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Showing 1 to 20 of 25 for “"Chain branching"”.
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Flow Behavior of Sparsely Branched Metallocene-Catalyzed Polyethylenes
… understanding of the influences that sparse long-chain branching has on the rheological and processing behavior of commercial metallocene polyethylene (mPE) resins. In order to clarify these influences, a series of six commercial polyethylenes was investigated. Four of these resins are mPE resins …
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Incorporation of Polar Comonomers Into High Density Polyethylene With a Cyclopentadienyl-Amido Titanium Catalyst
… by 1 was substantially linear HDPE with long chain branching and that comonomer incorporation reduced the Tc and Tm, probably due to increased short chain branching. 1-TMSO-9-Decene was the most effective comonomer, as it had the highest incorporation rates (8.0 mol%) of all three of the polar …
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The Formation, Propagation and Stability of Self-Sustained Detonation Waves in Gaseous Mixtures, Condensed-Phase Explosives and Media With Hydraulic Resistance
… the detonation, wherease an increase of the chain-branching temperature has the opposite effect.
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Influence of Polyolefin Contamination on the Thermal Characteristics of Bottle Grade Recycled Polyethylene Terephthalate
… of cooling rates and that cross-linking and chain branching predominated over chain scissions as a result of repetitive extrusions. The crystallisation process of the non contaminated rPET-bg and rPET-bg contaminated with polyolefin depended on many influencing factors, such as impurities, …
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UNDERSTANDING THE MOLECULAR WEIGHT DISTRIBUTION SHAPE-PROPERTY RELATIONSHIP BASED ON LINEAR UNIMODAL AND BIMODAL POLYETHYLENES MODEL SYSTEM
… MWD shape without controlling dispersity, chain branching, phase separation or average molecular weight make it hard to decouple the independent contribution of MWD shape. In this work, we have successfully synthesized unimodal and bimodal polyethylenes with low branching, good miscibility, …
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Thermochemistry and kinetics: hydrogen atom addition reactions with alkenes, oxidation of cyclopentadienone, trifluoroethene and transport properties
… kinetic parameters and to show significance of chain branching as a function of temperature and pressure. The cyclopentadienone vinylic carbon radicals of with molecular oxygen appear to undergo chain branching via reaction with O_2, to a higher extent to that of vinyl and phenyl radicals. …
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Linking Rheological and Processing Behavior to Molecular Structure in Sparsely-Branched Polyethylenes Using Constitutive Relationships
… resins, with varying degrees of sparse long chain branching (LCB) content, is used to study the effect of both LCB content and distribution on the rheological and commercial processing response using the Pom-pom constitutive relationship. A flow instability known as ductile failure in …
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A study of thermal decompositions of an allylic hydroperoxide /|nby Thomas A. McCarrick. -- 260 St. Catharines [Ont.] : Dept. of Chemistry, Brock University,
… of the kinetic ch a in length indicated a chain length of about fifty. A degenerat i ve chain branching mechanism 1s proposed which predicts the multi t ude of products which Rre observed e xperimentally as well as giving activation energies and log A factors si~il a r to those found …
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Thermorheology and processing of polyethylene blends : macromolecular structure effects
… was studied with emphasis on the effects of long chain branching. First, a linear low-density polyethylene (LL3001.32) was blended with four LDPE's having distinctly different molecular weights. At high LDPE weight fractions, DSC melting thermograms have shown three different polymer phases; two …
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A study of the thermal decomposition of allyl t-butyl peroxide and 3-hydroperoxy-1-propene (allyl hydroperoxide) in toluene /|nby Krishnankutty Nair V. G. -- 260 St. Catharines [Ont. : s. n.],
… of 10.6. Enormous production of radicals through chain branching may explain these relatively low values of E and log A. The complexity of the reaction is indicated a by the formation of various products of the decomposition. A study of the radical attack of the hydro peroxide at lower …
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Developing fundamentally based models for autoignition
… These reactions are competitive with the main chain branching pathway, so their rate constants affect the ignition timing of the system. There are no direct measurement experimental results available for these reactions. We used quantum chemistry, mainly the complete-basis-set extrapolation …
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Dilute solution studies of molecular weight distributions of nitrocellulose, modified lignins and PMMA graft polymers
… weights but containing different levels of branching. Variable temperature GPC/LALLS/DV was employed to obtain molecular weight distributions, branching parameters, average chain dimensions and information on the hydrodynamic behavior of these branched systems. Samples containing up to 40% …
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A Study of Plasma Ignition Enhancement for Aeroramp Injectors in Supersonic Combustion Applications
… a radical known to participate in important chain-branching combustion reactions. Based on the knowledge gained, and encouraging results, a candidate scramjet igniter and flameholder was designed. The design was observed to exhibit a synergistic effect between the plasma igniter and fuel …
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Synthesis of well-defined single and multiphase polymers using various living polymerization methods
… utilized as model homopolymers exhibiting long chain branching. The methacryloyloxy functionalized PDMS macromonomers were free radically and anionically copolymerized with MMA to yield PMMA-g-PDMS copolymers. The graft copolymers were fractionated and their chemical composition distributions …
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Reactive modification and crystallization behavior of foamed poly(butylene terephthalate)
… on the PBT/modifier reaction kinetics. Chain branching was then carried out by single screw extrusion, where the competing degradative chain scission reaction needed to be taken into account. Applications of fundamentals of extrusion theory to the reactive extrusion process enabled the …
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Novel Monomer Design for Next-Generation Step-Growth Polymers
… poor mechanical properties. Introduction of long-chain branching (LCB) into PEIs provided a unique comparison between a commercially relevant PEI (Ultem® 1000) and a regioisomer infrequently found in the literature. Thermal stability remained consistent for each regioisomer, and Tgs for the 3,3'- …
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Determination of the Composition and Architecture of the Mitochondrial Ubiquitome in PINK1/Parkin Mitophagy
… has been done to establish the substrates and chain type composition of the Ub placed on mitochondrial substrates by Parkin, little work has been done to establish the broader Ub chain architecture: the degree of chain branching, and the relationship between phosphorylation and chain formation …
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Autoignition and combustion chemistry of kerosene type fuels and components
… that reactivity is controlled by low-temperature chain branching: R + O2 ↔ RO2 ↔ QOOH (+O2) ↔ OOQOOH → 2OH + products. The variation and/or similarities in ignition behavior observed amongst fuels is attributed to their different concentrations of fuel components, whose fractions control the …
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Einfluss der Topologie auf die rheologischen Eigenschaften von Polymeren
Ziel der Arbeit war es, den Einfluss der molekularen Architektur – der sogenannten Molekültopologie – von Polymeren auf deren viskoelastische Eigenschaften zu untersuchen, um ein Verfahren zur Charakterisierung der Langkettenverzweigungen (LKV) abzuleiten.
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Oxidation and stabilisation chemistry of metallocene-based polyolefins during melt processing
… can be synthesized with exactly controlled short chain branches and stereo-regular microstructure. The unique properties of these polymers have led to their applications in many areas. As a result, it is important to have a good understanding of the oxidation mechanism of m-LLDPE during melt …
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