Polyurethane microspheres

Li B, Yoshii T, Hafeman AE, Nyman JS, Wenke JC, Guelcher SA. The effects of rhBMP-2 released from biodegradable polyurethane/microsphere composite scaffolds on new bone formation in rat femora. Biomaterials 2009 30(35) 6768-6779. 

A variety of stabihzers, including reactive diol containing two primary hydroxyl groups with a long hydrophobic moiety (e.g., PLMA) (Fig. 5.3a), an amphiphilic block copolymer (Fig. 5.3b) and graft copolymer (Fig. 5.3c) have been used in the preparation of polyurethane microspheres or microcapsules in nonaqueous medium [15-17,19-24]. 

Lin CY, Hsu SH. Fabrication of biodegradable polyurethane microspheres by a facile and green process. J Biomed Mater Res Part B Appl Biomater 2014. [onhne] Available at http //onlinelibrary.wiley.eom/doi/10.1002/jbm.b.33266/pdf. [accessed 03.08.14]. 

Jabbari E, Khakpour M. Morphology of and release behaviour from porous polyurethane microspheres. Biomaterials 2000 21 2073-89. 

Tong F, Chen X, Chen L, Zhn P, Lnan J, Mao C, et al. Preparation, blood compatibility and anticoagnlant effect of heparin-loaded polyurethane microspheres. J Mater Chem B 2012 l(4) 447-584. 

No.20, Oct.2000, p.2073-9 MORPHOLOGY OF AND RELEASE BEHAVIOUR FROM POROUS POLYURETHANE MICROSPHERES... 

Ramanathan LS, Shukla PG, Sivaram S. Synthesis and characterization of polyurethane microspheres. Pure Appl Chem 1998 70 1295-1299. 

Syntactic foamed plastics (from the Greek ovvxa C, to put together) or spheroplastics are a special kind of gas filled polymeric material. They consist of a polymer matrix, called the binder, and a filler of hollow spherical particles, called microspheres, microcapsules, or microballoons, distributed within the binder. Expoxy and phenolic resins, polyesters, silicones, polyurethanes, and several other polymers and oligomers are used as binders, while the fillers have been made of glass, carbon, metal, ceramics, polymers, and resins. The foamed plastic is formed by the microcapsular method, i.e. the gas-filled particles are inserted into the polymer binder1,2). 

A family of elastomeric foams has been developed by Rand 129) for use as stress relief coatings on electronic components in encapsulated electronic assemblies. Polysulfide, silicone and polyurethane elastomers blended with glass and phenolic microspheres have been used to formulate syntactic foams (Fig. 10) These foams are used to minimize the stress caused by differential thermal expansion between the component and the encapsulant. 

The polyurethane (PU) can be considered an environment-friendly material because the urethane bond resembles the amide bond, which implies possible biodegradability. It can be used in various elastomer formulations, paints, adhesives for polymers and glass, and artificial leather as well as in biomedical and cosmetic fields. Polyurethane spheres were prepared from 20/40% of PU prepolymer solution in xylene [91]. PU droplets were formed in water with the SPG membrane of different pore size (1.5-9.5 pm) and then polymerized to form the final microspheres. Finally, spherical and solid PU particles of 5 pm were obtained after the removal of the solvent. In another study, Ma et al. reported the formation of uniform polyurethane-vinylpolymer (PUU-VP) hybrid microspheres of about 20 pm, prepared using SPG membranes and a subsequent radical suspension polymerization process [92], The prepolymers were solubilized in xylene and pressed through the SPG membrane into the continuous phase containing a stabilizer to form uniform droplets. The droplets were left for chain extension at room temperature for some hours with di- and triamines by suspension polymerization at 70 °C for 24h. Solid and spherical PU-VP hybrid particles with a smooth surface and a higher destructive strength were obtained. 

Polyurethane [117] and polyester [118] particles have also been prepared by the dispersion polyaddition of ethylene glycol (EG) and toluene diisocyanate (TDI) in paraffin, and the polycondensation of acid and ester at a high polymerization temperature, respectively. Table 3 provides an overview of microspheres of monomers other than vinyl monomers obtained by dispersion polymerization. 

The matrix is considered to be the binder for the microspheres. Typical matrix materials include (a) thermosetting resins such as epoxy resins, unsaturated polyesters, vinyl esters, phenolics, polyurethanes, and silicones (b) thermoplastic resins such as polyethylene, polystyrene, polyvinyl chloride (c) asphalt and (d) gypsiun and cement. 

As mentioned in the previous section, hollow zeolite spheres of LTA, FAU, BEA, MFI can be prepared in the presence of polystyrene beads as templates by using an LBL self-assembly technique. Recently, several research groups have tried to adopt similar methods to synthesize zeolite-template composites on the surfaces of templates with various shapes and sizes, properties, and structures through self-assembly or in situ-crystallization approaches. Subsequent removal of the templates forms zeolite materials with analogical skeletons of the templates. Up to now, the reported templates include microspheres, carbon fibers, polyurethane foams, and microbe structures,[144,145] as well... 

MAJOR POLYMER APPLICATIONS microspheres PVC, pol)mrethanes, polyester, silicone, acrylics, epoxy, rubber PTFE powders PA, POM, PC, polyesters, PI, PSF, PSO, PPS, polyurethanes, ECTFE, EPDM, SBR, fluorosilicones, NR... 

Ski boots use a wide variety of plastics adapted for low temperatures. Thermoplastic polyurethane/ABS blends and plyamides are used for the outer shell of ski boots and modified polyethylene terephthalate for the binding. Polyurethane (PU) foam is often used to line the boots. Microsphere fillers may be incorporated into foam-lined boots to add further thermal insulation to the wax binder. The antivibrational characteristics of PU foams have also led to their use in ski fittings. A sandwich construction of polyurethane elastomer and aluminum alloy has been fitted between the ski and the binding to reduce shock and vibration. 

Amphiphilic peptides lonically crosslinked micro- and nano-spheres Biotinylated microspheres Photopolymerizable hydrogels Thermally activated crosslinked gels Two-component polyurethanes Alginates... 

A syntactic foam produced by mixing a polyurethane compound with millions of tiny gas-filled microspheres has been used for high-performance footballs. Developed by the sports company Adidas and Bayer, the foam makes up the top one-third of the outer skin of the footballs. When a football is kicked, the microspheres restore its shape very quickly, producing a very high elastic recovery compared with other football constructions, with the effect that the ball deviates very little from its initial flight path. 

Liu H, et al. Hydroxyapatite/polyurethane scaffold incorporated with drug-loaded ethyl cellulose microspheres for bone regeneration. J Biomed Mater Res B Appl Biomater 2010 95(1) 36 6. 

Elastomeric polyurethane RIM, two-component MDI-based liquid systems available unfilled, glass-filled or mineral/microsphere filled offering large part mouldability, superior impact strength and excellent surface quality and in-mould coating, for agriculture, construction, automotive and special transportation application. 

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