Iranian polymer journal
Volume:12 Issue: 4, 2003

The thermal behaviour of an epoxy/polyester powder coating was studied by using differential scanning calorimetry (DSC). Fourier transform infra-red spectroscopy (FTIR) method was employed to evaluate the processes occurring prior to and after curing process. Electrochemical impedance spectroscopy (EIS) was employed to assess performance of differently pretreated powder coated aluminium alloy substrates. The DSC method allows the description of powder coating systems. The spectra showed that the curing process starts at approximately 150ºC and terminates at about 250ºC. According to the impedance data, relatively good performance of the powder coating is due to a high ohmic resistance of the coating prior to and after saturation with water. The data also revealed a better performance of the degreased samples compared to samples treated with polyacrylic acid (PAA). Samples treated with PAA + H2ZrF6 (PZr) have shown corrosion inhibition over 60 days of immersion time. Corrosion protection was observed for chromate/phosphate conversion coated (CPCC) samples even after completion of the test.

Treatment of cotton fibres has been studied in air and oxygen plasma and the treatment time, nature and flow rate of the gas, and plasma power have been varied. In order to establish the chemical effect of plasma treatment on cotton fibres the following tests have been performed: Cuprammonium fluidity test, weight loss measurement, determination of carboxyl groups, carbonyl group identification, FTIR analysis and measurement of the ASTM yellowness of the untreated and plasma treated cotton fabrics. In addition, vertical wicking studies and the effect of ageing of the plasma treatedsamples on the rate and the amount of dye uptake have been investigated. The plasma treatments lead to surface erosion of the cotton fibres which generates a weight loss, accompanied by an increase in the fibre carboxyl group and carbonyl group contents. The increase in fibre carboxyl group content leads to a more wettable fibre and the rate of fabric vertical wicking is increased. The direct dye (chloramine Fast Red K) uptake of treated samples increases almost linearly with the increase in fibre carboxyl group content caused by plasma treatment, but progressively decreases with increase in the ageing time after oxygen plasma treatment. Ageing after plasma treatment also increases the fabric yellowness.

The analysis of literature data has given strong evidence that the use of Ni and Cooraganic dithioderivatives, as components of bifunctional catalysts, not only catalyzes the polymerization process, but it protects the system from oxidative ageing as well. As part of the continuing work of the first part for the present research work, studies have been carried out on the stabilizing properties of cobalt-containing catalytic dithiosystems (Co-dithiophosphates + DEAC) in the processes of 1,4-cis polybutadiene (PBD) thermal and photodegradation. To reach the most effective combination of the catalytic and stabilizing properties of catalysts, it is necessary to introduce into the complex the ligands of functional groups and the dithio groups as well to provide synergistic effect of thermo and photooxidative stability. The above system’s effectiveness has been confirmed to surpass the activity of the pure cobalt dithiophosphates and the antioxidant Agidol (NG-2246) used in industry.

Ethylenediaminetetraacetic acid (EDTA) as a suitable and common complexing compound was inserted into the polymer backbone with polyaddition reactions separately between hexamethylenediamine (HMDA) or poly(ethylene glycol) (Mw=1000, PEG1000) and ethylenediaminetetraacetic acid dianhydride (A-EDTA). The prepared polymers were soluble in water and carboxy functional groups have been connected to the polymer chains. The polymers were characterized by UV-vis, FTIR and 1H NMR spectroscopy, elemental analysis and thermal gravimetry methods. The carboxy functionalities were measured by titration. The metal complex polymers were separated by dialysis tube and also characterized by spectral techniques and thermal gravimetry.

In the present work, the two-step so-called “in-in” method, is used to produce model networks with well-defined and controllable structure. For this purpose, two different networks are produced: (a) polystyrene network, including polystyrene star-shaped polymers connected by linear polystyrene chains. (b) polystyrene-polyisoprene network, including polystyrene star-shaped polymers connected by linear polyisoprene chains. The structural parameters of the synthesized networks are determined by SEC, light scattering and theoretical calculations later. In such anionically synthesized networks, each junction point, carries many pendent chains on itself (the arms of the initial star polymer), which have rotational degrees of freedom under the conditions of use.

