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Showing 1 to 12 of 12 for “"polyureas"”.
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Polydimethylsiloxane Modification of Segmented Thermoplastic Polyurethanes and Polyureas
… aminoalkyl functional PDMS based segmented polyureas are described herein. Two-phase morphology was observed for all the polyurea samples, even when the hard segment concentration was as low as 6wt%. All these polyureas formed clear transparent films that exhibited good mechanical properties …
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Isocyanate-derived organic aerogels: polyurethanes, polyureas, polyamides and polyimides
… with (a) alcohols (polyurethanes); (b) water (polyureas); (c) carboxylic acids (polyamides); and, (d) acid anhydrides (polyimides). All processes are invariably single-step, one-pot and take place at room temperature or slightly elevated temperatures. The resulting materials are robust, they …
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Siloxane-Based Reinforcement of Polysiloxanes: from Supramolecular Interactions to Nanoparticles
… printing processes with promising results. PDMS polyureas represent an important class of elastomers with unique properties derived from the synergy between the nonpolar nature, unusual flexibility, and low glass transition temperature (Tg) afforded by the backbone siloxane linkages (-Si-O)n- of …
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Novel Monomer Design for Next-Generation Step-Growth Polymers
… thermoplastics in the form of bio-based polyureas exhibited mechanical properties similar to those of non-bio-based polyureas. The isocyanate-free synthetic route incorporated an essential urea degradation mechanism at elevated temperatures to produce isocyanic acid, which then reacted …
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Structure–Property Relationships Of: 1) Novel Polyurethane and Polyurea Segmented Copolymers and 2) The Influence of Selected Solution Casting Variables on the Solid State Structure of Synthetic Polypeptide Films Based on Glutamate Chemistry
… characterization of segmented polyurethanes and polyureas synthesized without the use of chain extenders'molecules that are typically used to promote a microphase separated morphology that gives these materials their useful characteristics. Polyurethanes in which a single asymmetric diisocyanate …
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High Performance Engineering Polymers: Design, Properties, and Performance
… polysulfones, polyesters, polyimides and polyureas. Copolymers ranging from random to segmented sequences provided insight into the influence of segment length on physical properties. Melting temperatures, glass transition temperatures, and mechanical properties responded systematically to …
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Functional Polymer Materials: From Iptycenes to Ring-Opening Polymerizations
… platform with access to a diversity of polyureas and polythiocarbamates. In Chapter 4, we seek to synthesize a dibenzobarrelene-elaborated polyacetylene, whereby the dibenzobarrelene groups can provide stability by steric shielding, as well as a site for attaching solubilizing and …
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Siloxane modified polyurea and polyurethane urea segmented copolymers
… strength and better thermal stability than polyureas based on commercial PPO which contains some terminal unsaturation. This was attributed to the achievement of both higher molecular weight and to more extensive microphase separation between the segments. In addition, the surface structure …
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Designing Multiphase Step-Growth Polymers for Advanced Technologies: From Electromechanical Transducers to Additive Manufacturing
… approach facilitated the synthesis of segmented polyureas with tunable thermal and mechanical properties. These materials found use as high dielectric elastomers and water-soluble polymers for extrusion-based AM dependent on the backbone composition. Vat photopolymerization (VP) AM served as a …
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Molecular investigation of the wood/pMDI adhesive bondline
… is a heterogeneous complex of urethanes, polyureas, residual isocyanates and biurets. The network structure is controlled by the curing variables such as temperature and time. Urethane formation was detected under relatively mild cure conditions. Thermal decomposition of urethanes (120°C) …
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Tailoring Siloxane Functionality for Lithography-based 3D Printing
… chain extender and urea afforded isocyanate-free polyureas in the absence of solvent and catalyst. Dynamic mechanical analysis (DMA) measured multiple, distinct α-relaxations that suggested microphase separation. This work leverages the unique properties of PDMS and provides multiple chemistries …
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Exploring Multiple Hydrogen Bonding and Ionic Bonding in the Design of Supramolecular Polymers
… manufacturing. The molecular design of the polyureas featured soft segments containing flexible polyether chain and a relatively weak urea hydrogen bonding sites in the soft segment and rigid UCyt hydrogen bonding groups in the hard segment. The reversible characteristics of QHB enabled low …