Process Conditions in Preparation of MgCl2 Adduct on Crystalline Structure of the Support in ZN Catalyst

MgCl2/C2H5OH adducts with constant relative ratio of 1/3 were prepared and kept at 120oC for different lengths of times of 5, 10, 20, 30, 50, 90,120 and 220 h. Then the samples were quenched and analyzed by XRD and BET. No meaningful changes were observed in the specific surface area of the samples, while XRD spectra showed 3 peaks at 2θ<15o for samples kept at 120oC for 5 h. These 3 peaks were gradually replaced by a single peak for samples kept at120 oC for 120 h and beyond. Dealcoholation of the samples caused a dramatic change in specific surface area from 3.6 m2/g to 284.7 m2/g. Also XRD indicated that the peak at 2θ <15o totally vanished and it was replaced by a weak amorphous type of peak. Catalysts produced from these supports were used to polymerize ethylene. It was observed that with increasing the specific surface area of the supports and the time of polymerization, the activity of the catalysts was enhanced dramatically

Crystallization Behavior of Poly(l-lactide) Films in Presence of Mg(OH)2 and l-Lactide

The effects of magnesium hydroxide and l-lactide dimer as additives on thermal properties and morphology of poly(l-lactide) (PLLA) films were studied. Hence, neat PLLA films and films containing additives (10% w/w) were prepared in dichloromethane at room temperature via solution casting. To evaluate thermal history on polymer properties, PLLA films were annealed by different processes. In one process, designated as A, PLLA films were heated from 20 up 140oC, then held for 1 h and cooled to room temperature. In another process, designated as B, melted PLLA sampleswhich had been maintained at 200oC for 5 min were cooled with a rate of -20oC/min to 140oC and annealed for 1 h before being cooled to room temperature. In the next process designated as C, the melted PLLA samples after5 min of staying at 200oC were being quenched to 0oC. Then the samples were heated to 140oC followed by annealing for 1 h before being cooled to room temperature. The crystallization and morphology properties of PLLAfilms were studied using polarized optical microscopy and differential scanning calorimetry. It is found that the percentage of crystal and spherulitic formation inside PLLA films were influenced by thermal history and presenceof the additives. The type of additives did not affect melting point (Tm) of the films annealed through different processes of A to C, while they had influence on Tm of the films, significantly. It is to be noted that some spheruliteswere formed in films during B process. During C process, however, the nucleation rate increased due to quenching which enhanced the spherulites formation

Synthesis of (Ind)2ZrCl2 Catalyst for Copolymerization of Ethylene and Propylene: Parameters Effect on Productivity

Bis(indenyl)zirconium dichloride as a catalyst was synthesized using a modified method at the room temperature. Polymerization of ethylene and copolymerization of ethylene and propylene were carried out by this metallocene catalyst. Ethylene propylene (P/E) feed ratios of 0.25, 0.5, 1, and 2 were employed into the copolymerization systems. Copolymerization conditions like cocatalyst/catalyst ratio, copolymerization temperature, feed ratio and the viscosity average molecular weight (Mv) changing with copolymerization temperature were investigated. Higher ratio of [Al]/[Zr]=750:1 increased the activity of the catalyst. However, higher concentration of the cocatalyst slightly reduced the activity. Viscosity-average molecular weight of polymer decreased with high ratio of [Al]/[Zr]. The highest activity was obtained at 60oC. Increases in copolymerization temperature decreased the viscosity-average molecular weight and ethylene content of the polymeric products. Increases in propylene content of the feed ratio producedamorphous polymers with products of increased glass transition temperatures.Kinetic reaction displayed a decay type of reaction

Preparation of Silicious Mesoporous Spherical and Rod- Like MCM-41 Using Cetyltrimethylammonium Bromide as the Structure Directing Agent

MCM-41 is one of the groups of mesoporous materials that have wide applications as adsorbents, ion exchangers and catalyst supports. In this work spherical and rod-like MCM-41s were synthesized in homogeneous and heterogeneous reaction media, respectively. For synthesis of these materials the cationic surfactant cetyltrimethylammonium bromide (CTMABr) was used as template and tetraethylorthosilicate (TEOS) was used as the silica source. The polymerization process of the silica source was performed in basic and acidic media using ammonia or HCl as catalysts. BET (Brunauer-Emmett-Teller), FTIR, X-Ray diffraction and scanning electron microscopy analysis confirmed the structures of these synthesized materials. Finally a mechanism was proposed for the formation of these structures