Iranian polymer journal
Volume:21 Issue: 9, 2012

Mg–Al–Fe ternary layered double hydroxides (LDHs) were synthesized based on Bayer red mud by a calcination–rehydration method, and characterized using powder X-ray diffraction and thermogravimetric analysis techniques. The synergistic flame-retardant effects of red phosphorus (RP) in ethylene vinyl acetate (EVA)/LDHs composites were studied with the limiting oxygen index (LOI), the UL 94 test, the cone calorimeter test (CCT), and the smoke density test (SDT). And, the thermal degradation behavior of the composites was examined by thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR) analysis. Results showed that the LOI values of the composites with RP were basically higher than those of the pure EVA sample and composites containing LDHs only. And the addition of a suitable amount of RP in EVA/LDHs/RP composites can apparently favor UL 94 test. In the UL 94 test there was a V-1 rating and dripping phenomena for the composites containing 50 % LDHs. However, the composites containing 47.5 % LDHs and 2.5 % red phosphorus did not drip. The CCT results indicated that the heat release rate (HRR) of the EVA/LDHs/RP composites with a suitable amount of RP decreased in comparison with that of the EVA/LDHs composites. The SDT showed that RP was helpful to smoke suppression. TG-FTIR data showed that the EVA/LDHs/RP composites show a higher thermal stability than the EVA/LDHs composites. A suitable amount of RP in EVA/LDHs/RP composites resulted in an increase in LOI values, a decrease in the HRR, the achievement of the UL 94 V-1 rating with no dripping phenomenon, a good smoke suppression character, and a high thermal stability.

Microwave-promoted phthalic acid–formaldehyde–resorcinol (M-PFR) based chelating resin was synthesized in DMF media at 2.45 GHz and its performance was compared with conventional phthalic acid–formaldehyde–resorcinol (C-PFR) chelating resin, synthesized earlier in our laboratory. M-PFR resin was characterized by FTIR and elemental analysis. Thermal stability and structural morphology of the synthesized resin were evaluated by TGA, SEM, and BET analysis. The energy of activation (E a) was estimated by thermal analysis data using Broido and Horowitz–Metzger methods. The physico-chemical properties of M-PFR resin have also been determined. The adsorption capacities of M-PFR resin for Cr(III) and Pb(II) have been studied by batch equilibrium method, and were found maximum 0.43 and 3.12 mmol/g at pH 6.0, respectively. Operational variables such as pH, metal concentration and equilibrium rate were optimized. The sorption equilibrium data follow Langmuir and Freundlich adsorption models. A pseudo-second order kinetic model has been proposed to correlate the data. Sequestration of Cr(III) and Pb(II) from estuarine sediment extract was carried out at optimized K d values in tartaric acid media by column method. The regeneration of M-PFR resin was successfully carried out by 2 M HCl and reused several times

The present work involved a thorough study on silane-modified silica filler with special focus on its chemical interaction with polydimethylsiloxanes (PDMS) and the structural model of the modified filler. The samples prepared by addition of modified silica were characterized by Fourier transform infrared spectroscopy (FTIR), specific surface test, scanning electron microscopy (SEM) and fluorescent microscope. FTIR results confirmed the successful silica surface modification with silane coupling agent. The sample containing 80 phr (parts per hundreds of rubber) modified filler with weak ratio of Si–OH/Si–C group absorbance areas (A 1/A 0) showed weak formation of filler agglomerates while a stronger interfacial interaction could take place between the modified silica and PDMS. Specific surface results showed that the dispersion of silica can be improved when the amount of silane modifier to silica reached 2.0 wt%. SEM and fluorescent microscope showed that the filler aggregation was observed in cases of higher silica loading. As expected, when the silica with surface treatment was compared with those without surface modification, the filler particles were found to be fairly well dispersed in PDMS matrix.

