Search results for "Propylene"

CO2-Based Non-ionic Surfactants: Solvent-Free Synthesis of Poly(ethylene glycol)-block-Poly(propylene carbonate) Block Copolymers

2013

Copolymerization of carbon dioxide (CO2) and propylene oxide (PO) is employed to generate amphiphilic polycarbonate block copolymers with a hydrophilic poly(ethylene glycol) (PEG) block and a nonpolar poly(propylene carbonate) (PPC) block. A series of poly(propylene carbonate) (PPC) di- and triblock copolymers, PPC-b-PEG and PPC-b-PEG-b-PPC, respectively, with narrow molecular weight distributions (PDIs in the range of 1.05–1.12) and tailored molecular weights (1500–4500 g mol−1) is synthesized via an alternating CO2/propylene oxide copolymerization, using PEG or mPEG as an initiator. Critical micelle concentrations (CMCs) are determined, ranging from 3 to 30 mg L−1. Non-ionic poly(propylen…

Kompleksy metali przejściowych z zasadami Lewisa jako prekursory katalizatorów polimeryzacji olefin. Cz. I. Postęp w komputerowym modelowaniu procesu…

2001

A review with 35 references covering molecular modeling in coordination polymerization over homogeneous and heterogeneous Ziegler-Natta catalysts. The study includes supports, cocatalysts, Lewis bases and solvents. Recent progress in elucidating the mechanisrn of elementary polymerization steps is presented against the background of rapidly deveIoping computational methods and available computational power. Theoretical studies on polymerization mcchanisms and structure of active centers are described (egns. 1-4). Authors own calculations are used to compare [MtC14(THF)2] complex-based (Mt = Ti, Hf or Zr) heterogeneous catalysts. The geometrical characteristics of precursors is presented (Ta…

2015

One-pot combination of the in-situ generation of hydrogen peroxide (H2O2) with selective oxidation reactions enhances the environmental and economic attractiveness of the use of H2O2 as green oxidant at industrial scale. This tandem reaction improves not only the safety aspects associated to H2O2 storage and transportation but also reduces the capital and operation costs. This review covers the progress in the field focussing on the areas of catalysis development, mechanistic understanding and engineering approaches (such as membrane reactors) for specific systems involving epoxidation of propylene oxide, hydroxylation of benzene, oxygenate synthesis from methane and Fenton processes, highl…

Nature of activating effect of two-step polymerization of propylene

1999

The prepolymerization effect on propylene polymerization in the presence of a TiCl 3 -based catalyst, modified by di-n-buthyl ether, was studied. The influence of prepolymerization on the electron spin resonance spectra and morphology of the catalyst, as well as the properties and the morphology of both prepolymer and regular polymerization products, was investigated. The polymer morphology was evaluated through scanning electron microscopy, polymer bulk density, and particle size distribution. Some evidence of the enhancement effect of prepolymerization on the catalyst activity and stereospecificity was obtained. No influence from prepolymerization was observed on molecular weight and its …

Kompleksy metali przejściowych z zasadami Lewisa jako prekursory katalizatorów polimeryzacji olefin. Cz. II. Postęp w komputerowym projektowaniu kata…

2001

Dokonano przeglądu prac dotyczących komputerowego projektowania katalizatorów do polimeryzacji olefin z punktu widzenia wpływu katalizatorów na przebieg tego procesu. Omówiono osiągnięcia w teoretycznym przewidywaniu katalitycznych właściwości kompleksów metali przejściowych, które dokonały się dzięki zrozumieniu mechanizmu polimeryzacji, charakteru centrów aktywnych, przyczyn aktywności takich katalizatorów oraz roli poszczególnych ich składników. Przedstawiono również zagadnienia, na których prawdopodobnie skupią się obecne i przyszłe prace teoretyczne w dziedzinie polimeryzacji koordynacyjnej (rola kokatalizatorów i zasad Lewisa dodawanych do układów katalitycznych, wpływ warunków doświa…

LAPAROSCOPIC SACROCOLPOPEXY IN THE TREATMENT OF VAGINAL VAULT PROLAPSE AND RECTOCELE. RETROSPECTIVE STUDY OF 64 CASES

2003

Objectives: To evaluate the results of the laparoscopic sacrocolpopexy using a polypropylene mesh. Methods: We performed laparoscopic sacrocolpopexy on 64 pts who presented a prolapse of the vaginal vault between the II and the IV degree according to HWS classification. The mean age was 65 (range 58-76) with variable parity. The vaginal vault prolapse was present after abdominal hysterectomy in 33 pts.(51%) and after vaginal hysterectomy in 24 pts. (38%). 7 pts. (11%) were affected by an isterocele of III -IV . 8pts(12%) presented a vault prolapse of I degree, 16pts.(25%) of II degree, 15pts.(23%) of III degree, 18 pts.(%) of VI degree.They were also affected by different degrees of cystour…

Механика композитных материалов, 2022, Т. 58, No 1, Январь-февраль

2022

Acute inflammatory response after inguinal and incisional hernia repair with implantation of polypropylene mesh of different size.

2005

The purpose of this study was to assess the modifications of interleukin (IL)-6, C-reactive protein (CRP), leukocytes and fibrinogen after implantation of polypropylene mesh.Thirty-six patients were included in this study and divided into two groups. To the first group were allocated patients affected by inguinal hernia and undergoing conventional repair (subgroup Ia) or hernioplasty with 40-cm(2) polypropylene mesh (subgroup Ib). To the second group were allocated patients affected by incisional hernia and undergoing conventional repair (subgroup IIa) or incisional hernia repair with 400-cm(2) polypropylene mesh (subgroup IIb). Peripheral venous blood samples were collected 24 h before sur…

Effect of propylene glycol on pre- and post-partum performance by dairy ewes

2005

This study was carried out in order to determine the effects, after feeding propylene glycol to Valle del Belice ewes 30 days prepartum and 30 days postpartum, on metabolic profiles, body-condition score, milk yield, milk composition, milk clotting ability and the performance of suckling lambs. Ewes were blocked by parity, body-condition score and previous milk production, and assigned randomly to either a control diet or a diet containing propylene glycol fed at the rate of 80 g/ewe/day (low PG) or 160 g/ewe/day (high PG). Feeding propylene glycol prepartum decreased the concentration of BHBA and NEFA and increased the concentration of glucose in the ewes’ plasma. Milk yield from ewes fed …

Biomechanical and histological evaluation of abdominal wall compliance with intraperitoneal onlay mesh implants in rabbits: A comparison of six diffe…

2012

Abstract Background An ideal prosthetic mesh for incisional hernia repair should mimic the anisotropic compliance of the abdominal wall, and at lower loads should exhibit higher distensibility without impairment of safety at higher loads. This study evaluated the biomechanical properties of six meshes in a rabbit model. Methods New Zealand white rabbits were used for this study. Two meshes of the same brand (Ethicon Physiomesh™, Bard Composix ® L/P, Gore Dualmesh ® , Bard Sepramesh ® , Ethicon Proceed ® or Parietex™ Composite) were implanted into each animal for assessment of intra-abdominal hernia repair, with a total of ten meshes per group. Twelve weeks after implantation, the abdominal …