Iranian Journal of Polymer Science and Technology
Year:2016 | Volume:29 | Issue:4|Papers Count:7

The effect of modified starch on the properties of poly (styrene-ethylene- propylene-styrene) tri-block copolymer was studied. Chemical treatment of starch with maleic anhydride was accomplished in an internal mixer in the presence of glycerol. The reaction was confirmed using Fourier infrared spectroscopy (FTIR) and titration. The blend samples containing 10, 20, 30 and 50 wt% were obtained by melt blending and their mechanical, morphological and dynamic-mechanical properties were studied. Scanning electron microscopy (SEM) images displayed droplet-matrix morphology and with increases in modified starch up to 50 wt% some partial co-continuous morphology was also observed. With increase of modified starch in the compound, the size of dispersed phase increased. DMTA results revealed that the partial compatibility was obtained because of slight difference between glass transition temperatures of two phases in the presence of modified starch. The peak of modified starch shifted to higher values and the differences between the two peaks decreased, indicating partial compatibility. Mechanical properties including tensile, elongation-at-break and modulus were also determined and the results showed that the mechanical properties of the sample were higher than those of neat TPS because of the higher compatibility. Tensile strength was decreased with increase in modified starch content due to the absence of strong interfacial adhesion. Moduli of the samples were increased with increase in modified starch content due to higher stiffness of starch. Biodegradability of the samples was evaluated by weight loss percentage using compost test. A rapid degradation was observed in the first 45 days and with increase of the modified starch content the degree of degradation was increased.

Chitosan (Chito) as a biopolymer with high antibacterial, biocompatibility and biodegradability and polyaniline (PANI) as a conductive polymer and silver (Ag) nanoparticles to enhance antibacterial property were used to preparepolyanilin-chitosan-silver (PANI-Chito-Ag) nanocomposites. The synthesis of PANIChito composite and PANI-Chito-Ag nanocomposite was performed through anilinepolymerization in the presence of Chito and Ag. In order to evaluate the physicochemicaland antibacterial properties of synthesized composite and nanocomposites, severalcombinations of components with different weight ratios were used. Antibacterialtests were performed using two different types of bacteria: Escherichia coli (gramnegative bacteria) and Staphylococcus aureus (gram-positive bacteria) to determinethe antibacterial capability of the PANI-Chito-Ag nanocomposite. The obtained results showed that higher Chito and silver contents produced stronger antibacterial property.The biodegradability test results confirmed that, the biodegradability increased as the content of Chito increased. Also, by increasing Streptomyces (gram-positivebacteria) concentration in natural soil, the biodegradability rate of nanocompositewas enhanced. The results obtained from thermogravimetric analysis (TGA) testsalso indicated improvement in thermal stability of PANI-Chito-Ag nanocompositecompared to that of pure Chito. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy(EDX) were used to analyze and characterize the composition and structure of PANIChito-Ag triple hybrid nanocomposite. The results confirmed uniform distribution of Ag nanoparticles within the polymer matrix.

In recent years many research works have been carried out on anti-corrosive nanocomposites coatings containing mineral reinforcements. The most important criteria in these attempts are polymerization method and the type of matrixand reinforcement of nanocomposites. In this regard, the physical and mechanicalproperties of the polymers in which a small amount of filler is used can be improved. Inthis research, an epoxy-clay nanocomposite was synthesized by in-situ polymerizationmethod using a resin matrix based on bisphenol-A type epoxy and montmorilloniteclay (Closite (R) 15A). The treatment was used at different ultrasonic stirring times todisperse 1-4 weight percentages of clay particles into the matrix. The structure of synthesized epoxy-clay nanocomposite was studied by scanning electron microscopyand X-ray diffraction techniques. The average size of clay particles was determined by X-ray diffraction measurement. Then, anti-corrosion properties of epoxy-claycoatings, prepared under different ultrasonic durations and applied on carbon steelpanels, were investigated by Tafel and electrochemical impedance spectroscopytechniques. For this purpose, the carbon steel panels coated with these coatings were immersed in 3.5% sodium chloride solution and tested at different immersion times.The results indicated that a nanocomposite containing 1% clay, synthesized, stirred60 min ultrasonically, produced smaller particle size, lower corrosion current densityand higher coating corrosion resistance than the other composite formulations. This nanocomposite provided superior protection against corrosion in sodium chloridesolution.

