Sharif Digital Repository

The aim of this study is to investigate the effects of nanoclay and rubber particles morphologies on fracture behavior of a lightly cross-linked epoxy. In addition, the role of cavitation resistance of rubber particles on fracture behavior of the nanoclay-rubber-epoxy hybrids was studied. Two types of organoclay and three kinds of rubber modifiers (in micron and nano-size) were incorporated into the epoxy. The results obtained indicate that addition of either intercalated or exfoliated clay increases fracture toughness of the epoxy resin, although the increases in toughness are modest (a 50% increase). The microscopy examinations and the micromechanical models revealed that the... 

Poly (vinylidene Fluoride) (PVDF)/organoclay nanocomposite films were prepared via melt mixing, solution casting and Co-precipitation techniques. The effects of different kinds of nanoclay, sample preparation techniques and electron beam irradiation on PVDF/Nanoclay nanocomposite are reported in this research project. Differential scanning calorimetry was used to study thermal properties and crystallinity of the PVDF and its nanocomposites. The chemical and crystalline structure of the samples was analysed by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) and the mechanical properties of the PVDF nanocomposite were characterized by stress strain test. The degree of... 

The present work investigates a novel approach for improving the oxygen-barrier property of PLA-based film using vinyl acetate-vinyl alcohol copolymer [Poly(VAc-co-VA)] and the nanoclay Nanolin DK4. The permeability, thermal and mechanical properties are studied. To synthesize poly(VAc-co-VA), the hydrolysis of PVAc was done. The nanocomposite blend of PLA/Poly(VAc-co-VA)/Nanolin DK4 was prepared by the solution casting method. The prepared nanocomposite films were optically transparent regardless of poly(Vac-co-VA) and Nanolin DK4 concentrations. The gamma irradiated Poly(VAc-co-VA) was incorporated in the PLA films to probe the effect of cross-linked copolymer on the permeability of the... 

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... 

In this research, porous polyvinyl¬ alcohol (PVA)/Montmorillonite nanoclay and polyvinyl alcohol/polyvinyl pyrrolidone (PVP)/Montmorillonite nanoclay nanocomposite sponges (foams) were fabricated by freeze-drying method. The foams were crosslinked using gamma irradiation. The pore size and interconnectivity of nanocomposites characterized by scanning electron microscopy (SEM), showed bimodal pore size distribution resulting from preparation method.
SEM micrographs displayed that addition of PVP ( wt% of total solid polymer) to the PVA sponges increased the pore size and interconnectivity, due to the optimal number of hydrogen bonds between functional groups of polymeric matrices.... 

Blending different polymers to achieve a compound with modified Physical physical and mechanical properties, has interested researchers for years. Among all, LDPE and HDPE have attracted a great attention for this purpose; specially when a mineral filler like clay is another part of composite. In the related literature, it is proven that small amounts of clay can improve physical and mechanical properties in comparison to virgin blend. Focus of this research is on HDPE/EVA/Clay nanocomposite and its physical and mechanical properties. Having vinyl group, EVA is a compatibilizer that makes clay to disperse better; EVA can also makes the brittle HDPE tougher. At first, HDPE/EVA blend... 

There are so many problems in using of petroleum-based polymers such as their stability in the environment. According to the research carried out on this problem, one of the best ways to overcome this hardship is using of bio-based polymers. The most important bio-based polymer is polylactic acid. The very polymer enjoys the best mechanical properties but it is so expensive that make it impossible to afford. Therefore, in this project, a nano-composite structure of polylactic acid with thermoplastic starch reinforced with nano-particles was produced. After manufacturing, the process of mixture and the best percent for the very mixture for its use in packaging industry were investigated  

Polypropylene block copolymer is used in different industries like pipe productions. This copolymer has proper mechanical properties, specially it has good impact strength, but in some applications it’s elastic modulus (stiffness) is not enough and that leads to some problemes in servise. Nucleating agents influence crystalline structure and properties and also the mechanical properties by controlling the crystallization process. Nanoparticles also have a beneficial effects on physical and mechanical properties. In this study, the effect of adding two types of α-phase nucleating agents (commercial names NA11 and DMDBS) in the form of masterbatch wt 5% with a carrier of polypropylene block... 

The purpose of this project was to produce and examine the Poly(lactic acid)/poly(ethylene-co-vinyl acetate)/ nano-clay nanocomposite by solution casting that can be used for food packaging. In this study, it was observed that solvent evaporation at 4°C gives uniform films, without phase separation and free of voids, in a certain composition of polymers related to the rate of solvent evaporation.According to DMTA results Poly(lactic acid) and poly(ethylene-co-vinyl acetate) with 28% vinyl acetate, were compatible in less than 10% poly(ethylene-co-vinyl acetate) content in blend of them. Also, results of SEM tests showed that ethylene-co-vinyl acetate particle size in blends with 3 and 5... 

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... 

Polypropylene (PP) is a fast growing polymer, particularly in automotive industry, where PP compounds have replaced many different parts made of conventional materials. In the first step, PP-g-MA, as compatibilizer, was synthesized. Two kinds of polypropylenes including a homo- and a block co-polymer were incorporated for this goal. Characterizations via titration and FTIR tests revealed higher degree of grafting reaction when homo-polymer was used for synthesizing PP-g-MA. In the next step, nanocomposites containing 3 wt% nanoclay with three different PP-g-MA/nanoclay ratios of 1:1, 2:1 and 3:1were made using a co-rotating twin screw extruder. Tensile, impact and XRD tests were performed to... 

Polymer/clay nanocomposites (PCNs) are multifunctional materials that have superior mechanical and thermal properties than polymer-based materials. These materials are obtained by adding small amounts of nanoclays to a polymer matrix. In this work, a molecular dynamics simulation was carried out to investigate the thermomechanical properties of thermosetting clay nanocomposites. The polymer matrix was composed of phenolic molecules with the crosslink density of 0.74, and different structures of PCNS were considered by varying the amount of polymer molecules. Molecular dynamics simulations of different nanocomposite structures were used to provide the atomistic insights, the molecular...