Montmorillonite composites

Montmorillonite is a laminar and expandable clay with wet binding properties and widely available throughout the world. The layers have permanent negative charges due to isomorphic substitutions. The scientific interest of montmorillonite lies in its physical and chemical properties as well as its low price. Consequently, the industrial application of montmorillonite is an attractive process [1]. On the other hand, among numerous reports published so far, crystallization of zeolite Beta draws much attention because of its unique characteristics, in particular, acidity and acid catalysis. It is reasonable to conceive that a catalyst system based on Beta/montmorillonite composite with suitable composition should provide a good catalytic capacity. 

Beta/montmorillonite composite was prepared under dynamic hydrothermal conditions. Firstly, montmorillonite calcined at 800 °C were added to a diluted solution of sodium hydroxide, potassium chloride and TEAOH in distilled water and the resulting mixture was vigorously stirred for 1 h secondly, silica sol was added into the above uniform mixture to allow at least 3 h stirring finally, the gel was moved into stainless steel autoclaves (1L) and heated at 413 K for 48 h. The samples were characterized by XRD, N2 adsorption-desorption, FT-IR and SEM-EDS. The catalytic assessment experiments were carried out in a flowing-type apparatus designed for continuous operation. 

Figure 1 XRD pattern of Beta /montmorillonite composite (b) and calcined montmorillonite (a)...

Figure 2 shows us the N2 adsorption-desorption isotherm of Beta/montmorillonite composite. At low relative pressure a sharp adsorption of nitrogen indicates the existence of large amount of micropore. The hysteresis shown in figure 2 is ascribed to type H4 which usually can be observed on layered clay and other materials [2], It is obvious that part of the pore structure in montmorillonite is still preserved after calcination under high temperature and the following hydrothermal crystallization. 

Figure 2. N2 adsorption-desorption isotherm of Beta/montmorillonite composite...

As we have seen in the previous section, the bulk chemical compositions of montmorillonites taken from the literature are dispersed over the field of fully expandable, mixed layered and even extreme illite compositions. Just what the limits of true montmorillonite composition are cannot be established at present. We can, nevertheless, as a basis for discussion, assume that the ideal composition of beidellite with 0.25 charge per 10 oxygens and of montmorillonite with the same structural charge do exist in nature and that they form the end-members of montmorillonite solid solutions. Using this assumption one can suppose either solid solution between these two points or intimate mixtures of these two theoretical end-member fully expandable minerals. In either case the observable phase relations will be similar, since it is very difficult if not impossible to distinguish between the two species by physical or chemical methods should they be mixed together. As the bulk chemistry of the expandable phases suggests a mixture of two phases, we will use this hypothesis and it will be assumed here that the two montmorillonite... 

Let us now take a phase of montmorillonite composition (fully expandable at low temperature) and subject it to an increase in temperature and... 

Figure 9.11 Log([K+]/[H" ]) versus log[H4Si04] diagram at 25°C with plotted chemical analyses of waters in contact with clays, as reported by Aagaard and Helgeson (1983). Phase boundaries are drawn consistent with the analyses and with the illite and montmorillonite compositions proposed in the text. Agreement of the data and boundaries suggest equilibrium between the phases and support the idea that illite and montmorillonite behave as two discrete phases.AfterR.M.Garrels in C/oystfe Clay Minerals, 32 161-66, Copyright 1984.

J. C. Hutchison, R. Bissessur, and D. F. Shriver, Conductivity anisotropy of polyphosphazene-montmorillonite composite electrolytes, Chem. Mater., 8, 1597-1599 (1996). 

K.H. Chen and S.M. Yang, Polyaniline-montmorillonite composite synthesized by electrochemical method, Synth. Met., 135, 151-152 (2003). 

Jiang, L., Zhang, J., Wolcott, M.P. Comparison of polylactide/nano-sized calcium carbonate and polylactide/montmorillonite composites Reinforcing effects and toughening mechanisms. Polymer 48, 7632-7644 (2007)... 

Using clay derived from hydrated sihcates of aluminum combined with polymer materials would provide significant advantages in enhancing the physical properties compared to the use of polymers alone. The composites can be further improved, especially in melt processing, if they can be manufactured without the use of any organic solvent (Skaff et al., 2008). The Polypropylene—montmorillonite composites were... 

Montmorillonite, silicate, aluminosilicate, titanosilicate, calcium phosphate, zirconium phosphate, metal oxides, and heteropolyacids composites with Nation exhibit in general a modest barrier effect to methanol permeation (F, > 0.1), with a couple of exceptions aCloisite lOA composite [62] with 0.013 < F, < 0.065, and a chitosan-functionalized montmorillonite composite [71] with 0.028 < F < 0.050, in both cases for clay contents between 1 and 10 wt%. 

Rhee CH, Kim HK, Chang H, Lee JS (2005) Nafion/sulfonated montmorillonite composite a new concept electrolyte membrane for direct methanol fuel cells. Chem Mater 17 1691-1697... 

Mixture surface plot of tensile modulus and of the polypropylene organically modified montmorillonite composites as a function of mixture components. (Reproduced from Mittal, V., /. Thermoplast. Compos. Mater., 21, 9, 2008a. With permission from Sage Publishers.)... 

Wang, B.B., Song, L., Hong, N.N., Tai, Q.L., Lu, H.D., Hu, Y. Effect of election beam irradiation on the mechanical and thermal properties of intumiscent flame retarded ethylene-vinyl acetate copolymer/orcanically modified montmorillonite compositions. Radiat. Phys. Chem. 80, 1275-1281 (2011)... 

