مجله ایرانی پلیمر
سال:1384 | دوره: | شماره: |تعداد مقالات:10

Thermal and rheumatic behaviors of SBR and BR are important in the curing of rubbers. In this study, thermal analysis method is used to determine the effect of carbon black (CB) loadings on the reactivity of sulphur in curing reactions, rate constants, and heat capacities of rubbers. The heat capacities of SBR and BR are modelled at different loadings of carbon black. The model is confirmed by the rheumatic studies of carbon black loadings effect on the activation energy of the curing process at different temperatures. The allylic hydrogens of BR and SBR are used to explain the rate constants and activation energies of the curing reactions. A semi empirical relation is developed for heat capacity of SBR and BR rubbers contain carbon black.

Oil-soluble and oil-water-soluble surfactants are of significant scientific and practical interest. These reagents, especially those of non-ionogenic type, are being applied widely in various areas including oil and gas industries. Non-ionogenic surfactants attract a special attention because of their high resistance to the action of mineralized media, microorganisms and shear stress. There is a continued attention in the literature about these types of compounds. Taking into consideration the above mentioned facts, several new representatives of non-ionogenic surfactants have been synthesized. They are based on propylene oxide (PO) and epichlorohydrin (ECH) i.e., epoxy compounds of a large industrial production, and such higher carboxylic acids as pelargonic, palmitic, and stearic acids as well as stearinamide. These derivatives have been synthesized by catalytic method. Their compositions and structures have been identified by physico-chemical methods. It has been shown by stalagmometric measurements that the obtained products possess high surface activity. These surfactants have been characterized by density, refractive index and by solubility in various solvents.

Eleven homopolyesters were synthesized by high temperature polycondensation of 2-(N-ethylanilino)-4,6-bis (phenoxy-2-carbonyl-chloride)-s-triazine [EAPCCT] with each of the eleven diols: Bisphenol A (BPA), bisphenol C (BPC), phenolphthalein (Ph), 1,8-dihydroxyl anthraquinone (DHA-1,8), 1,4-dihydroxy anthraquinone (DHA-1,4), resorcinol (R), hydroquinone (Hq), catechol (C), ethylene glycol (EG), diethylene glycol (DEG), and Triethylene glycol (TEG). All the polyesters were characterized by solubility, density, and viscosity measurements, and IR spectroscopy and thermogravimetric analysis methods. All these polyesters were soluble at high temperature in acetone, dimethylformamide, dimethylsulphoxide, dimethylacetamide, etc., and have reduced viscosities in the range of 0.486-0.699 dL/g in the dimethylformamide at 300C. Homopolyesters derived from 1,4-dihydroxy anthraquinone showed greater thermal stability than other polyesters.

The response mechanism of polyaniline to a selection of gases and vapours was investigated by measuring its conductance and mass changes by using four probe and elemental analysis methods, and X-Ray fluorescence (XRF) technique. Preparated films were exposed to hydrogen halides, hydrogen cyanide, hydrogen sulphide, halogens, acetic acid, mono, di, and tri-chloroacetic acid, formaldehyde , hexachloroacetone, 1,3,5-trichloromethyl benzene, methylbenzyl bromide, bromoacetone and cyanogen bromide. It is observed that the polyaniline conductance changes are partly due to two-stage sorption perhaps involving the swelling of the polymer and then gas diffusion. All the films were exposed to dilute ammonia solution or vapours organic solvents and swelled before doping, which could modify the mass and electrical measurements. It is demonstrated that slightly additional amounts of HCl gas in tested gases would significantly influence the conductivity. It was concluded that the response mechanism of polyaniline sensing different gases and vapours is due to a mixed response involving electronic and physical effects.

Novel ethylenediaminetetraacetic acid (EDTA) functionalized polyacrylonitriles (PANs) were synthesized by direct reaction of ethylenediaminetetraacetic acid dianhydride (A-EDTA) with amine and hydroxyl functionalized polyacrylonitrile. The polymeric products were insoluble in water and common organic solvents and the maximum EDTA functionality was 3.2 mmol/g. The polymer-metal complexes were prepared by dispersing of the EDTA functionalized PANs in aqueous solutions of various metal ions such as Cu+2, Ni+2, Co+2, and Cr+3 when the pH ranged from 1 to 5. The highest and lowest metal sorption were observed for Ni+2 in pH 5 and Co+2 in pH 1 which were 5.2 mmol/g and 1.5 mmol/g, respectively. The SEM micrographs show that there is a drastic variation in morphology of polymer surface when it forms complex with Cu+2. It change from rougher surface to smoother surface.