Aromatic azides are important intermediates with a variety of applications in organic and bioorganic chemistry. In this article an efficient, simple and effective method for one-pot synthesis of aryl azides from aromatic amines is described. In this procedure diazotization of aromatic amine occurs under mild conditions using cross-linked poly(4-vinylpyridine)-supported nitrite ion, [P4-VP]NO2, in the presence of concentrated H2SO4 at low temperature (0–5 °C). The in situ generated aryl diazonium salts, followed by azidation with sodium azide in water at room temperature to produce the corresponding aryl azides by the salient of nitrogen gas (Sandmeyer-type reaction). After optimization of the reaction conditions, a good range of available aromatic amines were also subjected to diazotization–azidation by using [P4-VP]NO2/H2SO4/NaN3 in water. Various aromatic amines, with electron-withdrawing groups as well as electron-donating groups, were transformed into aryl azides in good yields. The aryl azide products were characterized by Fourier transform infrared, some of them were also characterized by proton nuclear magnetic resonance (1H NMR) spectroscopy, and physical properties were compared with the literature values of known compounds. The present method is compared with other reported methods in the literature, for preparation of aryl azides. The advantages of the present method over conventional classical methods are; mild reaction conditions, safe handling, rapid, and very simple work-up. The spent polymeric reagents can be regenerated and reused for several times without significant loss of their activity. In this paper we report the first procedure for facile and rapid diazotization–azidation using cross-linked poly(4-vinylpyridine)-supported nitrite ion.

Cu+2 ion doped polyanilines (PANI) were synthesized by oxidative polymerization of aniline using ammonium persulphate in presence of copper sulphate solution having varying Cu+2 ion concentration. Products were characterized by UV–Vis and FTIR spectroscopy. Morphology of the products was observed by SEM. Morphology of the emeraldine-base form of PANI (EB-PANI) changed when doped with Cu+2 ion and its concentration had also shown influence on the morphology. Thermal stability of the Cu+2 doped PANI was found to be less than that of EB-PANI. Experimental results showed that Cu+2 ions were successfully incorporated into the polymer and there was a strong interaction between the Cu+2 ions and PANI chains. Formation of semiquinone segments (polaron species) upon coordination with Cu+2 ions was undoubtedly demonstrated by UV–Vis and FTIR spectroscopic results. FTIR spectroscopy showed shifts towards the lower wavenumbers for the Cu+2 ion doped PANI as compared to EB-PANI. An increase in intensity of the band at 1,130 cm−1 was observed which corresponds to the electronic like absorption confirming the doping of EB-PANI. Crystallinity was studied by powder XRD analysis and it was found that Cu+2 ion doped PANI has developed a crystalline structure while EB-PANI is amorphous. Conductivity was found to be dependent on the concentration of the Cu+2 ions and there was an optimum concentration of Cu+2 ions for getting the highest conductivity.

Novel hydrogel nanocomposites were synthesized by solution polymerization of acrylamide in the presence of carrageenan biopolymer and laponite RD clay. Laponite was used as an inorganic cross-linker. Ammonium persulfate was applied as an initiator. The structure and morphology of the nanocomposites were investigated using XRD, scanning electron microscopy, and transition electron microscopy techniques. The influence of both laponite nanoclay and the carrageenan content on the swelling degree of nanocomposites was studied and it was found that all nanocomposites containing carrageenan component have a high swelling degree compared to a nanocomposite without carrageenan. The obtained nanocomposites were examined to remove a cationic crystal violet (CV) dye from water. The effect of carrageenan and clay contents on the speed of dye adsorption revealed that while the rate of dye adsorption is enhanced by increasing the clay content, it was depressed as the carrageenan content increased in nanocomposite composition. The results showed that the pseudo-second-order adsorption kinetic was predominant in adsorption of CV onto nanocomposites. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The results indicated that the experimental data fit the Langmuir isotherm best. Maximum adsorption capacity was obtained for carrageenan-free nanocomposite with 79.8 mg g−1 of adsorbed CV onto nanocomposite.

The paper presents an assessment on the properties of three different types of masonry mortars, namely Portland cement mortar (CM), polymer cement mortar (PCM) and polymer mortar (PM) of various compositions. The effect of binder content (cement and/or epoxy) on CM, PCM or PM has been explored in the study. An assessment was carried out on the basis of mechanical (compressive, tensile and flexural strength), physical (water uptake, chloride ion permeability), morphological (porosity) and thermal (coefficient of thermal expansion) properties of the mortars. A comparative cost analysis of the mortars is also discussed in this article. The results show that the mechanical strength of both PCM and PM improves markedly with the addition of epoxy resin, and the higher rate of incremental strength is found for PM. Consequently, the chloride ion penetration, water uptake, porosity and thermal expansion of the mortars decrease significantly with the resin content, but the rate of drop in chloride ion penetration, water uptake, porosity and thermal expansion is much higher for PM. The test results indicate that the variation of binder content (epoxy/cement) is found to be the key factor determining the mortar properties and cost.

