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Showing 1 to 20 of 102 for “"molecular weight distribution"”.
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Additive Manufacturing of Commercial Polypropylene Grades of Similar Molecular Weight and Molecular Weight Distribution
… properties of commercial PP grades, of similar molecular weight (MW) and molecular weight distribution (MWD), on printability is still to be investigated. Those commercial PP grades can have wide variation in properties such as Melt Flow Index (MFI), additive content, and polymer architecture …
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A study of the relation between molecular weight distribution and mechanical properties of polyvinyl alcohol
… the relation between mechanical properties and molecular weight distribution of polyvinyl alcohol was carried out. The polyvinyl alcohol was fractionated with respect to degree of polymerization (D.P.) by precipitation of the fractions from 2% solution in water with a n-propyl alcohol-water …
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UNDERSTANDING THE MOLECULAR WEIGHT DISTRIBUTION SHAPE-PROPERTY RELATIONSHIP BASED ON LINEAR UNIMODAL AND BIMODAL POLYETHYLENES MODEL SYSTEM
Molecular weight distribution (MWD) shape is crucial in determining the properties of polymers. Previous studies on comparison of the unimodal and bimodal MWD shape without controlling dispersity, chain branching, phase separation or average molecular weight make it hard to decouple the independent …
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Dynamics of Flow-Induced Structure Formation in Drag Reducing Polymer Solutions
Work on the effects of strong shear on the molecular weight stability finds small degradation in the polymers' average molecular weight and molecular weight distribution. Experiments with HPAM and PAM solutions in a large channel flow loop at Re ≥ 20,000 provide evidence of the importance of …
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Block copolymer characterization by gel permeation chromatography
… to propose a method to determine the composition distribution, on one hand, and the molecular weight distribution, on the other hand, for block copolymers. The technique selected to determine this kind of information was Gel Permeation Chromatography, because, since its introduction in 1964, it …
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A Systems Approach to the Modeling and Control of Molecular, Microparticle, and Biological Distributions
… in which the output variable takes the form of a distribution: molecular, microparticle, and biological distributions. This approach involves incorporation of sensor technology and experiments, model identification, simulation algorithm development, parameter sensitivity analysis, parameter …
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The cationic ring-opening polymerization of cyclic ethers
… chromatography studies showed that the molecular weight distribution of the samples of polyoxetanes were bimodal. This was in accordance with previous work establishing that the cyclic tetramer is found in much higher proportions than any of the other cyclic oligomers. However the …
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A study of the overall internal dynamic mode of poly(ethylene oxide) in methanol with and without lithium perchlorate
… of the overall internal relaxation mode of high molecular weight, narrow molecular weight distribution PEO in methanol with and without the presence of LiClO 4 is so difficult as to be impractical. Moreover, PCS analysis proved to be extremely sensitive to small differences in data quality which …
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Study of Neem bark tannins for the leather industry
… checked by HPLC on Lichrosorb RP8 column. The molecular weight distribution ranges between 250 and 5500 and the average molecular weight distribution was found to be 1550 by gel permeation chromatography. Gas chromatography-mass spectroscopy demonstrated the complex nature of NBT molecular …
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Synthesis, characterization and kinetic investigations of heterophase materials prepared using group transfer polymerization
… temperature range. The degree of control over molecular weight and molecular weight distribution rivals that afforded through living anionic techniques for the preparation of poly(alkyl methacrylate)s. The objectives of this research were many fold. The first was to establish GTP as a routine …
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The sol-gel polymerization of octamethoxysilsesquioxane
… sol-gel system suggested that an extremely broad molecular weight distribution of silicate polymers was produced. These findings were consistent with predictions based on a covalent network theory of silica gelation (Flory-Stockmayer) theory.
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Synthesis and Characterization of Tailored Photoactive Macromolecules
… and gain the ability to reversibly control molecular weight and crosslink density using UV light. The cinnamates and coumarins were reacted onto the polymers via multiple reaction pathways. Polymers were functionalized with coumarin or cinnamate groups via an esterification reaction between …
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Computational Studies of Polyetherimides: Beyond All-Atom Molecular Dynamics Simulations
… properties, and chemical stability. All-atom molecular dynamics (MD) simulation is a useful tool to study polymers, but the accessible length and time scales are limited. In this thesis, we explore several computational methods that go beyond all-atom MD simulations to investigate …
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Polymer structure and property studies in elongational rheology, spherulite deformation, and biaxial strain induced crystallization
… of molten polyethylene was sensitive to both molecular weight distribution and shear modification. The effects of molecular weight distribution and shear modification were rationalized from a molecular point of view. A model is proposed which is based on the concept of a molecular network and …
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Studies in the anionic polymerization of methyl methacrylate
… of the solvent. Trends were assessed in terms of molecular weight, molecular weight distribution and tacticity. In addition, a second monomer addition test was carried out to verify that the polymerization was truly a living one, and a kinetic study was attempted. Studies to investigate the effect …
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Structure-property relationships in novel ionomers
… primary and secondary SAXS peaks when the molecular weight distribution is narrow (Mw/Mn ca. 1.15). These SAXS peaks are interpreted as due to non-global lamellar or cylindrical ionic domain order. The non-global ordering strongly affects the tensile and dynamic mechanical properties of the …
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Structure-property behavior of free radical synthesized polydimethylsiloxane-polystyrene block polymers and polytetramethyleneoxide based ionene elastomers
… radical synthesized PDMS-PS block polymers, the molecular weight (MW) and the molecular weight distribution (MWD) of the PS blocks varied with the PDMS block length (block MW) comprising the macroinitiators, and the styrene conversion level. As the PDMS block length or the conversion level …
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DIFFUSION CONTROLLED VINYL POLYMERIZATION
… well known that the polymerization rate and the molecular weight distribution of vinyl polymers can change markedly during the course of polymerization and that these changes are due to the influence of self-diffusion upon the termination reaction. This phenomenon is commonly referred to as the …
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Synthesis and Characterization of Linear and Branched Polylactic Acid for Use in Food Packaging Applications
<p>Polylactic acid (PLA) resins of various molecular weights and molecular weight distributions were synthesized. Linear, narrow molecular weight distribution (MWD) PLA resins were synthesized, as well as resins containing both high molecular weight branched structures and low molecular weight …
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Polymeranaloge Carbanilierung von Cellulose
Characterization of cellulose by its molecular weight distribution is afforded after polymeranalogeous dissolution. Additionally, a molecular dispersion of the polymer is a prerequisite. Common processes are dissolution of cellulose in dimethylacetamide-lithiumchloride, nitration and carbanilation. …
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