Flat-sheet hemodialysis membranes were prepared with 12% (wt) polyether sulphone (PES) and 2.8% (wt) polyvinylpyrrolidone (PVP) dissolved in dimethylacetamide (DMAc) by phase inversion method. The performances of membranes were investigated on the basis of direct removal of uremic toxins from blood serum. The membranes were put in contact with human blood serum in a batch dialyzer instrument and removal of urea, uric acid and creatinine were measured in a medical laboratory according to the standard methods. The effects of temperatures of coagulation bath and polymer solution on membrane morphology and hemodialysis performance were investigated. The SEM micrographs showed typical asymmetric channel-like structures, which their sizes and numbers change with different preparation conditions. Membrane structure depends on the diffusion rate of solvent and non-solvent molecules in the coagulation process. The temperatures of polymer solution and coagulation bath are among the most important parameters of the coagulation processes. The performance and morphology studies of hemodialysis membrane indicated that by increasing the temperature difference between coagulation bath and polymer solution temperatures, the sizes of channel- like structures were increased. A removal of 84% urea, 71% uric acid, and 53% creatinine was attained by a membrane prepared at 60°C coagulation bath and 23°C polymer solution temperatures. The L929 fibroblast cell culture test on PES membranes showed excellent biocompability.

Melt strength of polymer is one of the main primaries for the success in producing low-density extrusion foam and thermoforming process. Polypropylene (PP) as a linear polyolefin has low melt strength for bubble stabilization and sagging. Large molecules and long chain branches of PP cause higher molecular entanglements and increase elongational strength of PP melt. In this paper rheological behavior, melt elasticity, mechanical properties, and crystallinity of linear PP blends are studied and compared with blends containing a long chain branched PP resins. It is found that ternary blends of Linear PP improve the melt elasticity in a certain composition, comparing to binary blends. Branched PP resins increase molecular entanglements, which leads to higher melt elasticity. The results of this study help to understand the effects of chain size and chain architecture in increasing the melt strength and melt drawability of PP blends. These are the most important factors for producing low density PP foam and high quality thermoformed products.

Organic - inorganic hybrids were prepared using 3-glycidoxypropyl-trimethoxysilane (GPTMS) and bisphenol A (BPA) as a cross-linking agent, via the sol-gel process. The cross-linking agent was used to prevent brittleness and the formation of cracks in hybrid coatings. Attenuated total reflectance infrared (ATR-IR) spectroscopy technique was used to characterize the structure of the hybrids. The morphology of the hybrid coatings was examined by scanning electron microscopy and Si mapping. The hybrid systems have a uniform network structure and inorganic phases have a size of less than 100 nm. In addition, the effect of BPA/GPTMS molar ratio on coss-linking and corrosion protection properties of hybrid coatings was investigated by ATR-IR and corrosion resistance evaluation test methods (linear sweep voltametry (LSV) and 2000-h salt spray test methods). The results of these experiments shown that the increasing of cross-linking between silica-network and BPA would prevent the formation of crack and decrease brittleness. Increasing BPA content in organic-inorganic hybrid coatings or nanocomposite Lead to the formation of an efficient barrier to water and corrosion initiators such as chloride and oxygen.

The adhesion and tackiness of cosmetic patches are very important factors, especially when the patches are applied to an area with sensitive skin, such as face. The objective of this work is to study the influence of varieties of alpha hydroxy acids concentration as ingredients of cosmetic patches on their tackiness. Different amounts of two cosmetic patch ingredients, glycolic acid(GA) and lactic acid(LA), were mixed thoroughly with solution of an acrylic pressure-sensitive adhesive (PSA). Films with 32 µm thickness were prepared by casting formulations on a polyethylene terphethalate film. Tack test was carried out on different formulations according to ASTM D3121-94. It was observed that tack value increase by increasing LA concentration up to 6% (w/w). Tack value increase also, by increasing GA concentration upto 1% (w/w), then it decrease by increasing GA concentration up to 3% (w/w), and then increase again by increasing GA concentration above 6% (w/w). These results are due to changes in entanglements, glass transition temperature, plateau modulus Go of adhesive, and functional groups that exist in additives.

A Monte Carlo approach based on kinetic gelation model is used to simulate the kinetics of non-linear free radical copolymerization of vinyl-divinyl monomer mixture or chemical gelation, and to characterize kinetic effects on polymerization statistics and microstructures. New algorithm for random selection of the next neighbour site in a self-avoiding random walk and efficient mechanisms of mobility of components are introduced to improve the universality of the predictions by removing commonly occurring simulation deficiencies due to early trapping of radicals. The model has the capability of predicting the onset of the sol-gel transition, and the effect of chemical composition on the transition point. It is shown that it is attain a better understanding of microstructure evolution and appearance of gel phase during polymerization and chemical gelation. Finally, an important benefit of the simulation method is its ability to characterize the system in which, the dominant combination reaction leads to highly branched structure.