Production of Long‐Chain Branched Polyolefins with Two Single‐Site Catalysts: Comparing CSTR and Semi‐Batch Performance

We developed a mathematical model to describe the solution polymerization of olefins with two single‐site catalysts in a series of two CSTRs. The model was used to simulate processes where semi‐crystalline macromonomers produced in the first reactor are incorporated as long chain branches onto amorphous (or lower crystallinity) chains in the second reactor (cross‐products). The simulation results show that CSTRs are more efficient to make chains with high LCB density and high weight percent of cross‐products. The model can also predict the polydispersity index, average chain lengths, and fractions of the different polymer populations, and help the polymer reactor engineer formulate new products with complex microstructures.

     

Simulation of Polymerization and Long Chain Branch Formation in a Semi‐Batch Reactor Using Two Single‐Site Catalysts

We developed a mathematical model for the solution polymerization of olefins in a semi‐batch reactor with two single‐site catalysts. In the propylene polymerization case, our objective is to study the production of a thermoplastic elastomer using two catalysts, one capable of forming isotactic chains containing terminal vinyl bonds (macromonomers) and the other producing atactic chains while also being able to copolymerize macromonomers to form long chain branches. A similar thermoplastic elastomer can be produced by polymerizing ethylene and α‐olefin comonomers when the α‐olefin reactivity ratios of the two catalysts are significantly different.

     

Study of complexation of phenylaza-15-crwon-5, 4-nitrobenzo- 15-crown-5, and benzo-15-crown-5 with Ag+, Tl+ and Pb2+ ions in methanol by competitive potentiometry

The complexation reaction of phenylaza-15-crwon-5, 4- nitrobenzo- 15-crown-5, and benzo-15-crown-5 with Ag⁺, Tl⁺ and Pb²⁺ ions in methanol solution have been studied by a competitive potentiometric method. The Ag⁺/Ag electrode used both as an indicator and reference electrode in a concentration cell. The emf of cell monitored as the crown ethers concentration varies through the titration. The stoichiometry and stability constants of resulting complexes have been evaluated by MINIQUAD. The stoichiometry for all resulting complexes was 1:1. The stability of these metal ions with derivatives of 15-crown-5 are in order phenylaza-15-crown-5 > Benzo-15-crown-5 > 4-nitrobenzo-15-crown-5, and for the each used crown ethers are as Pb²⁺ > Ag⁺ > Tl⁺. The effect of the substituted group on the stability of resulting complexes was considered. The obtained results are novel and interesting.     

On some low separation axioms via λ-open and λ-closure operator

In this paper, we introduce and study two new low separation axioms called λ-R ₀ and λ-R ₁ by using the notions of λ-open sets and λ-closure operator.     

New olefin block copolymers of ethylene/1-hexene synthesized by iron and zirconocene catalysts in the presence of ZnEt2

Journal of Thermal Analysis and Calorimetry - Development of olefin block copolymers (OBCs) based on new catalytic systems is challenging. We evaluate the performance of rac-ethylenebis(1-η...     

Polymerization of ethylene using a series of binuclear and a mononuclear Ni (II)‐based catalysts

A novel series of homo‐, bi‐, and mononuclear Ni(II)‐based catalysts (BNC_n n = 1–4, MNC₄) were used for ethylene polymerization. The optimum conditions for the catalyst BNC₄ (the highest catalytic activity) was obtained at [Al]/[Ni]=2000/1, T_p = 42 °C, and t_p = 20 min that was 1073 g PE/mmol Ni h. In theoretical study, steric and electronic effects of substituents and diimine backbone led to prominent influence on the catalyst behavior. The highest M_V was resulted from polymerization using BNC₄; however, the highest unsaturation content was obtained from BNC₁. GPC analysis showed a broad MWD (PDI = 17.8). BNC₁ and BNC₂ in similar structures showed broad peaks in DSC thermogram, while BNC₃ and BNC₄ with more electronic effects showed a peak along with a wide shoulder. Monomer pressure increasing showed enhancing in activity of the BNC₄, meanwhile a peak with shoulder to a single peak in DSC thermogram and uniformity in morphology of the resulted polymer were observed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3000–3011     

Some results in BL ‐algebras

We define the set of double complemented elements in BL‐algebras and state and prove some theorems which determines properties of these sets. We introduce the notion of an almost top element and study the properties of these elements (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of pulse duration on KrF laser treatment of a polyethersulfone film: cell culture study

KrF laser processing of polyethersulfone (PES) films at three different pulse durations regarding to the change in biocompatibility is presented with cell culture study. Various microstructure and chemistry results were obtained on the surface upon laser irradiation. It is shown that nanoscale hydrophilic ripples significantly affect the adhesion of L929 cells on the surface.