Ammonium treated clays

Figure 15.6A Scanning electron micrographs (SEM) of fractured surfaces of (a) TPS-natural MMT nanocomposite containing 9.8 wt% clay, and (b) TPS-NH4MMT nanocomposite containing 10.7 wt% clay, (c) is the enlarged image for (b) showing spontaneously formed regular foam structures with 84% porosity in TPS-ammonium-treated clay.

Various workers have discussed the fire retardancy of polyvinylchloride (PVC) [55-59] using ammonium treated clay montmorillonite nanocomposites [52], hydroxyapatite nanocomposites [56] and antimony trioxide [57]. Lum [60] examined the effect of flame retardant additives on polymer pyrolysis reactions with a PVC composition containing 3 phr of SbiOs. It is well known that a synergistic flame retardancy effect is observed when SbiOs is incorporated into organic halide materials such as PVC. 

Figure 3.18 TGA curves for phosphonium- and ammonium-treated clay nanocomposites [44].

Thermal Decomposition of Organically Modified Layered Silicates The thermal stability of organically modified clays plays a key role in the synthesis and processing of polymer-layered silicate (PLS) nanocomposites. The thermal decomposition of ammonium-treated clays proceeds, schematically, in four steps ... 

In the literature, different commercial montmorillonites are used, especially for catalytic purposes (KSF or K10 montmorillonites). They are usually acid-treated clays, montmorillonite content of which is rather low. Our x-ray diffraction studies show 44% Ca-montmorillonite content of K10 montmorillonite, and 53% Na-montmorillonite content of KSF montmorillonite the CEC of KSF montmorillonite was found to be 30 meq/100 g by the ammonium acetate method (Richards 1957). A similar value has been given by Abollino et al. (2003). So, in a strict clay science sense, they cannot be considered as montmorillonite. Naturally, this causes no problems in organic chemistry when the main objective is the catalysis of a given reaction. 

Increased severity of acid treatment continuously increases the surface area and porosity of the clay, but cracking activity shows a maximum at intermediate treating severity (223,325). Mild acid treatment removes a large part of the alkali and alkaline-earth metals. More-severe acid treatment removes increasing quantities of aluminum and iron, as well as other metals still remaining after mild treatment. It has been reported that treatment of clay with ammonium chloride solution, instead of acid, also results in an active cracking catalyst (70). The ammonium ion displaces some of the metal constituents of the clay by base exchange the treated clay is then calcined to drive out ammonia. 

The effect of high shear mechanical mixing and soni-cation methods on the physical properties of the nanocomposites has been analyzed [84] using modified clays with a quaternary ammonium salt and calcium carbonate [85] and silane-treated clays [31]. Although the nanoclay is usually chemically modified to make it organophilic and compatible with the polymer matrix, untreated MMT was... 

Fig. 24 TEM micrographs of ternary epoxy, CTBN rubber and octadecyl ammonium-treated montmorillonite nanocomposites which were investigated with different polarity rubbers, (a) shows a broad view of the less polar rubber and the clay tactoids, clearly separated and (b) shows a close up of the more polar rubber close to silicate layers...

The incorporation of dimethyl-dialkyl ammonium treated montmoril-lonite clay does not alter the impact toughness in sub-zero temperatures, whereas the addition of nano-clay improves the strength at higher temperatures. However, the fracture toughness of nanocomposites and neat epoxy increases when they are treated with sea water for 180 days. The... 

Ray et al. [24] treated Cloisite 20A (montmorillonite modified with dimethyl-ditallow-containing approximately 65% Cig, 30% Cis, and 5% Ci4-ammonium cation chains) with a MAO solution, after vacuo-drying at 100 °C. The resulting MAO-treated clay was subsequently used for ethylene polymerizahon in the presence of a late transition metal catalyst (2,6-bis[l-(2,6-diisopropylphenylimino)ethyl] pyridine iron(ll) dichloride) and additional MAO in a glass reactor. They compared the result with homogeneous polymerization with the same catalyst in the presence of Cloisite 20A and observed that the supported catalyst was more efficiently exfoliated than when only a mixture of catalyst and clay was used. This comparison led them to conclude that at least some of the active centers resided within the clay galleries. Inductively coupled plasma (ICP) measurements showed that all MAO and catalyst remained in the solid catalyst after drying. 

Amine-treated clay Amine-treated lignite Aluminium sulphate Ammonium sulphite Barium sulphate (Barite)... 

