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Showing 1 to 20 of 43 for “"Polyurea"”.
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Viscoelastic characterization of polyurea based polymers
Several formulations of sprayed polyurea were considered as an alternative to cast polyurea. Based on results from confined compression experiments on these materials, TRI – 25 was selected as the best alternative material on account of its good flow characteristics at lower stresses. The …
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Energy storage and dissipation in polyurea composites
Polyurea composites have been of interest for a variety of engineering applications for their highly dissipative yet resilient behavior under deformation. Polyurea composites have been considered as a self-healing and anticorrosion coating in building applications,and more interestingly, as a …
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Polyurea aerogels: From nanoscopic to macroscopic properties
… quantitatively. In this context, polyurea aerogels were chosen as a model system with demonstrated potential for rich nanomorphology and being guided by a statistical Design-of-Experiments model, a large array of materials (208) with identical chemical composition, but quite …
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Energy storage and dissipation in polyurea composites
Polyurea composites have been of interest for a variety of engineering applications via their highly dissipative yet resilient behavior under deformation. Polyurea composites have been considered as a self-healing and anticorrosion coating in building applications, and more interestingly, as a …
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Physical, Mechanical and Chemical Aging of Polyurea Nanocomposites
Two component polyurea systems, on one hand, are gaining popularity as corrosion and abrasion resistant coatings and linings while on the other hand there are a few polyurea compositions being used as barrier against blast and ballistic threats to protect nation's critical infrastructure. Physical …
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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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Nanoenhanced Polyurea As A Blast Resistant Coating For Concrete Masonry Walls
… retardant. This thesis focuses on nanoenhanced polyurea for applications in improving blast resistance, while possessing improved flame retardancy, of concrete masonry walls. The polyurea that is being researched is enhanced with nanoadditives in an effort improve both blast and fire resistance. …
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Finite strain behavior of polyurea for a wide range of strain rates
Polyurea is a special type of elastomer that features fast setting time as well as good chemical and fire resistance. It has also good mechanical properties such as its high toughness-to-density ratio and high strain rate-sensitivity, so its application is recently extended to structural purpose to …
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The Manufacturing and Ballistic Testing of Tri-axial Quasi Three Dimensional Woven Composites Layered in Polyurea
… quasi 3D tri-axial woven composite layered with polyurea against high power rifle bullet impact. This is done by evaluating the effectiveness of quasi-3D tri-axial woven composites in resisting .50 caliber rifle rounds and utilizing a high speed camera to visually inspect the self-sealing …
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Behavior of reinforced concrete column-beam joint subjected to close in blast loads with polyurea and FRP sheets
… elastic at this charge level. Application of polyurea coatings significantly reduces peak stresses (30–40 %) and suppresses spalling through viscoelastic energy dissipation. FRP sheets also show overall suppression of damage in the structure. Results demonstrate that protective coatings offer …
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Structure-Property Relationships of Flexible Polyurethane Foams
… polyurethane foam systems, of lamellae-like polyurea structures ca. 0.2 mm long and ca 5-10 nm across. Aggregations of these lamellae-like hard domains may be the polyurea balls typically observed via TEM. Diethanolamine, a widely used cross-linking agent in molded foams, was shown to disrupt …
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Processing and Properties of Hybrid Silane-Epoxy Nanocomposite Coatings
… films were improved by blending it with aromatic polyurea. This concept of hybrid composition of epoxy ester and polyurea is novel and has never been applied before. The glass transition temperature of the epoxy ester films was increased from nearly 30°C to 140°C in the hybrid composition. The …
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Energy dissipation in shape memory zirconia particles, packings, and composites
… particles, composites were fabricated using polyurea as a matrix material, and the bonding between the zirconia particles and polyurea matrix was studied along with mechanical properties. Finally, the effect of high strain rate impact was observed on ceria-doped zirconia pellets using laser …
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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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Investigation of the Influence of Selected Variables on the Solid State Structure-Property Behavior of Segmented Copolymers
… polyurethane, polyurethaneurea, and polyurea copolymers is explored. The specific variables which have been utilized singly or in conjunction with others are hard segment crystallizability, crystallization conditions, hard segment content, soft segment type and molecular weight, …
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One pot synthesis of metal, carbides and polymeric aerogels
… a new efficient method for the synthesis of polyurea (PUA) aerogels by reaction of di or triisocyanates with controlled amounts of water, resulting in in-situ amine formation, which reacts further with yet-unreacted isocyanate to form polyurea. PUA aerogels prepared by this method have …
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NOVEL SYNTHETIC METHODS AND APPLICATIONS OF POROUS MATERIALS: AEROGEL FOAMS, METALLIC AEROGELS, AMORPHOUS AND GRAPHITIC CARBON AEROGELS
… metallic Co(0) aerogels were synthesized from polyurea-crosslinked cobaltia xerogel powder compacts via carbothermal reduction, for application as thermites. III. Carbon aerogels were synthesized from compressed compacts of polyurea- and polyacrylonitrile-crosslinked silica xerogel powders. The …
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Microencapsulation of reactive amines and isocyanates and their application to self-healing systems
… synthesized by interfacial polymerization of a polyurea about a droplet of amine by means of suspension polymerization. Capsules are subsequently isolated and analyzed for content, and shown to contain reactive amine. The microcapsules containing reactive amine are employed in concert with …
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Molecular orientation and relaxation behavior in flexible water- blown polyurethane foams
… molded plaques as well as a chemically similar polyurea-urethane elastomer, PUUE, were studied to better understand the relaxation behavior and the molecular orientation upon deformation in these systems. The two main experimental techniques used in this investigation were stress relaxation in …
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Synthesis and applications of ceramic (silicon carbide and silicon nitride), metallic (cobalt(0)) and polymeric (polyurethane) aerogels
… were prepared from compressed compacts of polyurea-crosslinked silica xerogel powders. The process is time efficient as solvent-exchange through powders is fast, and energy efficient as it bypasses drying with supercritical fluids. The final ceramic objects were chemically pure, sturdy, …
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