Synthetic clay laponite

Name(s) Hydrous sodium lithium magnesium silicate CAS m 53320-86-8 

Chemical formula Na,° [Si8Mg5 5Li, 4H4024] Chemical fhnctionality  

Moisture content, % 10 Water solubility, % insoluble pH of water suspension 9.8 

Particle shape layered silicate Crystal structure trioctahedral smectite  

Sieve analysis, residue on 325 mesh sieve 1-2% Specific surface area, m /g 310-380  

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The major elass of plate-like colloids is that of clay suspensions [21]. Many of these swell in water to give a stack of parallel, thin sheets, stabilized by eleetrieal eharges. Natural elays tend to be quite polydisperse. The synthetic clay laponite is comparatively well defined, eonsisting of dises of about 1 nm in thiekness and 25 nm in diameter. It has been used in a number of studies (e.g. [22]). 

Following this Hne, Negrete-Herrera et al. recently synthesized PLS nanocomposites based on a synthetic clay Laponite and a fihn-forming copolymer of styrene and butyl acrylate (polystyrene-co-butylacrylate) through emulsion polymerization. 

The first examples of cationic exchange of bis(oxazoline)-metal complexes used clays as supports [49,50]. Cu(II) complexes of ligands ent-6a, 6b, and 6c (Fig. 15) were supported on three different clays laponite (a synthetic clay), bentonite, and montmorillonite KIO. The influence of the copper salt from which the initial complexes were prepared, as well as that of the solvent used in the cationic exchange, was analyzed. 

Vaccari (1983,1999) has given a state-of-the-art account of the preparation and catalytic properties of cationic and anionic clays. Some examples of industrial importance have also been reported. Clays exhibit many desirable features, such as low cost, wide range of preparation variables, ease of set-up and wOrk-up, high selectivity, and environmental friendliness. Cationic clays are widespread in nature, whereas anionic clays are rarely found in nature, but they can be synthesized cheaply. Cationic clays are prepared from the minerals but industrial anionic clays are generally synthetic. Smectite clays exhibit both Brpnsted and Lewis acid sites on the edges of the crystals. Hammet s acidity function values are as follows Na -montmorillonite (M), -3 to t- 1.5 NH4VM -3 to 1.5 H M -8.2 to -5.6 acid activated clay less than -8.2. Laporte also has a synthetic version of cationic clays, Laponite. The acid... 

There are many other forms of clay including synthetic clays such as laponite, a synthetic hectorite. Suitable tuning of the properties of these systems can produce similar structures. These systems have the advantage of small particle size and a relatively improved level of particle monodispersity over their naturally occurring counterparts and are being increasingly used as rheology modifiers. 

Exchange of organic ammonium cations. Exchange selectivity of monovalent alkyl ammonium cations in montmorillonites (40-41) and octahedrally substituted synthetic clay minerals (laponite) increases with their chain length (42) and along the series... 

SCPX2231 Laponite synthetic clay now from Southern Clay Co. with 2M2HT... 

For instance, Herrera et al. recently conducted a series of experiments on Laponite [280-283]. Laponite is a synthetic clay that is similar in structure to MMT, except for the nature of the interlayer cation (Mg + for Laponite and Al + for MMT) and the clay dimensions. Each elementary Laponite disk has a thickness of around 1 nm and a diameter of 30 0 nm. In addition, Laponite also has the advantage over natural clays of being chemically pure and free from external contaminations. All these properties make Laponite a valuable candidate for use in PCN synthesis. 

Laponite RD is a fnlly synthetic clay similar in structure and composition to natural hectorite of the smectite group (Scheme 1). Each layer is composed of three sheets two outer tetrahedral sihca sheets and a central octahedral magnesia sheet. Isomorphous substitution of magnesium with Uthium in the central sheet creates a net negative charge compensated by intralayer sodium ions located between adjacent layers in a stack. The cation exchange capacity of Laponite is 0.75 meq The dimen-... 

Whorlow (1992) published a book on rheological techniques that inctudes dynamic tests and wave propagation tests. In the appendix, he listed a number of rheologicat inves-tigahon equipment manufacturers. Some of the techniques appiy more to polymers and are not relevant to our discussion. Dynamic vibration tests have been extended to fresh concrete (Teixera et at., 1998). Concord and Tassin (1998) described a method to use rheo-ophcs for the study of thixotropy in synthetic clay suspensions. A rheometer optical analyzer was used on laponite, a synthetic hectorite clay. Laponite was mixed with water and tests were conducted at various intervals for up to 100 days. Rheo-ophcs seems to be... 

Natural clays are usually contaminated with other types of minerals. Therefore, it is of particular advantage to use synthetic clays. An easily obtainable synthetic clay is laponite, which is a lithium-magnesium silicate which forms extended sheaths. The laponite which is commercially available and can be obtained from Laporte Industries, is also easily synthesized in the laboratory. Due to its purity, laponite is a useful model system for studying clays. Their properties are by now fairly well known through several basic investigations (22, 23). 

Synthetic clays prepared in a reaction between Mg, Li, and Na-silicate salts (Laponite) were used by Shemper et al for examination of photopolymerization methyl hydroxyl methyl acrylate. It was found that the clay autoaccelerated the reaction. 

A sixth article on modulus performance of nylon 6-clay nanocomposites was also published in 1995 in the Journal of Applied Polymer Science [25] by Toyota Research. The Young s modulus of nylon 6-clay nanocomposites was prepared with montmorillonite, saponite, a synthetic hectorite (Laponite RD), and synthetic mica. The in situ polymerization procedure with 12-aminolauric acid exchanged onto the minerals was utilized to prepare the nylon 6 nanocomposites. The montmorillonite polymer nanocomposite has the largest modulus, followed by mica, saponite, and, the lowest value, Laponite RD. 

For the natural clay minerals in Table 9.1 (i.e., excluding Laponite which is a synthetic clay), the predominance of the clay samples with large 7 values (taken arbitrarily as 7 >2 mJ/m ) tend to be lithium-saturated clays followed in abundance by cesium-saturated clays. It has been known for some... 

Laponite, a synthetic hectorite clay, when suspended in water, forms disclike particles with a thickness of 1 nm, a diameter of about 25 nm, and a negative surface charge density stabilizing dispersions in water. Formation of a cross-linked polymer network using a small amount of Laponite indicates that these nanoparticles act as a multifunctional cross-linker with a large effective functionality (Okay and Oppermann 2007). 

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