Layered Silicate Nanoreinforcements

Clays are strongly hydrophilic in nature, making their dispersion in organic matrices difficult [26]. There are usually three possible arrangements of these layered silicate clays, which can be obtained when they are dispersed in a polymer matrix. If the polymer cannot intercalate between the silicate sheets, a non-intercalated microcomposite is obtained. Beyond this traditional class of polymer-filler composites, two other types of composites can be obtained. An intercalated structure is one in which the separation of clay layers occurs to some extent by increasing the interlayer spacing. 

The last one is an exfoliated or delaminated structure where there is complete separation of clay platelets into random arrangements. This is the ideal nanocomposite arrangement but is harder to achieve during synthesis and/or processing. For this successful dispersion organophili-zation is essential for successful exfoliation of hydrophilic clays in most 

In Situ Polymerization Template Method Solvent Mixing Melt Mixing Solid State Mixing 

A practical study where CaCOj/iPP nanocomposite was applied for packaging of apple slices showed that total microbial and mold counts decreased significantly over a period of 10 days [65] compared to apples stored in neat isotactic PP, which experienced an increase of total meso-philic microflora over the same time period. The study also showed that the apples stored in PNC packaging ripened better due to ethylene gas 

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Petersson, L., Oksman, K. Biopolymer based nanocomposites Comparing layered silicates and microcrystalline cellulose as nanoreinforcement. Compos. Sci. Technol. 66, 2187-2196 (2006)... 

Peresin MS, Habibi Y, Zoppe JO et al (2010) Nanofiber composites of polyvinyl alcohol and cellulose nanocrystals manufacture and characterization. Biomacromolecules 11 674—681 Petersson L, Oksman K (2006) Biopoljoner based nanocomposites comparing layered silicates and microcrystalline cellulose as nanoreinforcement. Compos Sci Technol 66 2187-2196... 

The two decades have witnessed an extensive research and development in the field of thermoset nanocomposites. The physics and chemistry of intercalation of clay (layered silicate) in thermoset resin have been understood to a great extent though synthesis of fully exfoliated thermoset-based nanocomposites still remains as a challenge. More research is necessary to study the feasibility of integrating the nanoreinforced thermoset resins into the fibre-reinforced plastics to develop composite structure not... 

Although effective at improving the barrier properties, layered silicates are not biodegradable. Cellulose can be a biodegradable alternative to the use of sihcates. There are two types of nanoreinforcements that can be obtained firom cellulose fibers microfibrils (cellulose chains synthesized by plants or animals) and nanowhiskers (isolated crystalline... 

The comprehensive flame retardation of polymer-clay nanocomposite materials was reported by Dr. Jeff Gilman and others at NIST [7]. They disclosed that both delaminated and intercalated nanoclays improve the flammability properties of polymer-layered silicate (clay) nanocomposites. In the study of the flame retardant effect of the nanodispersed clays, XRD and TEM analysis identified a nanoreinforced protective silicate/carbon-like high-performance char from the combustion residue that provided a physical mechanism of flammability control. The report also disclosed that The nanocomposite structure of the char appears to enhance the performance of the char layer. This char may act as an insulation and mass transport barrier showing the escape of the volatile products generated as the polymer decomposes. Cone calorimetry was used to study the flame retardation. The HRRs (heat release rates) of thermoplastic and thermoset polymer-layered silicate nanocomposites are reduced by 40% to 60% in delaminated or intercalated nanocomposites containing a silicate mass fraction of only 2% to 6%. On the basis of their expertise and experience in plastic flammability, they concluded that polymer-clay nanocomposites are very promising new flame-retarding polymers. In addition, they predict that the addition... 

Bionanocomposites of PHBV reinforced with hydroxyapatite nanoparticles have been studied and compared to nanoclays-reinforced PHBV [254-257]. Maiti and Yadav [254] prepared bionanocomposites based on PHBV reinforced with layered silicate and hydroxyapatite by melt extrusion. The nanostructure, as observed from WAXS and TEM, indicated intercalated hybrids for layered silicates and uniformly distributed hydroxyapatite nanoparticles which conferred improvement in thermal and mechanical properties as compared to the neat copolymer. The layered sihcate nanocomposites exhibited superior mechanical properties as compared to hydroxyapatite bionanocomposites. It was also found that the rate of biodegradation of the copolymer was enhanced dramatically with both nanoreinforcements, and the hydroxyapatite bionanocomposite showed the highest rate of biodegradation. 

F.M. Uhl, S.P. Davuluri, S.C. Wong, D.C. Webster, Polymer films possessing nanoreinforcements via organically modified layered silicate , Chem. Mater., 2004, 16, 1135-1142. 

Ethylene propylene diene rubber is a well-known general-purpose rubber with a significant commercial importance. It has been one of the main mbbers to be investigated with organo-treated layered silicates to study the effects of nanoreinforcement on properties.EPDM nanocomposites with clays have been prepared by simple static mixing in confined chamber such as Haake, solution blending, and on a laboratory two roll mill. However, most EPDM/clay nanocomposites have been produced by conventional, internal melt blending process. " ... 

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