Iranian polymer journal
Volume:12 Issue: 1, 2003

Several homopolyesters were synthesized by high temperature polycondensation of 2-(N-piperidino)-4,6-bis(naphthoxy-2-carbonyl chloride)-S-triazine [PNCCT] with each of the eleven diols: bisphenol-A (BPA), bisphenol-C (BPC), phenolphthalein (Ph), 1,5-dihydroxy anthraquinone (DHA-1,5), 1,4- dihydroxy anthraquinone (DHA-1,4), resorcinol (R), hydroquinone (Hq), catechol (C), ethyleneglycol (EG), diethyleneglycol (DEG) and triethyleneglycol (TEG). All the polyesters were characterized by solubility, density, viscosity measurements, IR spectra and thermogravimetric analysis. All the polyesters are soluble at high temperature in acetone, dimethylformamide, dimethylsulphoxide, dimethylacetamide, etc. The polymer has reduced viscosity in the range 0.522- 0.739 dL g-1 in dimethylformamide at 30°C. Homopolyesters derived from phenolphthalein showed greater thermal stability than other polyesters.

Beech wood after drying and milling was reacted with alkylating and acetylating agents. Untreated beech wood meal was reacted with benzyl chloride in the presence of sodium hydroxide. Also beech wood meal in another experiment was pulped with ethylene glycol as pulping liquor for removing lignin and the delignified beech wood was reacted with benzyl chloride in the presence of NaOH. Untreated wood and delignified wood after benzylation show thermal flowability as determined by thermal mechanical analysis (TMA). The benzylation products of untreated and delignified wood were acetylated with acetic acid and acetic anhydride mixture. The thermal flowability of acetylation products were measured by TMA analysis. 1H NMR and FTIR spectra of products were also recorded.

Functionalization of polyethylene has been performed by means of homogeneous grafting reactions of maleic anhydride initiated by free radicals. Benzoyl peroxide, azobisisobutyronitrile, and dicumylperoxide have been used as free radical sources and their efficiency has been compared. The effects of the solvent, time and temperature of the reaction, and concentration of monomer on the percentage of grafting have been investigated. A comparison of the effectiveness of the nature of initiator, solvent, atmosphere and monomer concentration showed that polyethylene macroradicals are formed mainly through the chain transfer reactions. This mechanism of reaction was also confirmed by the influence of the nature of polymer and monomer concentration. Side groups of maleic anhydride and side chains of poly(maleic anhydride) are formed by addition of polyethylene macroradicals to the double bond of maleic anhydride molecule and by a combination of polyethylene macroradicals with those of poly(maleic anhydride).

Bisupported Ziegler-Natta catalyst of SiO2/MgCl2 (ethoxide type) /TiCl4 was prepared for polymerization of ethylene. SiO2 and Mg(OEt)2 were used as supports. Although MgCl2 known as best support for Ziegler-Natta catalyst, but due to high surface area and excellent morphological performance of SiO2, it was chosen as a support as well. Three catalysts of the above mentioned type were prepared using different ratios of Mg:Si and different methods of preparation of the catalyst. Triethylaluminum (TEA) was used as cocatalyst. The optimum molar ratio of Al:Ti=59.7:1 was obtained as the basis of polymer yield. Hydrogen gas was used as chain transfer agent. Increasing H2 concentration decreased the productivity of the catalyst. The effect of temperature between 40 to 70°C and the effect of monomer pressure of 1.5 to 7 bar on polymerization behaviour were studied, while the optimum ratio of Al:Ti and 25 mL/L H2 was used. Increasing temperature to 60°C increased the polymer yield obtained, but thehigher temperature, however, decreased the productivity of the catalyst. Increasing pressure of monomer sharply increases the productivity of the catalyst. Viscosity average molecular weight (Mv) for some polymers obtained were determined. Increasing Al concentration and H2 decreased Mv of polymer obtained.

