Iranian Polymer Journal
Year:2006 | Volume:15 | Issue:5 (71)|Papers Count:10

Wool and nylon 6 knitted fabrics were dyed using three commercial direct dyes which are suitable for nylon and wool fabrics. The dyed samples were aftertreated, using two different syntans and full backtan. When all dyeings were subjected to two consecutive ISO CO6 wash tests, it was found that all aftertreatments provided an improvement on wash fastness. However  aftertreatment of the dyeing using full backtan, improved wash fastness to the greater extent than commercial and synthesized syntans. This improvement for C.I. Direct Yellow 12 is higher, since this dye belongs to class A, which has low wash fastness property; thus, the full backtan in this case is more effective. Although the full backtan is effective in improving the wash fastness of direct dyes on nylon 6 and wool, but, the aftertreatment is rarely used owing to the toxicity of potassium antimony tartarate because it can impair the handle and the light fastness of dyeing as well as impart a shade change in dyeing. An aftertreatment with a syntan has mostly replaced the full backtan as a means of improving the wash fastness of direct dyes on nylon 6 and wool. Syntans offer the advantage of being applied in single stage process and do not suffer from the disadvantage displayed by their natural counterpart, however it is generally accepted that an aftertreatment with a syntan is not as effective as an aftertreatment with the full backtan.

Alternating copolymerization of carbon monoxide (CO) with styrene (ST) or p-ethylstyrene (EST), catalyzed by the transition metal Pd (II) complexes, was carried out. The kinetics of alternating copolymerization of ST and EST with CO was investigated. The results show that the copolymerization temperature has a sensitive effect on the copolymerization rate and the catalytic activity in the ST and CO copolymerization system. The copolymerization rate increases with the increase of reaction temperature from 55 to 67°C, and then decreases with further increasing the reaction temperature up to 70°C. The variations of the copolymerization rate with the initial CO pressure were also studied, and the results indicate that initial copolymerization rate increases with decreasing the CO pressure in gas phase. Moreover, the semicontinuous experiments performed at different reaction conditions further confirm that lower CO pressure benefits the copolymerization rate. The structure of EST/CO copolymer was verified by means of Fourier transform infrared (FTIR), elemental analysis (EA), 1H NMR, and 13C NMR methods. The characteristic results indicate that the EST/CO copolymer prepared from p-ethylstyrene and carbon monoxide in the presence of palladium (II)/2,2'-bipyridyl catalyst is an alternating copolymer. It is interesting to note that there is a higher initial copolymerization rate under proper lower CO pressure in the EST/CO system, which is similar to that in the ST/CO system. In addition, comparing with two systems, there are higher catalytic activity and shorter catalytic life in the EST/CO system than those in the ST/CO system. The different copolymerization rates between EST/CO and ST/CO systems are attributed to the different nature of  a-olefins.

An investigation is conducted into the non-isothermal kinetics of the curing reaction of diglycidyl ether of bisphenol A (DGEBA) epoxy resin with two novel aromatic diamines, 4,4´-diaminostilbene (DAS) and 4,4´-diaminoazobenzene (DAAB), as curing agents. Kinetics analysis of the curing reaction of DGEBA with two different concentrations (29 wt% =0.13 mol% and 19 wt%=0.09 mol%) of the curing agents was studied using non-isothermal differential scanning calorimetry (DSC) technique. Two methods (Ozawa and Kissinger) for analysis of the scanning DSC data were applied to calculate the kinetic parameters and compared with kinetic parameters obtained from isothermal DSC tests using Kamal method. Activation energies in the range of 52.5-59.5 kJ/mol were obtained for both DGEBA/curing agent systems. The water absorption and resistance of the cured products against solutions of H2SO4 and NaOH were also studied. Water uptake curves for both systems are similar. Weight loss for the cured products of DGEBA/DAS and DGEBA/DAAB systems in 50% solution of NaOH reached the equilibrium values of 0.2% and 0.5%, respectively after about 80 h and weight gain of the cured products of both systems in 30% solution of sulphuric acid reached the equilibrium value of about 0.3% after about 40 h. The cured products from DGEBA/DAS system showed less weight loss during thermal degradation at 250°C but their water uptake was much higher.