Because most contaminants in water create strong interactions with hydrophobic surfaces, there are usually problems such as flux decline and pore blocking in polyethylene (PE) membranes due to irreversible adsorption of foulantson their intrinsic hydrophobic surface. Therefore, in this work, attempts were made to improve the properties of PE membranes in terms of water flux and membranefouling resistance by dispersion of silica nanoparticles (NPs). First, NPs were synthesized by sol-gel method at two concentrations of ammonia (0.5 and 1 mol/L).The synthesized NPs with smaller size were used to fabricate the mixed matrix PEmembranes containing 0, 0.5, 1 and 2 wt% NPs. FE-SEM and EDX analyses wereemployed to evaluate the morphology and structure of the fabricated membranes andconfirmed the presence of NPs in the membranes matrix. The results of pure water flux test revealed that the membrane containing 1 wt% NPs displayed the maximumflux of 30 L/m 2.h. Furthermore, the performance and fouling behaviors of membranesduring filtration of humic acid solution, one of the most important contaminants of water resources, were studied using a classical fouling model. Fouling mechanism analysis showed that for neat and NPs-embedded membranes containing 0.5 and 2wt% NPs, the best fit of the data was obtained by cake layer formation as well as the intermediate blocking mechanisms. However, the best fit of the experimental data of NPs-embedded membrane containing 1 wt% occurred with only cake layerformation mechanism. The investigation on membrane fouling resistance showed that1 wt% NPs-embedded membrane displayed 58% maximum flux recovery and 52%reversibility to total fouling ratio, respectively

N anomagnetic hydrogels, based on κ-carrageenan and acrylic acid, were prepared for removal of methyl violet from aqueous solutions. k-Carrageenan/ acrylic acid-based hydrogels were prepared in aqueous solution in thepresence of methylene bisacrylamide (MBA) and ammonium persulfate (APS), the former as a crosslinking agent and the latter as an initiator. The nanomagnetichydrogels were obtained by co-precipitation of Fe (II) and Fe (III) ions in presence ofammonia solution. The effects of different variables such as contact time, temperature, amount of adsorbent, and pH were examined in relation to the sorption behavior of themethyl violet. The structure of the nanomagnetic hydrogels were studied by infraredspectroscopy (IR), thermogravimetric analysis (TGA), scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The results of scanningelectron microscopy and transmission electron microscopy showed that the magneticnanoparticles in the hydrogel matrix were dispersed satisfactorily with approximatesize of 5-15 nm. The maximum amount of adsorption reached approximately 86%under optimum conditions of 60 min, pH 8 and initial dye concentration of 10 ppm.The adsorption capacity increased with temperature and pH. This study showed thatthe obtained nanomagnetic hydrogels with high removal efficiency and low reactiontime could be used as effective adsorbents of methyl violet dyes from aqueoussolution and for simple separation by a magnetic field. The equilibrium process ofremoving metal ions by nanomagnetic hydrogels could be evaluated efficiently usingthe Langmuir, Freundlich and Temkin models.

Glass fiber/phenolic composites are effectively used as heat shields for fabrication of cooled combustion chambers. To improve the performance of these composites as well as to lower their costs, the use of nanosized silicondioxide (SiO 2) particles has been adopted. In this work, we investigated the effect ofnanosilica on properties, heat stability and ablation properties of glass fiber/phenoliccomposites. Glass fiber/phenolic/nanosilica composites were made of 1, 2 and 3wt% of well-dispersed silica nanoparticals in a phenolic resin. The average size of silica nanoparticals was 45 nm. These nanocomposites were prepared by hot-pressprocess. Ablation properties of the composites were studied by oxy-acetylene torchenvironment and their mass and linear erosion rates were evaluated. The thermalstability of the produced composite structures was examined by means of thermalgravimetric analysis in air with dynamic scans at a heating rate of 10oC/min fromroom temperature to 800oC. Bulk samples, of about 20 ±1 mg each, were tested. Theresults indicated that nano-SiO2 increased the thermal stability of nanocompositesso that their linear and mass erosion rates after modifying with 3 wt% nanosilicadropped by 58% and 53%, respectively. The 3-point bending test results showedthat bending strength and modulus of the as-received composites increased withpercentage nanosilica added up to 2 wt%, beyond which they decreased. For the glassfiber/phenolic composites with 2 wt% nanosilica particles, embedded in the matrix, strength and modulus increased about 40% and 19%, respectively, in comparison tothose for neat glass/phenolic composite.

The novel conductive nanocomposite and composite from polyaniline (PANI) were prepared. The composites were synthesized by in situ oxidative chemical polymerization of aniline on silica- and nanosilica-supported sulfuric acid. There action was carried out in a mortar and ammonium persulfate was used as oxidantunder solvent-free condition at room temperature. Structure, size and morphology of the synthesized nanocomposite and composite were determined by Fourier transforminfrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomicforce microscopy (AFM). Conductivity was measured by four-probe technique and revealed that the samples not only had the conductivity in the range of conductive polymers (~0.4 S/cm) but also they showed high conductivity as composites and blends of polyaniline reported by others. Synthesis of composites (nanocomposites) and formation of polarons were confirmed by FTIR and UV-Vis. SEM images showed that silica particles were thoroughly coated by PANI and all were amorphous.According to the TEM and AFM images, particle size in composite and nanocomposite was in the range of 1-5 mm and 35-49 nm, respectively. Furthermore, the surface morphology, shape and dimensions of particles obtained by AFM strongly supportedthe SEM and TEM observations related to polymer deposition on the silica particles.The key benefits of the approach used in this research are the preparation of novelconductive composite and nanocomposites with the polaron structure under greenchemistry condition of dopant solid acids including silica- and nanosilica-supportedsulfuric acid.