Iranian polymer journal
Volume:12 Issue: 3, 2003

The thermooxidative degradation of polytetrafluoroethylene (PTFE), both pure and containing additives such as: carbon (graphite) (C), bronze (BZ) and glass fibre (GF), has been studied by non-isothermal thermo-differential analysis (DTA). The values of kinetic parameters obtained from the DTA data, on the basis of thermo-kinetic equations, were compared with the values obtained from the non-isothermal thermogravimetric analysis (TG-DTG) and a good agreement was achieved. The analysis of the characteristic temperatures and of the kinetic parameters from DTA-DTG data revealed that the thermal stability and mechanism of thermooxidative degradation depend on the nature and concentration of additives. The results were confirmed by the existence of a real compensation effect. The following equation was derived for the compensation effect: ln A = 0.1410 E - 0.15.

In this research the effect of several parameters such as weight percent, length, distance and orientation of carbon fibres on microwave attenuating of polymeric coatings have been investigated and microwave attenuating behaviour of these composite coatings were evaluated in frequency range of 8-12 GHz (X-bond). The optimum length of carbon fibres was found to be about one-half of the wavelength of incident radiation. The results show that attenuation is increased by increasing the weight percent of carbon fibres up to the area limitation effect. The best orientation of the carbon fibres is multidirectional orientation.

In this work, blends with different ratios of thermoplastic polyurethane-polypropylene (TPU-PP) were prepared using a Haake internal mixer and studied by SEM micrographs of cryofractures. The polymers, their blends and PVC blood bag were characterized by measuring their mechanical properties (modulus, tensile strength and elongation- at-break), water absorption and blood compatibility. According to the obtained results, although the blends are immiscible, the mechanical properties of the blends except TPU/PP = 50/50 are comparable with commercial blood bag material. Results showed that the physical properties of TPU/PP = 80/20 blends are nearly similar or even better than those of PVC blood bag. The comparison of behaviour of platelet adhesion onto the surface of the best sample (TPU/PP = 80/20 blend) with the commercial blood bag surface showed the less tendency of the blend than the second one to interact with platelets.

In this article various blends of polyvinylchloride (PVC), polypropylene (PP) and highdensity polyethylene (HDPE) were prepared. Mechanical properties and morphology of the samples were investigated. Then hydrolyzed paper was added and for improvement of impact strength of the blends about 10 wt% ethylene-propylene-diene copolymer (EPDM) was used. The results show that EPDM improves the impact strength of the blends. The mechanical properties and morphology of various blends of PP/HDPE/PVC/EPDM/paper with 2 wt% calcium stearate (CS) were studied. We concluded that compositions 4.8/43.2/10/10/30 and 38.4/9.6/10/10/30 (w/w) had better impact strength than other blends. The blends with waste materials were also prepared by the same ratios. They also showed better impact strength than PP/HDPE blends. These blends can be used as artificial wood.

Copolymers of isobutylmethacrylate (i-BMA), and laurylmethacrylate (LMA), were prepared by solution free radical copolymerizations at 70°C using 2,2’-azobisisobutyronitrile,as initiator. The synthesis of these copolymers were investigated over a wide composition and conversion range. Copolymer compositions were determined as a function of conversion from the %C, %H, and %O contents of copolymer by elemental analysis. In order to avoid the complications of copolymerization kinetics, the “pseduokinetic rate constant method” (PKRC) was applied to constant and variable volume polymerization system. Theoretical values of coupled parameter kp / k0.5 t calculated from the “implicit penultimate unit effect” model (IPUE) based on instantaneous monomer feed composition, were determined from Meyer-Lowery integrated copolymer composition equation. The results have been compared with experimentally determined kinetic parameters.