The zinc ion self-crosslinkable polyacrylate latexes (PAs) cured at room temperature were synthesized by seeded semi-continuous emulsion polymerization with zinc oxide (ZnO) as crosslinker. The ZnO and methacrylic acid (MAA) mass contents, method of ZnO introduction in relation to the degree of crosslinking, and the properties of self-crosslinkable latices are examined and discussed. The characterization techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA) have been used to determine the structure and properties of PAs. The experimental results show that in a certain range, the average particle size decreases with an increase in the content of MAA, while the latex stability is undoubtedly improved. The optimum mass content of MAA is 12 % of the total monomers. The optimum amount of ZnO needed is 25 % (mole fraction) of MAA, and the optimum temperature of ZnO introduction is 60 °C. TEM analyses show that the latex particles are coarse spherical particles with surface enriched with comprising abundant carboxyl groups, and zinc ions are dissociated as zinc ammine complex in the aqueous phase. FTIR analyses confirm that the chelate crosslinking occurs between zinc ions and carboxylic acid during the film-forming process. The DSC results indicate that the glass transition temperature (T g) of PAs increases as a function of the formation of a coordinate structure, and the obtained film exhibits excellent initial hardness and sandability. TGA analyses demonstrate that the introduction of ZnO evidently enhances the thermal stability of self-crosslinkable PAs.

A quaternized highly branched polyacrylamide was synthesized and used as an efficient multi-site polymeric phase transfer catalyst in dichlorocyclopropanation reaction. The quaternized highly branched polyacrylamide was synthesized via two steps. First, a highly branched polyacrylamide was synthesized via self-condensing vinyl polymerization using appropriate molar ratio of monomer to diperiodatocuprate(III) solution. In the second step, 3-acrylamidopropyltrimethylammonium iodide was polymerized on peripheral area of the highly branched polyacrylamide in the presence of diperiodatocuprate(III) solution. The thermal behavior of highly branched polyacrylamide and that of the quaternized highly branched polyacrylamide was studied by DSC and TGA analyses. Then the activity of the synthesized quaternized highly branched polyacrylamide was investigated as phase transfer catalyst in dichlorocyclopropanation of olefins in biphasic medium. To this purpose, the synthesized catalyst was used in generating dichlorocarbene from chloroform in aqueous sodium hydroxide solution which was subsequently added to olefins. This catalyst is very active and its application yields high volume of products which are obtained in relatively short time. Various factors which influence the rate of dichlorocyclopropanation reaction, such as base concentration, stirring speed, temperature and amount of catalyst, are studied and a mechanism for addition reaction of dichlorocarbene to olefins is proposed. This efficient phase transfer catalyst was reused several times without any loss of activity.

In this study, viscoelastic properties of polymeric composites were investigated through a non-destructive test (NDT) method based on longitudinal free vibration. First, three different polyester composites reinforced separately with carbon, glass, and hemp fibers, as well as, one polyester composite sample reinforced with poplar wood powder were manufactured via pultrusion and hand lay-up methods, respectively. In the proposed resonant free vibration non-destructive method, each rod-shaped test specimen was hit by a hammer at one end of specimen and immediately the acoustic response of the specimen was recorded by a microphone at the other end of the sample. Subsequently, the recorded sounds were analysed using fast Fourier transform technique. Then, frequency of the first mode of vibration for each composite specimen was utilised to calculate modulus of elasticity. Further, decrement in vibration energy as a function of time was examined to obtain loss parameter (tan δ) of the provided composites. Moreover, parameters (i.e., elastic modulus and tan δ) were also compared with those determined by dynamic mechanical thermal analysis (DMTA). It is found that the results obtained from the examined non-destructive test method are in consistent with those measured by DMTA approach, providing reliable, accurate and quick responses.