Nano-silica

Standard and nano silica gel, also with concentrating zone Normal phase chromatography Most frequent apphcation of all TEC layers... 

The formation of fibrils in poly(carbonate) (PC)/LCP blends have been shown to be enhanced by tbe addition of glass beads. Nano silica acts in the same way. For example, in PC/LCP blends the addition of nano silica results in a reduction of the viscosity. The reduction of viscosity is correlated with the fibrillation of tbe LCP which is promoted by nano silica. In blends of LCP and poly(sulfone) the addition of ca. 5% of nano silica effects the formation of long and perfectly orientated fibrils in the capillary flow. The nano silica forms a network in the matrix that increases the elasticity. This effect is responsible for the improvement of the formation of fibrils. 

L.-C. Wu, P. Chen, J. Chen, J. Zhang, and J.-S. He. Noticeable viscosity reduction of polycarbonate melts caused jointly by nano-silica filling and TLCP fibrillation. Polym. Eng. Sci., 47 757-764,2007. 

J. Chen, P. Chen, L. Wu, J. Zhang, andl. He. Fibrillation of liquid crystalline polymer in polysulfone promoted by increased system elasticity via adding nano-silica. Polymer, 48(14) 4242-4251, Jnne 2007. 

Hui, S., Chaki, T. K., Chattopadhyay, S., Exploring the simultaneous effect of nano-silica reinforcement and electron-beam irradiation on a model LDPE/ EVA-based TPE system. Polymer International 2009,58,680-690. 

Den Deng, S.-Q., Ye, L. Fracture behaviour of nano-silica modified epoxies at elevated temperatures. Key Eng. Mater. 312 (2006) 243-250. 

Kim D, Scibioh MA, Kwak S, Oh IH, Ha HY (2004) Nano-silica layer composite membrane prepared by PECVD for direct methanol fuel cells. Electrochem Commun 6 1069-1074... 

The formation of fibrils in poly(carbonate) (PC)/ LCP blends has been shown to be enhanced by the addition of glass beads [52,73]. Nano silica acts in the same way. For example, in PC/LCP blends the addition of nano silica results in a reduction of the viscosity... 

Figure 4. Nano silica enveloping the nano alumina structure...

Carbon nanotubes, organo-clay, nano-TiO, nano-CaCOj, nano-Al O, and nano-silica particles are all good inclusions for improving the energy absorption capability of nanocomposites, if dispersed uniformly [4]. 

Ranjbar Z, Rastegar S. Nano mechanical properties of an automotive clear-coats containing nano silica particles with different surface chemistries. Prog Org Coat 2010 72 40-3. 

Zhou, H. J., Rong, M. Z., and Friedrich, K. 2006. Effects of reactive compatibilization on the performance of nano-silica filled polypropylene composites. Journal of Materials Science Letters 41 5767-5770. 

Ruan, W. H., Huang, X. B., Wang, X. H., Rong, M. Z., and Zhang, M. Q. 2006. Effect of drawing induced dispersion of nano-silica on performance improvement of poly(propylene)-based nanocomposites. Macromolecular Rapid Communications 27 581-585. 

Nanocomposites with silica nanoparticles have been prepared in poly-dimethylsiloxanes, butadiene, styrene-butadiene, acrylonitrile-butadiene, acrylic and ethylene-propylene diene rubber. Nanocomposites in isoprene rubbers are here examined. In a nutshell, these nanocomposites were prepared adopting the three methods summarized above and nano-silica was reported to promote the mechanical reinforcement of poly (isoprene) matrices, less that CB but more than conventional silica, with lower viscosity. 

Another approach of chemical modification of silica for rubber nanocomposite for the same aim, i.e. to reduce the filler-filler interaction, is differential microemulsion polymerization. In general, the process involves two main continuous steps (i) pre-treatment/chemical bonding of silica particles with coupling agent, and (ii) polymerization of the monomer in a reaction medium containing the pre-treated silica. The resultant product is a core-shell structure where nano-silica is the core encapsulated by a nanopolymer shell. 

Polystyrene (PS)-encapsulated nano-silica has been prepared via the microemulsion polymerization technique. The PS-encapsulated silica was blended with NR, both in latex form, to finally prepare the NR nanocomposite sheets. 

NR is one of the world s important natural resources and sihca is considered environmentahy friendly upon disposal. Thus, in terms of sustainability development, development of sihca-fihed NR nanocomposites opens new opportunities for producing green materials/products such as tyres. Traditionally, carbon black is preferred over sihca as fiber in tyres due to the challenge in dispersing sihca in rubber compounds. With the new development, e.g. in situ sol gel silica, admicellar polymerization and polymer-encapsulated sihca, the applications of nano-silica in NR and modified NRs are widened. 

In terms of green composite or bio-composite, the sol-gel sihca can be applied to natural fibres. An earlier work reports the generation of sihca into the voids of kenaf fibre about 20% of nano-silica could be incorporated into the fibre. Figure 7.2 showed the incorporation of sol-gel silica in the void of kenaf fibres. The kenaf sol-gel silica mixture could be used to prepare bio-composites or green composites by choosing the right polymer matrices. 

Core-shell morphology consisting of silica as the nano-core encapsulated by polyisoprene (PIP) was prepared as the nano-shell by a differential microemulsion polymerization of isoprene on silane treated nano-silica. PIP-Si02 nanocomposite were used as an effective nanofiller in NR latex. NR filled with PIP Si02 pre-vulcanizate clearly showed an improvement in the... 

Meera et al studied the mechanical properties of NR filled with titanium dioxide (Ti02) and nano-silica composites at room temperature. It is inferred that the composites filled with silica exhibit higher tensile strength and dynamic modulus than the Ti02-filled composites due to the strong interfacial interactions of nano-silica with the NR matrix. 

---