فهرست مطالب

Iranian polymer journal
Volume:15 Issue: 6, 2006

  • تاریخ انتشار: 1385/06/11
  • تعداد عناوین: 8
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  • Massoumeh Bagheri, Reza Zahedi Rad Page 447
    Effects of bismaleimide (BMI) resin on dielectric properties e.g., permittivity (e''), loss factor (e"), and ionic conductivity (σ) of two different epoxy-amine resin systems were measured during dynamic curing (over a temperature range 20-300°C) by using dielectric analysis (DEA). Dynamic mechanical properties, e.g., flexural storage and loss moduli (E'' and E") and shear storage and loss moduli (G'' and G") of the glass-fabric reinforced composites (laminates) of the above mentioned resin matrices were carried out by dynamic mechanical analysis (DMA) technique. Double exothermic curing peaks were observed for the formulations with DDS as curing agent. For each system, that region of the curve in which the values for ionic conductivity are frequency dependent, indicates that the measurement is strongly influenced by dipole relaxations. At temperatures near or below Tg, dielectric properties of resins are dominated by the molecular dipoles (frequency-dependent response). Ionic conductivity increases largely on using DDS as curing agent for DGEBPA over MDA however; addition of BMI to DDS- and MDA-cured thermosets decreases the ionic conductivity in the former and increases it in the later resin systems. Addition of bismaleimide (BMI) resin in three different concentrations tothe glass-fabric DGEBPA/MDA and DGEBPA/DDS laminates, increases Tg, Tg∞, and flexural and shear storage moduli (E'' and G'') considerably.
  • Elaheh Kowsari, Shadpour Mallakpour Page 457
    N,N′-(4,4′- Oxydiphthaloyl)-bis-L-leucine (4) was prepared as an aliphatic optically active diacid monomer from treatment of 4,4′-oxydiphthalic anhydride (1) with L-leucine (2). The direct polyesterification reaction of this diacid with several commercially available aromatic diols was performed in a system of thionyl chloride and pyridine (Py). Polycondensation was carried out by varying the initial reaction time of thionyl chloride, Py, and diacid (aging time), the reaction temperature, and the time of heating. A series of optically active poly(ester-imide)s (PEI)s were obtained in high yield and inherent viscosities under optimum conditions. All of the above polymers were fully characterized by 1HNMR, FTIR, elemental analysis and specific rotation techniques. Some structural characterization and physical properties of these optically active PEIs are reported. The resulting PEIs show good solubility and thermal stability.
  • Mohammad M. Ranjbaran Page 467
    Potassium persulphate (KPS) has been used as efficient initiator for graft copolymerization of the ethyl acrylate (EA) onto hydroxypropyl methylcellulose (HPMC) at 60 ± 0.1°C. Graft copolymerization of EA onto HPMC has taken place through the radical initiation process. The grafting parameters have been evaluated by varying concentration of EA from 0.097 to 0.376 mol/L, KPS from 1.772 to 5.316 mmol/L and HPMC from 0.117 to 0.468 mmol/L. Evidence of grafting was obtained from IR spectroscopic measurements, SEM, and TGA studies of the grafted and ungrafted HPMC. The rate of graft copolymerization has shown 1, 0.5, 0.5 order with respect to the concentrations of the EA, KPS, and HPMC, respectively. The graft copolymerization data obtained at different temperatures were used to calculate the energy of activation which has been found to be 41.7±1.2 kJ/mol within the temperature range from 50 to 65°C. On the basis of the experimental observations, initiating steps have been proposed and a suitable rate expression for graft copolymerization has been derived.
  • Yongshen Xu, Lili Wang Page 477
    The synthesis and characterization of new liquid crystalline polyesters havebeen described containing symmetrically di-substituted hydroquinone monomer.2,5-Bis(4-hexyloxybenzoyloxy) hydroquinone (HQ6) and1,6-bis(4-hydroxybenzoyloxy) hexane (H6) monomers were synthesized via multi-steproutes from 2,5-dihydroxyquinone and in one step route from 4-hydroxybenzoic acid, respectively. Copolyester PHQ6-co-PH6 was synthesized through high temperature solution polymerization of HQ6 and H6 diols with terephthaloyl chloride. The homopolyesters PHQ6 and PH6 were also synthesized from respective monomers with terephthaloyl chloride by the same method. The molecular weights of polyesters containing the disubstituted hydroquinone units were not very high due to the sterichindrance of the bulky substituting groups on the hydroquinone HQ6 monomer. The homopolyester PHQ6 was soluble in common organic solvents, whereas solubility decreased for copolyester due to decreased content of end hexyloxy groups. Liquid crystalline properties were determined by differential scanning calorimetery (DSC) and polarizing optical microscopy (POM) techniques. The effect of the rigid lateral moieties on the thermal properties and liquid crystallinity was investigated on the prepared copolymer and it was compared with that of the analogous homopolyesters. Optical microscopy images showed Schlierene texture characteristic of the nematic phase for both polyester and copolyesters. The DSC experiments were also in accord ance with mesophase formation. The melting points and glass transition temperature values of PHQ6 and PHQ6-co-PH6 were significantly higher than those of the PH6 homopolyester. All of the obtained compounds were characterized by conventional spectroscopic methods.
