مجله ایرانی پلیمر
سال:1380 | دوره: | شماره: |تعداد مقالات:7

1-(2-Pyrrolyl)-2-(2-thienyl)ethylene (PTE) and 2-(2-thienyl) pyrrole (TP) were synthesized via Wittig and cyclization reactions. The electropolymerization of pyrrole (PY) and N-methylpyrrole (NMP) in the presence of catalytic amounts of PTE and TP have been studied by the cyclic voltammetry method. The obtained polymers showed considerable increase in the electroactivity and redoxability. The presence of PTE and TP during electropolymerization of NMP and PY lead to the increase in the rate of polymerization and decrease in the applied potentials. The electrochemical behaviour of produced polymers is described and an interpretation of the results is given.

Powdered vulcanized rubber waste generated in a factory was examined as a compounding additive in natural rubber compounds and in blends of natural rubber and styrene-butadiene rubber. The cure characteristics were evaluated with the Monsanto Oscillating Disc Rheometer while tensile sheets were prepared and stress-strain measurements in simple extension were used to characterize the mechanical properties of the vulcanized elastomers. In all the vulcanizates examined, the incorporation of rubber waste resulted in a slight deterioration of properties. The deterioration of properties is attributed tQ the poor interfacial bonding between the rubber waste and the virgin matrix elastomer. Also, it was found that at low volume loading, the vulcanized waste has no adverse effect on vulcanizate properties.

Due to various components present in the Ziegler-Natta catalyst system and different interactions, taking place between them during the preparation and polymerization, studying of the system is usually very difficult. In this study mono- and bi-supported catalyst systems Of MgCl2 (ethoxide type)/TiCl4/ID and SiO2/MgCl2 (ethoxide type)/TiCl4/DNBP were prepared for the polymerization of propylene, whilst for polymerization of ethylene, MgCl2 (ethoxide type)/SiO2/TiCl4 was prepared. Di-n-butyl phthalate (DNBP) and diisobutyl phthalate (DIBP) were used as internal donors (ID), whilst triethylaluminium (TEA) was used as the cocatalyst. Structural study was carried out using FTIR, SEM, XRF and BET techniques. The observed shift in vibration of C=O, and C-O bands of the electron donors indicate some interactions between the donors, support and the catalyst itself. Surface area of the mono-supported catalyst having the electron donor and bi-supported catalyst without electron donor were about 230 m2/g. For the bi-supported having DNBP as the donor, however, a value of 177 m2/g was obtained. SEM study shows that the spherical morphologies Of SiO2 are replicated on catalyst and to a lesser extent on final polyethylene obtained. Dimethoxymethyl cyclohexyl silane (DMMCS) was used as an external donor for the polymerization of propylene.

Highly sulphonated melamine-formaldehyde resin (HSMF) is prepared by atmospheric reflux from melamine, formaldehyde, sodium sulphite and metabisulphite through-a four-step reaction. The sulphite/melamine molar ratio between 1.0-2.0 and the formaldehyde/melamine molar ratio varied between 3.0 and 5.0. The effects of degree of sulphonation and F/M ratio on the fluidity of resin solutions were studied. The F/M ratio is directly and S/M ratio is inversely proportional to viscosity of the resin solution. Because of lower viscosity of HSMF resins than that of SMF resins, it is expected to be more effective superplasticizer in cement sand mortar. The results show that viscosity of the solutions increases with increasing MW of the polymers until a critical molecular weight, beyond which there is a rapid increase in viscosity due to formation of a hexagonal close-packed system.

Oily sludge accumulates in large quantities as waste in petroleum refineries. Disposal of this waste is a difficult problem in the overall waste treatment management programme of refineries. Since this sludge contains about 70 % hydrocarbons, it was thought worthwhile to try this as a substitute for processing oil in the compounding of rubber blends. The sludge was first purified and different mixes containing varying concentrations of the conventional processing aid namely aromatic oil and the refinery sludge were prepared. The processability of the mixes was studied in a Brabender Plasticorder. The cure characteristics of the mixes were evaluated and the vulcanizates were tested for various physical properties and cross-link density including ageing. The processing characteristics showed that rubber blends could be processed with sludge just like the other conventional processing oils. It was found that, on complete substitution of aromatic oil with sludge, the optimum cure time reduced significantly and the tensile properties exhibited some improvement. Since sludge is a waste material from oil refineries, posing disposal problem, which is a pollutant to environment due to open dumping, its utilization as processing oil in rubber compounding can be a simple practical method of disposal in a useful manner.

This paper concerns non-linear state estimation in a batch polymerization reactor where suspension polymerization of methyl methacrylate takes place. A kinetic model proposed in bie literature is selected and its validity has been verified through an experimental set-up. Based on this model monomer conversion and average molecular weights of the polymer are estimated using only one output measurement (reactor temperature). The performance of the estimator, which has the structure of an extended Kalman filter, is examined through simulation and experimental studies in the presence of different levels of parameter uncertainties. The effects of adding "fictitious noise" and parameter state" to the estimation algorithm are also investigated. To find the best fictitious state, the main parameters of polymerization model are divided into three groups. The parametric study of the MMA polymerization model indicates that, when the source of parameter uncertainty is unknown, the best selection of parameter state is the initial mass of monomer.

The cyclicvoltammetry method was utilized for the determination of percolation threshold of electroactivity of polyvinylchloride (PVC) and doped polyaniline through sulphosalicylic, acid (SSA) blend. The blends were prepared from N-methylpyrrolidone (NMP) solutions and PVC/PANI-SSA blend with weight fractions from 0.1 to 0.006 of polyaniline. The films from the blends were provided by. casting the above polymer solutions on a GC electrode. Voltammograms were recorded by using a one-compartment cell fitted with a GC as working electrode, Pt as auxiliary electrode and SCE as reference electrode, in 1M perchloric acid electrolyte solution. The obtained results from cyclicvoltammetry showed that PANI-SSA/PVC on and above 0.008 percent weight from polyaniline is electroactive.