Synthesis and characterization of new liquid crystalline poly(N-substituted urethane) s using 4-bromo-(4-hexyloxy-biphenyl-4'-oxy)butane (C6-C4Br) as mesogenic pendant group is described. The liquid crystalline polyurethanes were synthesized through N-substitution by a two-step process. First the polymer was dehydrogenated by sodium hydride, and then the prepared urethane polyanion was treated with C6-C4Br. The chemical structures were characterized by FTIR, 1H NMR, and elemental analysis. The solubility and thermal properties of N-substituted polyurethanes were investigated in view of the N-substitution degree of mesogenic unit. Thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC) in combination with polarizing optical microscopy (POM) were used to investigate the thermal properties of N-substituted polyurethane. As the degree of N-substitution increased, the solubility of polyurethane decreased in common organic solvents, and thermal stability increased from 285°C to 370°C because of different thermal-degradation mechanisms of parent and N-substituted polyurethanes. The glass-transition temperature (Tg) was shifted to higher temperature with an increasing degree of substitution due to the increasing rigidity of polymer chains. Optical microscopy showed focal conic texture characteristic of the smectic A phase for both C6-C4Br and N-substituted polyurethanes. DSC Experiments were also found in accordance with mesophase formation. The liquid crystalline properties were strongly dependent on the N-substitution degree with increasing mesogen content from 25 to 100%, the mesophase-transition and isotropization temperature increased. The minimum 25% amount of mesogen is necessary to exhibit a liquid crystal property in the polymer.

PVC is one of the world’s major polymers and a large amount of PVC is produced worldwide for its superior mechanical and physical properties. Graft copolymerization of PVC with monomers such as styrene has been examined to improve the thermal stability of PVC. This graft copolymerization was carried out by atom transfer radical polymerization (ATRP). In this method PVC was condensed with toluene in mild condition (toluene as arylating agent, AlCl3 complexed with nitrobenzene as catalyst and THF as diluent) and we used arylated PVC (PVC-ph) as a starting polymer and N-bromosuccinimide as a brominating agent to obtain polymers with bromine group. This brominated PVC was used as a macroinitiator. This macroinitiator can polymerize styrene in the presence of CuCl/bpy catalyst system in THF solvent at 90°C. The formation of the graft copolymer was confirmed with GPC, DSC, 1H NMR and FTIR spectroscopy. This approach using a macroinitiator is an effective method for the preparation of new materials.

Swelling behaviour is one of the important properties of hydrogel-based drug delivery systems, which always affects the diffusion of solvent into and release of drugs from drug loaded microcapsules. In this study, the swelling behaviour of alginate-chitosan beads at acidic and basic conditions, to simulate gastric and intestinal media, were investigated. Spherical hydrogel beads were prepared by addition of aqueous sodium alginate and alginate-N,O-carboxymethyl chitosan (NOCC) solutions into CaCl2 solution. These hydrogel beads were then transferred into a chitosan solution to obtain chitosan coated beads. The effect of concentration of calcium chloride, residence time for ionic cross-linking, concentration of chitosan, addition of NOCC into alginate solution, coating of alginate-NOCC by chitosan as well as drying method on the swelling behaviour of the alginate-chitosan beads was studied. It was found that swelling degree of the air-dried and chitosan coated beads was lower than that for freeze-dried and uncoated beads, respectively. In addition, the presence of NOCC in the network resulted in reducing swelling of hydrogel beads. Swelling degree of hydrogels in basic media (pH 7.4) was also much higher than that in acidic media (pH 1.2). Thus, alginate-NOCC-chitosan beads are good candidate to be studied as colon-specific drug delivery systems.

