Montmorillonite layered silicates

Fig. 8-2 Structure of a 1 1 (kaolinite) and a (montmorillonite) layer-silicate clay mineral.

Thellen, C., Orroth, C., Froio, D., Ziegler, D., Lucciarini, J., Farrell, R., D Souza, N.A., Ann, J. Influence of montmorillonite layered silicate on plasticized poly(L-lactide) blown films. Polymer 46, 11716-11727 (2005)... 

Diddams, P.A. et al. 1984. Synthesis, Characterization and Catalytic Activity of Beidellite-Montmorillonite Layered Silicates and their Pillared Analogues. J. Chemical Society (A) Chemical Communications 1340-42. 

Sumita M, Tsukumo Y, Miyasaka K et al (1983) Tensile yield stress of polypropylene composites filled with ultrafine particles. J Mater Sci 18 1758—1764 Thellen C, Orroth C, Froio D et al (2005) Influence of montmorillonite layered silicate on plasticized poly(l-lactide) blown films. Polymer 46 1716-11727 Uyama H, Kuwabara M, Tsujimoto T et al (2003) Green nanocomposites from renewable resources plant oil-clay hybrid materials. Chem Mater 15 2492-2494 Wang SF, Shen L, Zhang WD et al (2005a) Preparation and mechanical properties of chitosan/ carhon nanotuhes composites. Biomactomolecules 6 3067—3072... 

Further indication of the importance of a proper dispersion of layered silicates in PNCs is provided by Ranade et al [21] in a study reporting a com-pai ison between the creep behavior of maleated and non-maleated polyethylene-montmorillonite layered silicate blown films. The authom claimed that maleated polyethylene (PE-g-MA) facilitated the dispersion of montmorillonite layered silicate in the polyethylene (PE) matrix. The creep experiments were perfonned at 25% and 50% of the yield stress and the resulting creep compliance was modeled with the Burgers model. The fitting parameters of the Burgei-s model for the creep behavior (evaluated at 50% of the yield stress) of neat PE matrix and relative PNCs are summarized in Table 9.2. 

Table 9.2. Parameters of the Burgers model fitting the creep behavior of polyethylene -montmorillonite layered silicate (MLS) rianocomposites compatibilized with PE grafted maleic anhydride. Short-term creep tests were performed up to 3 600 s at an applied stress of 50% of the yield stress [21]...

Ranade A, Nayak K, Fairbrother D and D Souza N A (2005) Maleated and non-maleated polyethylene-montmorillonite layered silicate blown films creep, dispersion and crystallinity. Polymer 46 7323-7333. 

The synthesis of palladium nanoparticles on montmorillonite layer silicates was studied. The Pd particles were prepared in situ in the interlamellar space of montmorillonite dispersed in an aqueous medium. Macromolecules were adsorbed on the support from an aqueous solution, followed by adsorption and reduction of Pd ions. The Pd° nanoparticles appear and grow in the internal, interlamellar space as well as on the external surfaces of the lamellae. Well-crystallized kaolinite clay can be disaggregated by the intercalation of DMSO to individual lamellae, which may serve as excellent supports for metal nanoparticles. After the adsorption of palladium precursor, metal nanocrystals were reduced by hydrazine or sodium borohydride between the kaolinite lamellae, i.e., in the interfacial layer acting as a nanoreactor. The incorporation of nanoparticles between the lamellae was shown hy XRD measinements. This procedure makes possible the steric control and restriction of nanoparticle growth. The stability of nanoparticles can be further enhanced hy the addition of polymers (PVP) and surfactants (alkyl-ammonium salts) that are also adsorbed between the kaolinite lamellae. The presence of the particles was also verified and their sizes were quantified by TEM measurements. 

Retort is a high temperature sterilization process that is used to prolong the shelf life of military rations. Ethylene co-vinyl alcohol (EVOH) /montmorillonite layered silicate (MLS) nanocomposites were co-extruded with retort grade polypropylene (PP) into a multilayer cast fdm to determine if the addition of MLS to EVOH improved barrier, mechanical, thermal and retort properties. The PP/EVOH-MLS/PP structure showed an improvement in some properties such as water vapor transmission rate. Young s modulus, and seal strength before retort in comparison to the PP/EVOH/PP structure however, the improvement in properties was lost after the retort process. 