Poly-β-hydroxybutyrate (PHB) is a biodegradable polymer which is regarded as a new environmentally compatible material. A wide variety of micro-organisms accumulate poly-β-hydroxybutyrate within cells as an intracellular storage material of carbon and energy. In this study, PHB was synthesized by Ralstonia eutropha (formerly Alcaligenes eutrophus) in a defined medium consisted of fructose as a sole carbon source. The effect of four process variables was studied to optimize the biosynthesis of PHB in bench scale. The results showed that the fresh inoculum at the mid-exponential phase lead to more growth during fermentation. The optimum shaking rate and temperature were 250 rpm and 25°C, respectively. The high concentration of fructose inhibited the growth, so it was optimized at 15 gL-1. Under these conditions, PHB was accumulated as inclusion bodies so that 70% of the dry cell weight of Ralstonia eutropha was composed of PHB. The yield coefficients of biomass and product were 0.3 and 0.21 g.g-1, respectively.

Three new poly Schiff bases were synthesized by polycondensation of diethylenetriamine, 1,2-diaminopropane and o-diaminobenzene with 5a,10b-dihydrobenzofuro [2,3-b] benzofuran-2,9- dicarbaldehyde II. The polymers have been characterized by their FTIR and 1H NMR spectra. The relationship of thermal stability of these polymers to their chemical structure was studied by thermogravimetric analysis (TGA) and differential Scanning calorimetry (DSC). Their average molecular weight was determined by GPC. These Schiff base polymers are soluble in common organic solvents. The poly Schiff base III copper complex was prepared and characterized by FTIR and UV/vis. The polymer chelate was insoluble in common organic solvents.

Acorona discharge treatment of low-density polyethylene film (LDPE) was carried out in preparation for flexographic printing. Such treatment of the PE film is necessary if maximum adhesion of ink is to be achieved. This project involved three different treating machines for which the current had to be manipulated in all the machines so that a standard treatment could be accomplished. Using a mathematical relation, current requirements for each machine were calculated and used to standardize treatment level of PE films. Standardization was achieved by controlling input current in all the three machines so as to attain a treatment level of 38 dynes/cm. This level of treatment showed the best results in adhesion of ink to the PE film during printing. The exercise also confirmed that printing must be carried out within 24 h of treatment since the level of treatment deteriorates with time.

Anew nonlinear axisymmetric finite element model has been developed for the stress-strain analysis of pneumatic tires. The model combines the built-in nonlinear capabilities of the commercial code COSMOS/M (NSTAR module) with tensorial calculations required to compute the stiffness properties of a cord-rubber composite in an arbitrary direction. This model is used for the analysis of a 175/70R14 steel-belted radial tyre under inflation loading. The results showed that ignoring the effect of bias cord angle (e.g., belt angle) on the elastic properties of the cord-rubber composite give rise to prediction of inaccurate tyre deformed shape. The accuracy and validity of the model has also been verified by the comparison of the value of the computed tyre crown displacement with available experimental results.

Telomerization of vinyl acetate(VAc) in chloroform and with 2,2’-azoisobutyronitrile (AIBN) initiator, was carried out to synthesize poly(vinyl acetate) (PVAc) with trichloromethyl (CCl3) end group which is called VAc telomer. The molecular structure and molecular weight distribution(MWD) of VAc telomers were characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). The effect of chloroform and AIBN on number average degree of polymerization (Dpn) and percent of telomerization were investigated. The kinetics of telomerization was studied and chain transfer constant of chloroform was determined. The synthesized PVAc with CCl3 end group (VAc telomer) was used as macroinitiator in atom transfer radical polymerization (ATRP) of methyl acrylate (MA) with CuCl/2,2''- bipyridine catalyst system to synthesize novel block copolymers of VAc and MA. Molecular structure and MWD of the PVAc-b-PMA copolymers were characterized by 1H NMR spectroscopy and GPC.