In polyurethane nanocomposites

James Korley LT et al (2006) Preferential association of segment blocks in polyurethane nanocomposites. Macromolecules 39(20) 7030-7036... 

Khan F, Dahman Y. A novel approach for the utilization of biocellulose nanoflbres in polyurethane nanocomposites for potential applications in bone tissue implants. Des Monomers Polym April 2012 15(l) l-29. 

Fong N, Poole-Warren LA, Simmons A. Development of sustained-release antibacterial urinary biomaterials through using an antimicrobial as an organic modifier in polyurethane nanocomposites. J Biomed Mater Res B Appl Biomater 2013 101B 310-9. http //dx.doi.Org/10.1002/jbm.h.32841. 

Sarier, N. and E. Onder. 2010. Organic modification of montmoiillonite with low molecular weight polyethylene glycols and its use in polyurethane nanocomposite foams. Thermo. /4cto 510 113-121. 

There are few reports on block-copolymeric TPE (namely, polyurethane, EVA, SBS, poly (styrene-fo-butyl acrylate) (PSBA))-clay nanocomposites also [196-199]. Choi et al. [196] studied the effect of the silicate layers in the nanocomposites on the order-disorder transition temperature of... 

Fabrication methods have overwhelmingly focused on improving nanotube dispersion because better nanotube dispersion in polyurethane matrix has been found to improve the properties of the nanocomposites. The dispersion extent of CNTs in the polyurethane matrix plays an important role in the properties of the polymer nanocomposites. Similar to the case of nanotube/solvent suspensions, pristine nanotubes have not yet been shown to be soluble in polymers, illustrating the extreme difficulty of overcoming the inherent thermodynamic drive of nanotubes to bundle. Therefore, CNTs need to be surface modified before the composite fabrication process to improve the load transfer from the polyurethane matrix to the nanotubes. Usually, the polyurethane/CNT nanocomposites can be fabricated by using four techniques melt-mixing (15), solution casting (16-18), in-situ polymerization (19-21), and sol gel process (22). 

Several main synthesis methods widely applied to produce carbon nanotube-polyurethane nanocomposites were summarized above. In addition, latex technology (27), thermally induced phase separation (28), electrospinning (29,30) and many other methods also show their own advantages and promises, however, these methods will not be discussed here. 

It is difficult to fully utilize the mechanical or electrical properties of CNTs in their polyurethane nanocomposites due to the difficulty... 

The viscoelastic properties of carbon nanotube/polymer composites have both practical importance related to composite processing and scientific importance as a probe of the composite dynamics and microstructure. The viscosity for CNT/PU dispersion at mixing is also very important for in-situ formation of polyurethane nanocomposite. Lower viscosity means a better flow ability and more homogenous mixing with isocyanate. Furthermore, low viscosity is very helpful to remove the bubbles before curing, which is a key step for polyurethane preparation. 

The unique two-phase structures of polyurethane that offers the elasticity of rubber combined with the toughness and durability of metal make them one of the most extensively studied and frequently used materials in carbon nanotube related nanocomposites. The main difficulty in developing CNT based polyurethane nanocomposites was how to achieve uniform and homogeneous CNT dispersion. Further investigations on the interactions between carbon nanotubes and two-phase structures are critical for the wider applications of carbon nanotube/polyurethane composites. 

Metal-containing nanocomposites were obtained by dispersion of metal chlorides in polyurethane. Both polyurethane and metal salts were dissolved in... 

Pei, A H., Malho, J. M., Ruokolainen, J., Zhou, Q., and Berglund, L. A (2011). Strong nanocomposite reinforcement effects in polyurethane elastomer with low volume fraction of cellulose nanocrystals. Macromolecules. 44,4422-4427. 

Abstract This chapter describes vegetable oil-based polymer nanocomposites. It deals with the importance, comparison with conventional composites, classification, materials and methods, characterisation, properties and applications of vegetable oil-based polymer nanocomposites. The chapter also includes a short review of polymer nanocomposites of polyester, polyurethanes and epoxies based on different vegetable oils and nanomaterials. The chapter shows that the formation of suitable vegetable oil-based polymer nanocomposite can be considered to be a means of enhancing many of the desirable properties of such polymers or of obtaining materials with an intrinsically new set of properties which will extend their utility in a variety of advanced applications. Vegetable oil-based shape memory hyperbranched polyurethane nanocomposites can be sited as an exampie of such advanced products. 

The cytocompatibility of polyurethane nanocomposites is generally studied from red blood cell (RBC) haemolysis inhibition data obtained from the anti-hemolytic test described in Chapter 2. In most of the reported cases, vegetable oil-based polyurethane nanocomposites exhibit better haemolysis prevention against harmful free radicals than do their respective pristine polyurethanes. These observations indicate that the presence of nanomaterial in the nanocomposites plays a crucial role in RBC haemolysis prevention. 

Electrical properties such as conductivity, resistivity, I (current)-V (voltage) characteristics of vegetable oil-based polyurethane nanocomposites are sometimes influenced by nanocomposite formation with a suitable nanomaterial. BaTiOs superfine fibre-filled castor oil-modified polyure-thane/poly(methyl methacrylate) interpenetrating polymer network nanocomposites exhibit an increase in conductivity between insulator and semiconductor with an increase in nanofibre loading. ... 

Tetraethoxyorthosilane and linseed oil polyol silica embedded polyurethane nanocomposites were obtained by a sol-gel technique. The polyol/ silica nanoparticles network showed a strong interaction with uniform, spherical silica nanoparticles of 2-30 nm size embedded in the polymer matrix. The system was further reinforced by 2 wt% and 5 wt% fumed silica. The resultant systems showed improved thermal stability with mild to moderate antibacterial behaviour against E. coli and S. aureus. 

A series of castor oil polyurethane/poly(methyl methacrylate) interpenetrating polymer networks (IPNs) and gradient IPNs, cured at room temperature, were prepared by a simultaneous IPN method, and nanocomposites with BaTiOs superfine fibre were reported for the systems. A dose-dependent improvement in thermoelectric and mechanical properties was observed in the nanocomposites compared to the pristine systems. 

There are other examples of applications of vegetable oil-based nanocomposites in different fields. These include soybean oil-based PU/silica nanocomposites as surface coating materials, anti-corrosive polyurethane/ OMMT coatings for carbon steel and palm oil, soybean oil and castor oil-based polyurethane nanocomposite as foams. - - - ... 

J. M. Herrera-Alonso, E. Marand, J. C. Little, S. S. Cox, Transport properties in polyurethane/ clay nanocomposites as barrier materials Effect of processing conditions, J. Membr. Sci., 337, 208-214 (2009). 

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