The melt rheology of ethylene propylene diene rubber (EPDM) before and after modification with 5 and 10 phr each of phosphorylated cashew nut shell liquid prepolymer(PCNSL) and spindle oil was studied using a capillary rheometer over a wide range of temperatures and shear rates. The plasticizing effect of PCNSL in EPDM was evident from the progressive decrease in melt viscosity, consistency index, shear modulus and activation energy of melt flow with increase in dosage of PCNSL. The higher value of pseudoplasticity index and lower value of die swell ratio of PCNSL modified EPDM at lower temperatures and shear rates reflect probable improvement in processability during operations such as mixing and extrusion. The lower values of principal normalstress difference of PCNSL modified EPDM as against that of the unmodified EPDM indicate good compatibility between EPDM and PCNSL.

Ionic and non-ionic temperature sensitive hydrogels of poly(N-isopropylacrylamide) and calcium alginate were prepared as interpenetrating networks. Calcium alginate was used as a mould to prepare uniform, large size, spherical beads and then extracted to leave a macroporous structure. Swelling behaviour, and drug release kinetics of these thermosensitive hydrogels were studied in aqueous media. The swelling observations indicated that the equilibrium swelling degree of homopolymer gel increased after calcium alginate extraction, and besides calcium alginate had no effect on lower critical solution temperature (LCST). In addition, equilibrium swelling degree of copolymer composite hydrogels containing Na+, and Ca2+ cations were greater than that of the extracted hydrogel containing only monovalent cations. It was observed that, swelling kinetics of hydrogels followed a Fickian behaviour. Drug release experiments indicated that drug release from these hydrogels was fast and in Fickian manner.

Bricks are widely used in building construction as the most common building materials in Iran. The heavy weight of bricks accounts for the great mass of construction and thus causes more vulnerability against earthquake forces. In the present work, it is, therefore, tried to reduce the density of the bricks, as well as improve thermal insulation properties. Polystyrene foam is one of the substances that is added to the raw materials of bricks, as a pore-forming material. The effect of PSF type and its content in the mix, and also the effect of firing process temperature of the bricks on density, water absorption and compressive strength, are investigated and discussed in this paper.

Cross-linked poly(n-butyl-4-vinylpyridinium)periodate, iodate, and bromate are easily synthesized and applied as new polymeric oxidizing reagents. These reagentsare capable of oxidizing different organic compounds, such as primary and secondary benzylic alcohols to their corresponding aldehydes and ketones in an appropriate solvent. With these oxidants the oxidation of thiols to disulphides, hydroquinones to quinones, acyloins, oximes, allylic alcohols, and diols to their corresponding carbonyl compounds have also been investigated. These polymeric oxidizing agents are stable and can be easily regenerated and used.

Rapid and highly efficient synthesis of polyamides were achieved under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of 4,4í-azodibenzoyl chloride [4,4í-azobenzenedicarboxylic acid] with seven different derivatives of tetrahydropyrimidinone and tetrahydro-2-thioxopyrimidine compounds in the presence of a small amount of a nonpolar organic medium that acts as a primary microwave absorber. Suitable organic media were o-cresol. The polycondensation proceeded rapidly, and compared with the conventional melt polycondensation and solution polycondensation it was almost completed between 8-12 min giving a series of polyamides with inherent viscosities about 0.22-0.42 dL/g. The resulting polyamides were obtained in high yield and they were thermally stable. All of the above compounds were fully characterized by means of FTIR spectroscopy, elemental analyses, viscometry and solubility test. Thermal properties of the polyamides were investigated using thermal gravimetric analysis (TGA) method.