It was recently reported that water-soluble conducting polyaniline may be prepared using a new template-guided enzymatic approach. It was found that the template provides a necessary type of local environment where the pH and charge density near the template molecules are different from that of the bulk solution. A strong acid polyelectrolyte, such as sulphonated polystyrene (SPS), is the most favourable because it provides a lower, local pH environment that serves to both charges and preferentially align the monomers through electrostatic and hydrophobic interactions to promote the desirable head-to-tail coupling. Poly (acrylic acid) (PAA) partial sodium salt is used as an acid polyelectrolyte in this work. Biocatalytic polymerization using a naturally occurring enzyme is advantageous because it is a simple, one-step and environmentally compatible method. The horseradish peroxidase (HRP) enzyme is used in polymerization of o-toluidine in the presence of poly (acrylic acid) partial salt as a template and camphor sulphonic acid as a dopant. The synthesis is simple and the conditions are mild. Best results are obtained in pH 4.3 phosphates buffered aqueous solutions with stoichiometric amount of monomer, template and oxidant and catalytic amount of enzyme. The synthesized polymers have been characterized by UV-vis and FTIR spectroscopy and cyclic voltammetry. These studies confirm that electroactive and conducting forms of poly (o-toluidine) (POT) are obtained in the presence of PAA.

The cure reaction for a system of o-cresol-formaldehyde epoxy resin (o-CFER), with 3-methyl-tetrahydrophthalic anhydride (MeTHPA), N,N-dimethyl-benzylamine, and organic montmorillonite (org-MMT), as a curing reagent, an accelerator and an additive, respectively, was investigated by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The XRD result indicates that an exfoliated nanocomposite was obtained. The curing kinetic data of o-CFER/MeTHPA and o-CFER/MeTHPA/org-MMT nanocomposites were obtained by non-isothermal differential scanning calorimetry. The nanocomposite has a slightly higher average value of activation energy than that of pure o-CFER due to the epoxy resins chains are inserted into the galleries of montmorillonite and the movement and diffusion of reactive groups are hindered. The curing kinetics analysis was performed by the isoconversional methods of Ozawa, Friedman, and Kissinger-Akahira-Sunose. The results showed that the Ozawa method is the best of the three models studied.

In the present study, the linear low-density polyethylene (LLDPE)/ZrO2 nanocomposites were synthesized via in-situ polymerization with rac-Et(Ind)2ZrCl2/MAO catalyst. First, the nano-ZrO2 filler was impregnated with the desired amount of MAO. Then, copolymerization of ethylene/1-octene was performed in the presence of nano- ZrO2/MAO filler to produce the LLDPE/ZrO2 nanocomposites. The amounts of nano- ZrO2 filler employed were varied at 0.1 and 0.3 g corresponding to [Al]MAO/[Zr] ratios=1135 and 3405, respectively. It can be observed that the polymer yield increased with increasing the ratios of [Al] MAO/[Zr]. However, the observed polymer yields were much lower (about 5-30 times) compared to the yield with no filler addition. The filler contents in polymer were in the range of 23-25 wt%. The characteristics of LLDPE/ZrO2 nanocomposites obtained were determined by means of DSC, SEM/EDX, TEM, 13C NMR, and XPS. It was observed that the LLDPE/ZrO2 nanocmposites exhibited slightly lower melting temperature (Tm) and crystallization temperature (Tc). SEM Micrographs demonstrate the homogeneous matrix of the samples. In addition, with EDX mapping technique, it was also revealed that the nano-ZrO2 filler was well distributed over the polymer matrix. Based on the TEM result, it was also revealed that the smaller and more uniform particles can be observed after polymerization. These observations suggested that the fragmentation of nano-ZrO2 particles or segregation of the secondary particles could occur resulting in good dispersion of the particles. The distribution of comonomer was studied by 13C NMR. It was shown to be random as seen in the similar catalytic system without filler addition. The binding energy (BE) for C 1s obtained from XPS to be 285.7 eV indicating no significant change in the polymer microstructure with the addition of nano-ZrO2 filler.

The existence of interfacial instability at the interface of multilayer polymeric fluid is well known. The experimental studies have shown that interfacial instability of two-layer polymer melts plays an important role in polymer processing operation. This work is designed mainly to provide guidelines for the development of experimental techniques for the improvement of the two-layer polymer products in the polymer processing industry. This is done by performing a series of tensile tests on extruded two-layer polymer melts in order to get insight into the relation between interfacial instabilities and mechanical properties of polypropylene (PP) over high density polyethylene (HDPE) systems. Observed variations of the mechanical properties have been related to the conformation of the interfacial wave. Thus, a relationship is established between the interface morphology corresponding J to extrusion instabilities and the mechanical characteristics of the interfacial strength, of the extruded PP/HDPE.