscale dimensions, high specific surface area, and surface chemistry. This research used cellulose nanocrystals as a corrosion inhibitor carrier in epoxy-based composite with 1% by weight. In order to load the corrosion inhibitor, firstly, cellulose nanocrystals were surface modified by aniline so that they can spread well in the hydrophobic epoxy matrix. Different corrosion inhibitors were tested for adsorption on the surface of cellulose nanocrystals modified with polyaniline, but finally the acidic agent of phosphoric acid showed... 

Nowadays, replacement of traditional cast iron shoes with composite brake blocks is a main project in railway systems. The main purpose of this replacement is noise reduction( for example by about 10dB for a 100km/h freight train). One of the main sources of noise emission is the rolling sound of the wheel on the rail. The rougher and more out-of-round wheel surface, the greater the noise produced. Cast iron brake shoes, still widely used on freight wagons, make the wheel surface much rougher than composite brake blocks due to the fusing of minute metal particles into the tread surface during braking. It is therefore necessary to replace the current cast iron brake shoe with a synthetic... 

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... 

Chitosan is a biocompatible and biopolymer with unique characteristics. Nanodiamonds that are basically carbon based nanoparticle have excellent mechanical, thermal stability biocompatibility bahviors. Combination of these two materials helps to the advantage of all the desirable features of both material and compensate low mechanical properties and strength of chitosan. In this study, we examine the composition of different percentages of nanodiamonds in chitosan and effect of modification on properties of the nanocomposites. The thermal behaviour, swelling behaviour and water contact angle of different nanocomposites were analyzed. Finally, to determine the distribution of the... 

In recent decades, nano-structured materials have been allocated specific position for wide use in various fields. The nano-diamonds has attracted the attention of many researchers. The inherent characteristics of a diamond like spherical structure of nanoparticles and carbon atoms which have used their full capacity in the chemical bonds,also the same surface as the radiography particles which have empty orbital, provides an ability to perform a variety of surface modification on the particle . This article introduces the nanocomposites based on polymer, constituents specification and discuss properties of nanocomposites after mixing components together. Lots of studies was on... 

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...