  • Ismet Kaya, Suleyman Culhaoglu Page 487
    In this study, the conditions of oxidative polycondensation reaction of 4-(4-nitrobenzylideneamino)phenol (4-NBAP) were studied using oxidants such as air (O2), H2O2, and NaOCl in an aqueous alkaline medium of 50-90°C. Poly(4-(4-nitrobenzylideneamino)phenol) (P-4-NBAP) was characterized by 1H and 13C NMR, FTIR, UV-vis, size exclusion chromatography (SEC), and elemental analysis techniques. The solubility of oligomer was investigated by using organic solvents such as dimethylformamide, tetrahydrofurane, dimethylsulfoxide, methanol, ethanol, CHCl3, CCl4, toluene, acetonitrile, ethyl acetate. According to air (O2) oxidant (flow rate 8.5 L/h), the conversion of (4-NBAP) was 50.83% in optimum conditions such as [4-NBAP]o = [KOH]o = 0.05 mol/L at 60°C for 10 h. According to the SEC analysis, the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of P-4-NBAP were found to be 11109, 12886 g mol-1 and 1.160 using air (O2); 17517, 23402 g mol-1 and 1.336 using NaOCl; and 8960, 10653 g mol-1 and 1.189 using H2O2, respectively. Also, thermogravimetric analysis showed poly(4-(4-nitrobenzylideneamino)phenol) is stable against thermal decomposition. The weight loss of P-4-NBAP was found to be 49.23% at 1000°C.
  • Hassan Namazi, Mojtaba Abbasian, Habibollah Baharvand, Ali Akbar Entezami, Ali Ghaderi, Sohrab Rahmani Page 497
    Concentrated emulsion polymerization was used for the synthesizing of crosslinked polystyrene-divinylbenzene (PS-DVB) containing 10% (X-10) and 16% (X-16) DVB with pore size less than 10 μm. For application of these resins as columns’ filler in ion-exchange chromatography; chloromethylation and then amination processes were performed via aqueous trimethylamine. The chloromethylation reactions was done by 1,4-bis(chloromethoxy) butane in dichloromethane and in the presence of stannic chloride as catalyst at 0°C. The exchange capacities of anion exchange resins X-16 (CE=3.5 meq/g) and X-10 (CE=3.8 meq/g) was determined by titration procedure. The structure of PS-DVB was investigated by scanning electron microscope (SEM) technique. The SEMimages showed that the porous structure of PS-DVB resin was approximately maintained intact after chloromethylation and amination reactions. TGA and FTIR techniques were used to investigate the thermogravimetric analysis and structures of obtained resins, respectively.
  • Hemant S. Patel, Keshav C. Patel Page 505
    Various copolyamides were synthesized using high temperature polycondensation technique from 2-(N-ethyl anilino)-4,6-bis(phenoxy-2-carbonyl chloride)-s-triazine [EAPCCT] and various mixtures of diamines such as; (p-phenylene diamine [PPDA]+4,4''-diaminodiphenylamide [DADPA]), (PPDA+4,4''-diaminodiphenylsulphonamide [DADPSA]), (ethylene diamine [EDA]+DADPA), (EDA+DADPSA), (EDA+1,4-diamino toluene [DAT]) etc. They were characterized by density and viscosity measurements, FTIR and NMR spectroscopy, techniques solubility tests and thermogravimetric analysis method. Density of different copolyamides was in the range of 1.155-1.232 g/cm3. Reduced viscosity was in the range of 0.430-0.386 g/dL that indicates the fairly higher molecular weight rangeof the synthesized polymers, which is required for the polymer to possess reasonablygood mechanical and thermal properties. All the polymers synthesized showed moderateto high thermal stability required to be categorized as high performance materials.
  • Ebrahim Vasheghani, Farahani, Fatemeh Sarvi, Sameereh Hashemi, Najafabadi, Mostafa Moin, Zahra Pourpak, Syed Abbas Shojaosadati Page 525
    In the present study, the optimum conditions were determined for PEGylation of human red blood cells by methoxypoly(ethylene glycol) (mPEG) with molecular mass of 5 kDa, activated by succinimidyl carbonate. Factorial and Taguchi design methods for experiments were used to study the effects of process variables on coating of the cells and determine the optimum conditions for PEGylation. The inhibition of agglutination by a blood-type specific antiserum (anti-D) was employed to evaluate the effect of the polymer coating. The remaining single cells after incubation with anti-D sera were counted using a simple hemocytometer (Improved Neubauer Ruling). The extent of surface coating was evaluated by attachment of cells to FITC labeled-anti-D serum and recording as the fluorescence intensity ratio of FITC-anti-D bound cells of the PEG-RBCs versus control (uncoated) RBCs. The morphology of red blood cells was determined by scanning electron microscopy (SEM) technique. Statistical analysis of experimental design together with SEM results showed that the optimum conditions were pH = 8.7, T=14°C, and t = 60 min while the suitable polymer concentration was found to be 12 mg/mL.