saeed ahmadjo

Demand for the use of polymers in different industries with different properties is increasing. However, pure polymer does not have the ability to create a wide range of desired features. To solve this problem, various additives are used, many of which are minerals. The polar nature of these additives has made them impossible to use in non-polar polymers, such as polyolefins, due to the incompatibility and poor interface adhesion. Various methods are used to increase compatibility, one of which is the use of compatibilizers. Functionalized waxes are among the materials that researchers have studied over the years. The backbone of functional waxes is miscible with a polymer, and the functional groups on the wax surface can interact with the groups present on the additive surface. Therefore, their use improves the dispersion and distribution of additive particles in the polymer. Also, due to their low molecular weight, these waxes can penetrate the pores and capillaries on the additive surface and act as a successful co-compatibilizer. In this study, first, the methods of increasing compatibility and the cases used for this purpose are briefly reviewed. Then, the performance of functionalized waxes as a compatibilizer and co-compatibilizer and their effect on the physical, mechanical, and thermal properties of the polymer composites are investigated in details.

Epoxy resin has remarkable properties including excellent mechanical and electrical properties, thermal and chemical stability, and resistance to creep. On the other side, these resins are brittle with low resistance toward crack initiation and its growth. In order to solve this problem, thermoplastic polysulfone and graphene nanosheets have been used as filler for improving the flexibility of epoxy coatings. The effect of adding different amounts (1, 0.5, 2.5, 5 wt%) of polysulfone and 0.5 wt% of graphene nanosheets on the epoxy properties was investigated by thermal analysis (DSC), tensile strength, impact resistance and determining the gel content of samples. The results showed that the tensile strength of epoxy resin increased by adding polysulfone, and the graphene nanosheets could improve flexibility of the sample containing 1 wt% polysulfone. The study of thermal properties of cured samples by means of DSC analysis showed that the addition of polysulfone into the epoxy network resulted in changing the glass transition (Tg) of the resin. With incorporation of graphene nanosheets into the polymer matrix, the modulus decreased due to the reduction in number of crosslinks. The study in impact resistance of the samples showed that those containing 1 wt% polysulfone and 0.5 wt% graphene displayed high strength and impact resistance. These types of compounds can be used in flexible and anticorrosion coatings.

Slurry copolymerization of ethylene and propylene (EPM) was carried out in dry nheptane using high activity catalyst system of SiO2/MgCl2/TiCl4/EB/TiBA (or TEA)/MPT/H2. The structure of four EPM samples with ethylene content of 30%, 40%, 50% and 80% were analyzed using 13C NMR method. The complex spectra taking at high field are interpreted as resulting from ethylene propylene sequence placements. A methylene sequence distribution from one to six is given for four different ethylene propylene copolymer samples distribution. Increasing ethylene content of the copolymer increased EEE triad and decreased PPP triad distributions. Due to higher activity of ethylene monomer increasing its content from 30% to 80% the EEE triad distribution increased from 4.5% to about 73%. In the sample containing 30% of ethylene the PPP triad was less than 30% which is an indication of very high relative activity of ethylene to propylene for copolymerization using the catalyst system. The catalyst system used was quite active for the copolymerization and may introduce alternative sequence distribution in the polymer chain. Higher portion of propylene in the copolymer significantly increased the sequence of single methylene units and decreased six and more consecutive units. The EPM copolymer containing 30% to 50% ethylene have amorphous properties.

Bis(cyclopentadienyl) zirconium dichloride (Cp2ZrCl2) as a homogeneous metallocene catalyst was manufactured in laboratory scale under highly controlled conditions. Ethylene polymerization was carried out using this catalyst while, methylaluminoxane (MAO) was used as a cocatalyst. Activity of 5759 gPE/mmol Zr.h at [Al]/[Zr] molar ratio of 770/1 was obtained. Polymer yield was increased with increasing in [Al]/[Zr] ratio to a limiting value. Addition of hydrogen as a chain transfer agent up to 120 cm3/L solvent, increased the activity of the catalyst. Polymerization was carried out at monomer pressure of 1 to 5 atm, and temperature of 40oC to 80oC. Polymerization activity was increased with increasing temperature to 60oC and slightly decreased with more increase in temperature. Upon the addition of catalyst a sudden increase of 10oC in temperature was observed, particularly when polymerization temperature was higher than 50oC. This increase could be due to high rate of polymerization which at high temperature could affect catalyst activity. Monomer pressure up to 2 atm increased productivity of catalyst. Increase in [Al]/[Zr] ratio, polymerization temperature and H2 concentration decreased Mvof polymer obtained. Melting point of polymer also decreased with increasing [Al]/[Zr]ratio. Density of obtained polyethylene was 0.940-0.950 g/cm3. Tg of one of the polymer samples was determined which was 99.9oC.

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.