Sharif Digital Repository

Polyamide 6 is one of the well-known and oldest engineering thermoplastics, which has many uses in the transportation, automotive, apparel and sports industries due to its high strength, high corrosion resistance and high service temperatures. Cite gears, radiator tank, cylinder head cap and fuel rails can be mentioned as Polyamide 6 applications in the automotive industry. Glass fibers are used as reinforcement in PA6 media in order to enhance mechanical properties like tensile and impact strength. Even though the glass fiber improves the mechanical properties of the components produced from fiber-reinforced composites, it increases the anisotropy properties of the material and making it... 

Today, in many industries polypropylene is used as a polyolefin with favorable properties such as chemical resistance, fatigue strength, electrical insulation, as well as good mechanical properties such as high Yang modulus, good toughness, and so on. On the other hand, polyolefins have poor thermal resistance and high flammability. Over the years, many researchers have been working to reduce their flammability through different methods and increase their thermal resistance. Among these methods, adding materials that delayed flammability or stoped it, can be noted. In the industry, these anti-flammable additives are called flame retardants. Flame retardant additives should be selected to... 

Polymer/layered silicate nanocomposites are good candidates to improve polymer matrices due to enhanced interfaces between nanoclay reinforcement and matrix. So many attempts has been done to improve fabrication methods of these nanocomposites. Polypropylene is a common used engineering material in many industrial applications (general and special). So there is many researches focused on PP/Clay nanocomposites. In this research we tried to investigate the role of clay loading, compatibilizer loading and processing sequence on clay delamination and layer dispersion. We used a blend of two different PPs with different MFI values as matrice. It seems that the blend achieves acceptable... 

Polyamide-6 is a thermoplastic polymer that is classified as electrically non-conductive materials. One way of adding conductivity to the polymer matrices is by utilizing them in a nanocomposite form. Superior mechanical and electrical properties of Carbon Nanotubes make them worthy of being chosen as reinforcement in nanocomposites to extend their operation to a broader range of applications, like conductive nanocomposites, mainly polymer-based matrices. The Nanotubes have chemical affinity and tend to entangle and aggregate. Because of this, to achieve a uniform and remarkable electrical conductivity is hard-to-reach. state of entanglement effects correctly melt methods of polymer blend... 

Blend of Polycarbonate/ poly(butylene terephthalate) is among the most famous blends of polycarbonate/polyester with vast engineering applications and unique properties. Miscibility and compatibilization of this blend are important as they directly influence the general properties.Transesterification which occurs in the melt state, is a series of cutting and rejoining of dissimilar polymer chains. The reaction ruins the order of pure chains and forms block copolymers of different natures. Further progress in transesterification lead into a completely random copolymer of initial chains. Time, temperature and addition of catalyst can effectively influence transesterification.In this study,... 

In this research, we studied the effect of compatibilizer and short glass fiber on microstructure and mechanical properties of PBT/PC blends. Fisrt, Antioxidants and sodium pyrophosphate dibasic were used to suppress transesterification in PBT/PC Blend. The results showed that best composition occur when both of them are used. In the next step, we used 3%wt MBS (methyl methacrylate-butadiene-styrene) and saw that this weight percent of this compatibilizer doesn’t useful. Moreover addition of short glass fiber to PBT/PC was examined and the results showed that mechanical properties of composite are extensively increased. Also in this step, we proved this idea that we can replace some of PBT... 

The consumption of plastics in the world is increasing and this is accompanied by the challenges of production from oil products and carbon footprint, waste production and environmental issues. The solutions to these challenges are material recycling and the production of biocompatible plastics. Polypropylene is a widely used polymer that is commonly used in conjunction with reinforcements such as fiberglass. Natural fibers can be substituted to increase the biocompatibility of the composite, which, despite its many advantages, presents challenges. The most important challenge is the poor adhesion of the fibers and the matrix due to the hydrophilicity of natural fibers and hydrophobicity of... 

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... 

In this study, the synthesis conditions of polyaniline were optimized in order to produce a blend based on polypropylene (PP) containing polyaniline (PANI) with the electrical conductivity in the antistatic range. A form of PANI that has adequate electrical conductivity and thermal stability, which is suitable for melt-mixing and melt-spinning conditions, was synthesized. Thermal stability and electrical conductivity of polyaniline were investigated by thermal gravimetric analysis (TGA), differential calorimetric analysis (DSC) and high-temperature electrical conductivity. It was found that the synthesized PANI has required thermal stability and electrical conductivity (106 ohm.cm) at the... 