Montmorillonite Layered Silicate (MLS) Southern Clay Cloisite 25A Nanoparticle... 

Montmorillonite (All,7Mgo.3)Si3.9Alo,lOlo(OH)2 2 1 layer-silicate... 

Why can layer silicates serve as models for replication processes The answer is simple they have properties which are observed in replicating systems. Montmorillonite crystals contain similar parallel layers, the distance between which... 

Smectites are 2 1 charged layered silicates from natural (montmorillonite, hectorite, beidellite, saponite etc.) or synthetic (synthetic fluorohectorites, such as... 

The most significant class of inorganic supports, which is used for the direct ion exchange of positively charged transition-metal complexes, are smectite clays. Pin-navaia has introduced the use of these swelling, layered silicate clays for catalysis. Other clays include montmorillonite, bentonite, and laponite. As shown by Pinna-vaia, cationic transition-metal complexes can be readily exchanged (intercalated) into the solvated interlayers of these silicates (Eq. (1)) [117] ... 

The authors [1] studied kinetics of poly (amic acid) (PAA) solid-state imidization both in the presence of nanofiller (layered silicate Na+-montmorillonite) and without it. It was found, that temperature imidization 1] raising in range 423-523 K and nanofiller contents Wc increase in range 0-7 phr result to essential imidization kinetics changes expressed by two aspects by essential increase of reaction rate (reaction rate constant of first order k increases about on two order) and by raising of conversion (imidization) limiting degree Q im from about 0,25 for imidization reaction without filler at 7 i=423 K up to 1,0 at Na -montmorillonite content 7... 

Sorption depends on Sorption Sites. The sorption of alkaline and earth-alkaline cations on expandable three layer clays - smectites (montmorillonites) - can usually be interpreted as stoichiometric exchange of interlayer ions. Heavy metals however are sorbed by surface complex formation to the OH-functional groups of the outer surface (the so-called broken bonds). The non-swellable three-layer silicates, micas such as illite, can usually not exchange their interlayer ions but the outside of these minerals and the weathered crystal edges ("frayed edges") participate in ion exchange reactions. 

This fact may explain the superiority of montmorillonite over vermiculite as an adsorbent for organocations (3, 4). Complicating this description, however, is the fact that a sample of any particular layer silicate can have layer charge properties which vary widely from one platelet to another (j>). By measuring the c-axis spacings, cation exchange capacity, water retention, and other properties of layer silicates, one obtains the "average" behavior of the mineral surfaces. 

However, when protonated TEMPAMINE adsorbs by cation exchange on fully hydrated layer silicate clays (10, 11), the spectrum becomes less symmetrical as shown in Figure 5. The beidellite and montmorillonite spectra have line shapes typical for nitroxide molecules with rotational frequencies on the order of 10 Hz (17). 

The most-popular nanofiller is a natural layered silicate, montmorillonite, that is subjected to specific treatments. The properties of the final nanocomposite depend on the these treatments and the mixing efficiency. 

Tennakoon DTB, Thomas JM, Tricker MJ, et al. 1974. Smface and intercalate chemistry of layered silicates. Part 1. General introduction and uptake of benzidine and related organic molecrtles by montmorillonite. J Chem Soc Dalton Trans 20 2207-2211. 

Phyllosilicates (clay minerals) - layered silicates such as Al4Si4O10(OH)8 (kaolinite) and (Ca,Na)o.7(Al,Mg,Fe)4(Si,Al)802o(OH)4.nH20 (montmorillonite, also called smectite). 

On the other hand, Bhattacharya et al. have reported the plasticization effect of organically modified layered silicates on dynamic mechanical properties [13]. In this work, nanocomposites of SBR have been prepared using various nanofillers like modified and unmodified montmorillonite, SP, hectorite etc. It has been observed that the Tg shifts to lower temperature in all the nanocomposites, except for systems from hectorite and NA. This is due to the fact that clay layers form capillaries parallel to each other as they become oriented in a particular direction. Due to wall slippage of the unattached polymer through these capillaries, the Tg is lowered, which could be even more in the absence of organo-modifiers [13]. A similar type of plasticization effect is also noted in the case of the low... 

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