Search results for "RIZ"

Synthesis and catalytic properties for olefin polymerization of new vanadium complexes containing silsesquioxane ligands with different denticity

2017

A series of new vanadium-silsesquioxanes (2a − 2d) was prepared by reacting VCl4 with not fully condensed silsesquioxanes (having from one to four silanol groups) and evaluated as pre-catalysts in olefin polymerization. The activation of 2a − 2d with EtAlCl2 generated highly active catalysts for ethylene polymerization, yielding high molar mass polymers with narrow dispersity. Ultra-high molar mass polyethylenes, Mw up to 4 × 106 g mol−1, were obtained with methylaluminoxane and Al(iBu)3/[Ph3C][B(C6F5)4] as activators. Upon treatment with methylaluminoxane and boron compounds, all vanadium pre-catalysts were active in 1-octene polymerization as well, and produced isotactic-rich poly(1-octen…

Recycling ground tire rubber (GTR) scraps as high-impact filler of in-situ produced polyketone matrix

2014

Block copolymers from ionic liquids for the preparation of thin carbonaceous shells

2017

This paper describes the controlled radical polymerization of an ionic-liquid monomer by RAFT polymerization. This allows the control over the molecular weight of ionic liquid blocks in the range of 8000 and 22000 and of the block-copolymer synthesis. In this work we focus on block copolymers with an anchor block. They can be used to control the formation of TiO2 nanoparticles, which are functionalized thereafter with a block of ionic-liquid polymer. Pyrolysis of these polymer functionalized inorganic nanoparticles leads to TiO2 nanoparticles coated with a thin carbonaceous shell. Such materials may, e.g., be interesting as battery materials.

Effect of hydrogen on the ethylene polymerization process over Ziegler–Natta catalysts supported on MgCl2(THF)2. II. Kinetic studies

2001

This article reports on a study of the effects of hydrogen on the activity of vanadium and titanium catalysts supported on MgCl2(THF)2 in ethylene polymerization. It was found that hydrogen did not change the stable nature of the active sites and the polydispersity index of the polyethylene obtained. The propagation rate, expressed as kp, was found to be independent of the presence and concentration of hydrogen, indicating that this reacting agent does not modify the reactivity of the active sites. However, the presence of hydrogen in the polymerization medium is responsible for partial deactivation of the active sites just before polymerization is initiated.

Organometallic VCl4-based catalyst supported on MgCl2(THF)2 for ethylene polymerization

1997

A Ziegler-Natta catalyst was obtained by milling VCl4 with the magnesium support in the from of the MgCl2(THF)2 complex, followed by activation with an organoaluminum compound. This catalyst was employed in low-pressure polymerization of ethylene. The system was found to offer a very high activity and to polymerize ethylene at a rate of a few hundred kg PE/(g Vh) with the resulting molecular weight of the product very high. The kinetic investgation of the polymerization process revealed over 80 % of the transition metal atoms to be involved in the forming catalytic active sites, undergoing virtually no deactivation over the period of time studied.

Weryfikacja kinetycznego modelu polimeryzacji etylenu wobec metaloorganicznych katalizatorów wanadowych na nośniku magnezowym

1998

The kinetic studies are reviewed on low-pressure polymerization of ethylene over two types of organovanadium catalysts, viz., MgCl 2(THF) 2/VCl 4/Et 2AlCl and MgCl 2(THF) 2VOCl 3Et 2AlCl, each deposited on a magnesium carrier. The polymerization rate was found to be directly related to the catalyst and monomer concentrations (Figs. 2 and 3), unless when the access of the monomer to the reactive V-C bond is restricted by diffusion. Polymer chain termination step was found to result from the reaction of the transfer onto the monomer and to be associated with the regeneration of the active site on which a new macromolecule can be formed. A kinetic model was developed for the ethylene polymeriz…

Synthesis of oxide-supported vanadium catalysts and their activity in ethylene polymerization

1999

The activity of oxide-supported vanadium-based catalyst systems (VOCl 3/Et 2AlCl) in low-pressure ethylene polymerization and the properties of the resulting polyethylenes were studied in relation to the type and mode of modification of the oxide support. Alumina, silica and an un"conventional silica-type material prepared by the sol-gel process were used as supports. Results are compared with those obtained earlier with a catalyst supported on MgCl 2(THF) 2. Of the oxides studied, the silica-type sol-gel material dehydrated and subsequently modified with Et 2AlCl proved to be the best carrier for a vanadium catalyst. The polyethylene prepared by using this catalyst support was found to exh…

FRESH AND DEHYDRATED SULLA FORAGE IN DAIRY EWES FEEDING: EFFECTS ON FEED UTILIZATION, OXIDATIVE STATUS AND PROPERTIES OF MILK AND CHEESE

2022

Prickly pear pulp in the feeding of livestock ruminants: preliminary investigation

2019

In Sicily, the current increasing cultivation of Opuntia ficus-indica (L.) Mill. corresponds to a availability of prickly pears pulp (PPP) that residues from fruits processing for juice extraction, comprised of peel, pulp and seeds. This investigation aim to evaluate the nutritional traits of PPP for ruminants feeding, and the effect of potassium metabisulfite (PMB) as a natural stabilizer to limit initial rapid PPP fermentation. The by-product, collected in August, included 28% of peel and pulp (PP) and 72% of seeds on dry matter (DM), with seeds higher in ether extract (EE) and NDF and comparable for DM and crude protein (CP) (DM 35.5, 35.9 and 35.6%; EE 6.5, 3.6 and 8.5% DM; CP 6.5, 6.0 …

Polysarcosine-Based Lipids: From Lipopolypeptoid Micelles to Stealth-Like Lipids in Langmuir Blodgett Monolayers.

2016

Amphiphiles and, in particular, PEGylated lipids or alkyl ethers represent an important class of non-ionic surfactants and have become key ingredients for long-circulating (“stealth”) liposomes. While poly-(ethylene glycol) (PEG) can be considered the gold standard for stealth-like materials, it is known to be neither a bio-based nor biodegradable material. In contrast to PEG, polysarcosine (PSar) is based on the endogenous amino acid sarcosine (N-methylated glycine), but has also demonstrated stealth-like properties in vitro, as well as in vivo. In this respect, we report on the synthesis and characterization of polysarcosine based lipids with C14 and C18 hydrocarbon chains and their end g…