Stress whitening is a type of discoloration that can occur in variety of polymers used in automotive and household industries. The current research tries to investigate the effective microstructural parameters such as strain rate, rubber second phase, and branched polypropylene (PP) on the stress whitening in polypropylene in order to propose toughed PP blends with limited stress whitening. It is shown that increasing the strain rate in tensile test results in formation of more visible whitened area within the plastically deformed zone. This is the consequence of further growth of micro-voids at higher strain rates. The results are in accordance with the Mie scattering concepts. Besides, the... 

In this research, a nanocomposite blend of polyamide 6/polystyrene containing polyaniline-coated carbon nanotubes was fabricated via melt blending method, aiming to achieve electrical conductivity in the range of static dissipation. The effect of weight percentage of nanofillers and surface modification of carbon nanotubes with polyaniline on the electrical properties and microstructure of the nanocomposite was investigated. To promote compatibility between the immiscible polyamide 6 and polystyrene polymers, PS-g-MA compatibilizer was utilized, and its effect on the morphology of the nanocomposite blend was examined. Additionally, the influence of weight percentage of nanofillers and the... 

Recycling of polymers, with the aim of environmental protection and economical benefits, is important procedure, which is constantly developing. In this study the effect of the incorporation of recycled PET(r-PET) and recycled polypropylene/Flax(r-PP/Flax) to PP at low (20wt %) and medium content (40wt %) of r-PET was investigated. Polymer compounds were prepared by twin screw extruder followed by injection moulding. The effect of r-PP/Flax and r-PET on PP was evaluated using different techniques such as scanning electron microscopy (SEM), differential scanning calorimetery (DSC), rheological behavior, and mechanical properties (tensile modulus, yield strength, and charpy notched impact... 

Taghizadeh Manzari, M. (MehrdadThe main goals of this project are studding the effect of carbon nanotube on the properties of PA6/PA66 matrix and miscibility of PA6/PA66 blend. So PA6/PA66/CNT nanocomposites were compounded by melt mixing method and samples were prepared by injection molding. Due to study miscibility of PA6 and PA66, we used DMTA test and found that PA6 and PA66 are miscible because of existing one pick on DMTA graph. Also DSC test results confirmed that PA6 and PA66 are miscible. Moreover, according to DMTA results, modulus will be rose by increasing CNT content. Mechanical test showed same results in this case. Adding 1%CNT to matrix caused 10% improvement in modulus and... 

Preparation of binary polyamide 6 (PA6) / carbon nano tube (CNT) and ternary PA6 / EPR-g-MA / CNT has been carried out using melt mixing. Four PA6s were selected with different viscosities (and molecular weights) and molecular structures (linear or branched). Effect of CNT content (up to 2 wt%) and mechanical mixing conditions (rotor speed, temperature and time of mixing) have been investigated. Ethylene- propylene rubber grafted maleic anhydride (EPR-g-MA) was selected at 20 wt% as toughening agent for ternary nanocomposites and mixing sequence of PA6 , EPR-g-MA and CNT has been investigated. Morphological observations showed that dispersion of CNT is done by erosion mechanism at low melt... 

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 today’s world the growth in population make food production and also the packaging industry increase. Finding new ways to enhance the efficiency of packaging is become so important beyond researchers. As the randomized co-polypropylene is the most suitable materials for this industry many attempts have been made to control its melting behavior with the aim of expanding their application in the packaging industry. The study in this field indicate the dependence of the melting behavior on the structural characteristics of the material such as molecular mass, chain structure, type of crystalline structure, and the amount of dispersion of the crystals thickness. Due to the lack of proper... 

Although studies have shown interesting piezoelectric and dielectric properties of PZT containing composite piezoelectric ceramics, there has been no systematic investigation on the PZT-PCN, especially on the porous one.In this study, the dense ceramics of 0.8Pb (Zr1/2Ti1/2)O3–0.2Pb(Co1/3Nb2/3)O3 abbreviated to (PZTCN) systems were successfully prepared by the columbitewolframite precursor method via the mixed oxide technique. Porous PZT-PCN ceramics were prepared by burnable plastic sphere process (BURPS) technique with three types of pore forming agents (PFAs), poly vinyl chloride (PVC), stearic acid (SA), and poly methyl methacrylate (PMMA) at different weight percentages(5, 10,and 15... 

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...