The effect of silane coupling agent on the peel strength of copper/prepreg/copper composites was investigated. The composite consisted of one or two sheets of prepregs covered by two copper plates. The prepreg was prepared by hand drylay- up technique using an epoxy resin and an electrical resistant glass fabric (E-glass style 2165). 4,4’-Methylene dianiline (MDA), an aromatic amine, was used as curing agent. Curing times for prepreg and composite at 120°C and 170°C were 15 min and 1h, respectively. γ -Aminopropyl trimethoxy silane (APTS) was used as coupling agent. The effect of APTS on the adhesion of epoxy/glass and epoxy/copper interfaces was investigated by two methods. In the first method, the surfaces of the glass fabric and/or the copper plates were treated by APTS. In the second method, APTS was directly added to epoxy resin. In addition, the effect of additional resin on the adhesion strength was also studied by the latter method.

Aphotocurable dental ionomer liquid has been prepared via the reaction of acrylic/itaconic acids copolymer (2:1) with acryloyl chloride as the coupling compound. It is then treated with proper amounts of H2O and 2-hydroxyethyl methacrylate (HEMA) as the co-solvent followed by camphorquinone as the initiator and trisodium hydrogen phosphate as the modifying agent, which resulted in the formation of a photocurable ionomer liquid. The working time as well as compressive and diametral tensile strengths of the setting cement, after treating the liquid with the reactive powder, were measured and compared with those of a conventional liner brand cement. It was foundthat for setting time of 20 s, the working time and diametral tensile strength were higher than those for the conventional cement, but the compressive strength was almost the same.

The polymerization of butadiene with catalytic dithiosystems, based on organic dithio derivatives of Ni or Co and organoaluminium compounds was studied. It was shown that these catalytic dithiosystems provide the preparation of the lowand high-molecular weight 1,4-cis-polybutadienes; high-molecular weight 1,4-cis + 1,2- and syndiotactic 1,2-polybutadienes with high activity. The effect of nickel or cobalt and monomer concentration, Al:Co ratio, temperature, polymerization time on conversion, stereoregularity and molecular weight in the butadiene polymerization by nickel- and cobalt-containing dithiosystems was studied. The regularities of interrelated changes of polybutadiene microstructure and molecular masses in synthesis in the presence of nickel- and cobalt-containing dithiosystems have been investigated and explained.

Anew N-substituted polyaniline is synthesized by insertion of a polyether chain in the form of Triton X-100 onto the polyaniline backbone. In the preparation method, firstly the emeraldine base polyaniline was reacted with NaH to produce the Nanionic doped polyaniline and then contacted with chlorinated Triton X-100. The prepared N-substituted polyaniline was characterized by UV-vis, FTIR, 1H NMR spectroscopy techniques and elemental analysis. The physical properties of synthesized polymer such as electrical conductivity, thermal and electroactivity properties were also studied. The prepared polymer has good solubility in common organic solvents such as THF and chloroform.

Different amounts of two skin permeation enhancers, oleic acid (OA) and propylene glycol (PG), were mixed thoroughly with solution of an acrylic copolymer pressure sensitive adhesive (PSA). Films with different adhesive layer thicknesses (30 and 60 μ) were prepared by casting of the mixed solutions with a film applicator on PET 80 μ films followed by drying of solvents. The results of peel test were explained on the basis of changing of entanglement molecular weight (Me) of the copolymer and its miscibility with the enhancers. PG concentration had no significant effect on the peel strength. This is related to a constant amount of Me, resulting from hydrogen bonding between PG and the copolymer. The presence of OA decreased the peel strength, specially when concentration exceeded 5(w/w%). This decrease can be related to the formation of a weaker surface layer in addition to the diminution of the adhesive effective thickness. A two fold increase in the thickness had no effect on the peel strength of OA samples. This shows that at least one half of the thickness of 60 μ samples is ineffective in viscoelastic energy dissipations in the copolymer. Cohesive failure for 30 μ samples occurred, when OA concentration exceeded 15 (w/w%). However, this failure was observed above 10 (w/w%) for 60 μ samples, because the applied force is not transferred through the ineffective thickness to the backing layer.