Zheng, H., Zhang, Y., Peng, Z., Zhang, Y.J. Inlluence of the clay modification and compatibilizer on the structure and mechanical properties of ethylene-propylene-diene rubber/montmorillonite composites. J. Appl. Polym. Sci. 92, 638-646 (2004)... 

Electrical conductivity measurements have been reported on a wide range of polymers including carbon nanofibre reinforced HOPE [52], carbon black filled LDPE-ethylene methyl acrylate composites [28], carbon black filled HDPE [53], carbon black reinforced PP [27], talc filled PP [54], copper particle modified epoxy resins [55], epoxy and epoxy-haematite nanorod composites [56], polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) blends [57], polyacrylonitrile based carbon fibre/PC composites [58], PC/MnCli composite films [59], titanocene polyester derivatives of terephthalic acid [60], lithium trifluoromethane sulfonamide doped PS-block-polyethylene oxide (PEO) copolymers [61], boron containing PVA derived ceramic organic semiconductors [62], sodium lanthanum tetrafluoride complexed with PEO [63], PC, acrylonitrile butadiene [64], blends of polyethylene dioxythiophene/ polystyrene sulfonate, PVC and PEO [65], EVA copolymer/carbon fibre conductive composites [66], carbon nanofibre modified thermotropic liquid crystalline polymers [67], PPY [68], PPY/PP/montmorillonite composites [69], carbon fibre reinforced PDMS-PPY composites [29], PANI [70], epoxy resin/PANI dodecylbenzene sulfonic acid blends [71], PANI/PA 6,6 composites [72], carbon fibre EVA composites [66], HDPE carbon fibre nanocomposites [52] and PPS [73]. 

Many other types of ECP have been described. These include PS-block-PPO [61], boron containing PVA [62], polyethylene dioxythiophene/polystyrene sulfonate [65], PC-ABS composites [64], PEO composites [64], PEO complexes with sodium lanthanum tetrafluoride [63], chlorine substituted PANI [70], PVP-PVA coupled with potassium bromate [57], PANI-PA 6,6 composite films [72], talc-PPY composites [54], epoxy resin alpha-haematite nanorod composites [56], PP-montmorillonite composites [69], magnetite containing polymers [105], LDPE [27], PC-acrylonitrile-butadiene composites [106], sodium ion conducting PEO complexed with sodium lanthanum tetrafluoride [63], PVDE [107], PANI composites [108], PP novolac resins [109], dendrimers containing light switchable azobenzene [110],PVP/PVA [107] and PPY[111]. 

Fig. 9 Bright field TEM images of nylon-6/ montmorillonite composite nanofibers from (a) pure HFIP solution and (b) a solution of 95% HFIP and 5% DMF (a single sheet, b stacked sheets/tactoids). Reprinted with permission from [87], Copyright (2002) Elsevier...

Li L, Bellan LM, Craighead HG, Frey MW (2006) Formation and properties of nylon-6 and nylon-6/montmorillonite composite nanofibers. Polymer 47 6208-6217... 

Stribeck N et al (2014) Studying nanostructure gradients in injection-molded polypropylene/ montmorillonite composites by microbeam small-angle X-ray scattering. Sci Tech Adv Mater 15(1) 015004... 

Figure 8. Microstructure of swelled soil of montmorillonite composition (a) fragment of hydromica clay microstructure before (b) and after (c) swelling.

Electrical properties have been reported on numerous carbon fiber-reinforced polymers, including carbon nanoflber-modified thermotropic liquid crystalline polymers [53], low-density polyethylene [54], ethylene vinyl acetate [55], wire coating varnishes [56], polydimethyl siloxane polypyrrole composites [50], polyacrylonitrile [59], polycarbonate [58], polyacrylonitrile-polycarbonate composites [58], modified chrome polymers [59], lithium trifluoromethane sulfonamide-doped polystyrene-block copolymer [60], boron-containing polyvinyl alcohols [71], lanthanum tetrafluoride complexed ethylene oxide [151, 72, 73], polycarbonate-acrylonitrile diene [44], polyethylene deoxythiophe-nel, blends of polystyrene sulfonate, polyvinyl chloride and polyethylene oxide [43], poly-pyrrole [61], polypyrrole-polypropylene-montmorillonite composites [62], polydimethyl siloxane-polypyrrole composites [63], polyaniline [46], epoxy resin-polyaniline dodecyl benzene sulfonic acid blends [64], and polyaniline-polyamide 6 composites [49]. 

Rhim et al. [116] reported that the water vapor permeability of PLA/Cloisite 20A (organically modified montmorillonite) composite films decreased significantly with increasing Cloisite 20A content (1.8 x 10 kgm/(m sPa) for Opph (part clay per 100 parts PLA)) to approximately 0.5 X 10 " kgm/(m sPa) for 15pph. Cussler et al. [126] developed and verified theories predicting the properties of barrier membranes to O2, water, and other solutes. Membranes that contained impermeable flakes or lamellae showed much lower permeabilities than conventional membranes. The variation of permeability depended on the concentration and aspect ratio of the flakes. 

Cao, D. and Heimann, R.B. (1993) Structure and mechanical properties of superabsorbent poly(acrylamide)-montmorillonite composite hydrogels. Polym. Gels Networks, 1, 225-246. 

An important result of having exfoliated montmorillonite composites in plastics is the increase in modulus, or stiffness of the material. Because the stiffness of the montmorillonite plates remains substantially constant on heating the composite, the relative stiffening effect increases as the polymer softens above its glass transition temperature. 

H. L. Qin, Z. G. Zhang, M. Feng, F. L. Gong, S. M. Zhang, and M. S. Yang, The influence of interlayer cations on the photo-oxidative degradation of polyethylene/ montmorillonite composites. Journal of Polymer Science Part B Polymer Physics, 42 (2004), 3006-12. 

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