Sepiolite Polymer-clay nanocomposites

In this contribution, we intend to introduce recent work dedicated to polymer-clay nanocomposites based on sepiolite and palygorskite fibrous silicates. We will consider as a priority the role of the interface between the mineral surface and the polymer matrix. In fact, this type of clay is markedly hydrophilic because their surface is covered by hydroxyl groups, mainly silanol groups (=Si-OH) [17, 22], and therefore they are compatible with many polar polymers. However, chemical modification of the silicate surface could be necessary for adjusting their... 

This chapter reviews the use of the sepiolite/palygorskite group of clays as a nanofiller for polymer nanocomposites. Sepiolite and palygorskite are characterized by a needle-like or fiber-like shape. This peculiar shape offers unique advantages in terms of mechanical reinforcement while, at the same time, it allows to study the effect of the nanofiller s shape on the final composite properties. The importance of the nanofiller shape for the composite properties is analyzed in Section 12.2, introducing the rationale of the whole chapter. After a general description of needle-like nanoclays in Section 12.3, the chapter develops into a main part (Section 12.4), reviewing the preparation methods and physical properties of polyolefin/needle-like clay nanocomposites. 

Bilotti, E. 2009. Polymer/sepiolite clay nanocomposites. PhD thesis. Queen Maiy University of London, London, U.K. 

Certain polymers of interest for potential use as ion-conductors, such as PEO, largely studied in layered clay nanocomposites [229, 232-235, 237], could also be assembled with sepiolite. Thus, PEO can be assembled with sepiolite either from solution in acetonitrile or from the melt by microwave irradiation, giving rise to nanocomposites in which a partial penetration of the polymer chains takes place [17, 237]. Further attempts recently reported focus on the modification of the physical characteristics of PEO-sepiolite composites by controlled modulation of the silicate interphase afforded by the incorporation of polyethylene glycol and other additives [246]. However, to our knowledge, no studies to date have addressed the use of PEO-fibrous clays as ion-conducting systems. 

In the chapter Dispersion of Inorganic Nanoparticles in Polymer Matrices Challenges and Solutions, the synthesis, properties, and applications of nanoparticles their surface modification and preparation of polymer-inorganic nanocomposites are reviewed in detail. The chapter Recent Advances on Fibrous Clay-Based Nanocomposites reviews recent results on nanocomposite materials derived from the fibrous clay silicates sepiolite and palygorskite and combined with diverse types of polymers, from typical thermoplastics to biopolymers such as polysaccharides, proteins, lipids, and nucleic acids. The chapter Nanohybrid Materials by Electrospinning highlights recent progress and current issues in the production of... 

Choudhury et al. [86] have studied the effect of polymer-solvent and clay-solvent interaction on the mechanical properties of the HNBR/sepiolite nanocomposites. They chose nine different sets of solvent composition and found that chloroform/methyl ethyl ketone (Qi/MEK) (i.e., HNBR dissolved in Ch and sepio-lite dissolved in MEK) is the best solvent combination for improvement in mechanical properties. XRD, AFM, , and UV-vis spectroscopy studies show that the dispersion of clay is best in the Ch/MEK solvent combination and hence polymer-filler interaction is also the highest. images shown in Fig. 14a, b clearly elucidate the aforementioned phenomena. Consequently, the tensile strength and modulus are found to be higher (5.89 MPa and 1.50 MPa, respectively) for the Ch/MEK system due to the minimum difference in interaction parameter of HNBR-solvent (xab) and sepiolite-solvent (Xcd)- Choudhury et al. have also studied the effect of different nanoclays [NA, , 15A, and sepiolite (SP)] and nanosilica (Aerosil 300) on the mechanical properties of HNBR [36]. The tensile... 

Bhattacharyya, A Sreekumar, T. liu, T. Kumar, S. Ericson, L. Hauge, H. Smalley, R. (2003) Crystallization and Orientation Studies in Polypropylene/Single Wall Carbon Nanotube Composite. Polym. Vol.44, N0.8, pp.2373-2377, ISSN 0032-3861 Bilotti, E. Fischer, H. Peijs, T. (2008) Polymer nanocomposites based on needle-like sepiolite clays Effect of functionalized polymers on the dispersion of nanofiller, crystallinity, and mechanical properties, f. Appl. Polym. Sci. Vol.107, No.2 pp.lll6-1123, ISSN 0021-8995... 

Bilotti, E., Fischer, H. R., and Peijs, T. 2008. Polymer nanocomposites based on needle-like sepiolite clays Effect of functionalized polymers on the dispersion of nanofiller, crystallinity, and mechanical properties. Journal of Applied Polymer Science 107 1116-1123. 

Keywords Bionanocomposites Bioplastics Biopolymers Clays DNA Nanocomposites Organoclays Palygorskite Phospholipids Polymers Polysaccharides Proteins Sepiolite... 

Nanocomposites based on fibrous clays provided with electrical conductivity could be designed and prepared following approaches based on the assembly of conducting polymers with fibrous clays as well as on the combination of sepiolite and palygorskite with conducting carbonaceous materials. It can be expected that future research activities in this domain will consider the combination of both approaches with the aim of optimizing the mechanical behaviour and other properties with suitable ionic and/or electronic conductivity. 

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