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Showing 1 to 20 of 33 for “"siloxanes"”.
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Occurrence of cyclo-siloxanes in wastewater treatment plants - quantification and monitoring
Siloxanes are persistent, bio-accumulative and toxic emerging contaminants introduced to wastewater from common healthcare and biomedical products, and various industrial processes. They remain unchanged through wastewater treatment and a considerable portion ends up in surface waters through …
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Investigating escape of low MW siloxanes from PDMS matrix in aqueous solution
… an oxygen sensor made from low molecular weight siloxanes (LMWS) in a PDMS matrix can be implanted during a biopsy and effectively measure oxygen levels in rat tumors with MRI. The Cima group also found that the sensors experienced signal loss over time when stored in air. The purpose of this …
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Experimental and theoretical investigations of the dielectric and electro-optical properties of polycarbazoles and polysiloxanes
… fractions of cyclic and linear poly(dimethyl siloxanes), a comparative dielectric study has been undertaken of these materials. The electronic, atomic and orientational polarizations have been determined in the undiluted state for number-average molar masses in the range 160-7700 and dipole …
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Functionalization of Metal Oxide Surfaces through Chemical Reactions and Physical Adsorption
… <p>We began with Methyl-terminated poly(dimethylsiloxanes) (PDMSs), which are typically considered to be inert and not suitable for surface functionalization reactions because of the absence of readily hydrolysable groups. Nevertheless, these siloxanes do react with silica and other oxides, …
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Method Development for the Synthesis of Anaerobic Digester Biogas with the Laboratory Environment
… energy potential associated with its combustion. Siloxanes, a family of volatile organic silicon compounds, pose large impediments to biogas usage due to the formation and precipitation of silicon dioxide within combustion devices. Removal of siloxanes prior to combustion is therefore a growing …
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Synand characterisation of silicone based mesophase forming materials.
… a range of novel cyclic and linear mesogenic siloxanes. A synthetic strategy based upon the synthesis of linear side-chain siloxanes was adopted. End-functionalised linear siloxane precursors were synthesised via ring opening polymerisation reactions. The coupling of mesogen and siloxane was …
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TEM/EDXS studies of phase separation in block and graft copolymers
… domains formed in alternating poly(ester/siloxanes), and phase mixing seemed to correlate with the solubility parameters of the three siloxane types. Shear-stresses during molding changed domain shapes and eliminated short-range ordering. In the PMMA-graft-dimethyl siloxane system, SK, 10K …
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The modification of polymeric materials with plasticizers or elastomers
… apparent compatibility between the epoxy and the siloxanes was enhanced by increasing methyltrifluoropropyl or diphenyl siloxane content or lowering molecular weight, resulting in profound changes in morphology and the resultant mechanical properties of the modified resins. Fracture toughness was …
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Synthesis and characterization of polycarbonate-polydimethylsiloxane block copolymers
… were obtained using the hydroxyl-terminated siloxanes in two cases: 1, when siloxanes of <Mn> ≃ 5000 g/mole were used and, 2, when the siloxane oligomers were capped with the dichloroformate of bisphenol-A prior to the interfacial step. When these phase transfer catalyzed reactions were …
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Synthesis, characterization, and evaluation of a heat stabilizing siloxane
<p>Siloxanes, renowned for their heat resistance and release properties, are prone to oxidize above 200°C. The goal herein is to increase siloxane bath life used in fuser roll applications at temperatures above 200°C, yielding faster production, less waste, and cost savings by keeping the bath …
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Octopus and dendrimer molecules with silsesquioxane cores
… of 1-alkenes and vinyl-functional siloxanes by T<sub>8</sub> hydrogen silsesquioxane, (HSiO<sub>3/2</sub>)<sub>8</sub>, has been demonstrated. The chemistry of addition was studied, and it was found that while the addition of the I-alkenes to T<sub>8</sub> was, regioprecise with …
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Capillary supercritical fluid chromatography
… polyethylene glycol pyrolysis or by mixed cyclic siloxanes. Both gave better reproducibility than an untreated column but the overall reproducibility of the polyglycol deactivation was better than the cyclic deactivation. Liquid CO₂ extraction was performed on a variety of spices and food …
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Magnetic resonance imaging contrast agents for chemical sensing
… were made by encapsulating low molecular weight siloxanes in a polydimethylsiloxane (PDMS) matrix. The PDMS matrix is biocompatible and prevents clearance of the contrast material. The longitudinal relaxation time, T1, of these agents is proportional to the amount of dissolved oxygen in the …
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Deactivation and preparation of fused silica open tubular columns for gas and supercritical fluid chromatography
… mixtures of commercially available cyclic siloxanes were shown to be a viable alternative to the use of dichlorosilanes as starting material. The main advantages were the simplification of the synthesis procedure, simpler and better molecular weight control of the polymer, and the …
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PPE Effectiveness in Agricultural Settings
… chlorpyrifos, chlorpyrifos oxon, pentadecane, siloxanes and trimethyl benzene. The concentrations of the compounds were measured, and the frequency of breakthrough was calculated for each kind of media. A mass-to-mass ratio, comparing the ambient concentrations from the cartridge …
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The ring-opening polymerization of cyclosiloxanes in the presence of bis ([alpha], [omega]-aminopropyl)-1,3-tetramethyldisiloxane
… towards blockiness. A series of polyester-siloxanes was prepared using both bulk and solution polycondensation techniques. Copolymers based on polybutylene terephthalate were highly insoluble, due to the presence of crystallinity in the systems. The incorporation of some isophthalate …
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The synthesis and characterisation of novel long chain dimethyl siloxane surfactants.
… polydimethylsiloxane chain. Polydimethylsiloxanes are low melting materials (glass transition at ca -120°C) with very flexible chains, hence surfactants based on them might be readily soluble in water. This project involves chemical attachment of amphiphilic mesogens to alpha-SiH …
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Large Polymers that Behave Like Small Polymers
… flexible monomer units like ethylenes and siloxanes create soft, flexible plastics at the expense of thermal and mechanical robustness. Synthesizing polymers with novel architectures can overcome these challenges by creating materials with a unique set of properties and thus eliminating the …
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Characterization of botryococcus sp. and identification of carbohydrates metabolic related enzymes toward lipid production
… cyclohydrocarbons, nitrogenated hydrocarbons, siloxanes, phenols and phenol derivatives. A glycolytic enzyme ‘Enolase ’which can generate phosphoenolpyruvate (PEP) and then convert it into pyruvate was identified in this study. Enolase which helps in high lipid metabolism was found in the …
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Synthesis and Characterization of Wholly Aromatic, Water-Soluble Polyimides and Poly(amic acid)s Towards Fire Suppression Foams
… their modification with phosphonium moieties or siloxanes, which are slated to have positive effects on performance. Overall, these sPIs and sPAAs provide a promising platform for the future direction of fire suppression foams.
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