نتایج جستجو برای: polyurethanes
تعداد نتایج: 2596 فیلتر نتایج به سال:
Polyurethanes are the most well known polymers used to make a binder in high energy material. Polyurethanes aregenerally synthesized by the reaction of diisocyanates and polyols and chain extender.These polymers are often two-phase morphology.Chain extenders are small diols or diamines that are inserted to the hard segment of of polyurethane chain. chemical structure of chain extender, the ...
In this Article, we studied the enzymatic hydrolytic biodegradation behavior of a novel multiblock thermoplastic polyurethane (TPU) system, which incorporates polyhedral oligomeric silsesquioxane (POSS) into linear biodegradable thermoplastic polyurethanes containing poly(ε-caproactone) (PCL) and polyethylene glycol (PEG) blocks. The biodegradation behavior of POSS-PCL-PEG TPUs was characterize...
Introduction: Polyurethanes (PU) have long been used for biomedical applications due to their excellent mechanical properties and reasonable biocompatibility. However, polyether urethane elastomers are susceptible to biodegradation. Silicones are known to be biostable and biocompatible, making them an ideal replacement for the polyether soft segment of polyurethanes. As a result, a new silicone...
Nitric oxide (NO) has been shown to exhibit significant anti-platelet activity and its release from polymer matrices has been already utilized to increase the biocompatibility of various blood-contacting devices. Herein, details of a new synthetic approach for preparing NO-releasing diazeniumdiolated polyurethanes (PU) are described. The method's utility is demonstrated by the incorporation of ...
A novel polyurethane was successfully synthesized by chain-extension of biodegradable poly (l-lactide) functionalized phosphatidylcholine (PC) with hexamethylene diisocyanate (HDI) as chain extender (PUR-PC). The molecular weights, glass transition temperature (Tg) increased significantly after the chain-extension. The hydrophilicity of PUR-PC was better than the one without PC, according to a ...
Multilayered thin films prepared with the layer-by-layer (LBL) assembly technique are typically "brittle" composites, while many applications such as flexible electronics or biomedical devices would greatly benefit from ductile, and tough nanostructured coatings. Here we present the preparation of highly ductile multilayered films via LBL assembly of oppositely charged polyurethanes. Free-stand...
A significant imperfection of parts made from linear block-polyurethanes under conditions friction contact in the presence water medium is an intensification hydrolysis processes and reduction bulk strength. In order to slow down process, samples polyurethanes were subjected three types thermal impacts: processing during some time, infrared laser irradiations. It has been established that field...
polyurethanes (purs) are polymers that can be generated by a step-growth polyadditionreaction of diisocyanates with polyols. the number of well-developed chemical procedures applicable to theirmanufacture, and the diversity of chemical structures in which polyurethanes can be built, account for thewidespread use of these materials in the last few decades for both domestic and technical applicat...
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