On the other hand, clays modified with salts of aromatic amines, in which the N atom is directly linked to aromatic ring, exhibited higher thermal stability then those modified with alkylammonium compounds [117, 118]. The use of a combination of aromatic and aliphatic ammonium compounds was an effective strategy for synthesis of clays with sufficient thermal stability for thermoset polyimide resin (PI) [117]. In that case, the aromatic component of OLS provided higher thermal stability and the aliphatic component promoted intercalation. The benefits of combining aromatic and aliphatic surfactants to treat clay are also reported by other authors [ 119]. It was shown that clay treated with a 1 1 molar mixture of methylene dianihne (MDA) and dodecylamine resulted in an improvement in thermooxidative stability of Pl-based nanocomposites. 

The organic-inorganic hybrid materials have shown significant increases in properties compared to the conventional composites or neat polymers. The degree of dispersion of nanofiUers in a polymer matrix and the processing method play a key role on the final properties of the materials. Key objectives of researches are to design nanocomposites with enhanced properties at low filler contents. Different modified clays have been used in view of these objectives [31,52], There are reports on the use of ammonium-treated layered silicates [52,53], whereas the use of thermostable ILs such as pyridinium, imidazolium, or phosphonium is poorly reported. However, their combinations with poly(styrene) (PS) [54], PE [55], PP [56], poly(vinylidene fluoride) (PVDF) [57], and PET matrices [58] have been reported in the literature. 

Chen et al. [156] produced nanocomposite foams by melt processing TPS using urea as plasticizer and ammonium-treated montmoriUonite (NH MMT). They noticed that the use of urea also enhanced the dispersion of NH MMT in the TPS, making exfoHated TPS-clay nanocomposites possible. Synergistic effects of the urea plasticizer with ammonium treatment of the clay enhanced clay dispersion and foaming due to ammonia production. 

A study by Shah et on die moisture diffusion of a (non-epoxy) vinyl ester resin-based layered silicate nanocomposite also reported a deereased moisture diffiisivity of the nanocomposite, ascribed to the restricted mobility of the polymer chains tethered to the clay particles. A reverse effect, however, could be observed for the equilibrium water uptake of one of the two fillers investigated. The equilibrium water uptake of a vinyl-monomer containing clay nanocomposites increased from 0.012% (neat resin) to 0.021 (5% clay). The water uptake of the other, an alkyl ammonium-treated montmorillonite clay, Cloisite lOA, remained relatively unaffected by the filler addition. The increase of the first nanocomposites system was related to the strong, hydrophilic behaviour of the clay, which remains to some degree in the surface treated state. 

The first set of data is for oil production from 22 wells. A quaternary ammonium salt polymer clay stabilizer was utilized in five of the well treatments. Otherwise the 22 well treatment designs were identical. Use of the clay stabilizer in 5 well treatments resulted in a 131% production increase compared to a 156% increase after stimulation of 17 wells without clay stabilizer. Although the initial overall production response of the five clay stabilizer treated wells was less, the overall production decline rate was 4% per year compared to 16%/yr for the treatments which did not include the clay stabilizing polymer. This decline rate was determined for the period 4 to 24 months after well treatment. It is tempting to speculate that the lower initial production response of the five polymer treated wells was due to the formation of an adsorbed polymer layer which reduced formation permeability (particularly of the Wilcox Formation) significantly. 

Perhaps the most difficult ores to treat are the clay-containing carbonaceous sulphides. Significant progress has been made in treatment options for these ores. New sulphide activators (i.e. amine-treated CuSC>4, ammonium salts) and nitrogen gas flotation are amongst the new methods available. 

The presence of an organophilic clay increases the catalyst activity (10). Suitable clays include montmorillonite, hectorite, mica, etc. For example, Lucentite is a trioctylmonomethylammonium salt-treated synthetic hectorite. The clays are modified with quaternary ammonium compounds. The clays are heat treated prior to their use in the polymerization process. Further, the incorporated clay can improve the performance of the UHMWPE or function as filler. 

The part insoluble in ammonium acetate, containing the lead chromate, barium sulphate and clay, is suspended in 50 c.c. of water, treated with 25 c.c. of caustic potash solution (112 grams per litre) and heated to boiling for 10 minutes the lead chromate dissolves, whilst the barium sulphate and clay or kaolin remain undissolved and are collected, calcined and weighed. 

The pigment is treated with hydrochloric acid effervescence indicates copper or calcium carbonate any insoluble residue may contain barium sulphate, gypsum (in large quantity), lead sulphate or clay, which may be identified by the usual methods. The solution is treated with excess of ammonium carbonate if a precipitate forms, it is tested especially for alumina, lime and magnesia. 

A study33 has been made of the rearrangement of /V-triarylmethylanilines to their p-triarylmethyl derivatives. A-Methyl-A-nitrosoaniline has been observed to undergo a Fischer-Hepp rearrangement when treated with montmorillonite clay,34 and /V-aryl-A-nitrosohydroxylamine ammonium salts (30) have been transformed35 into azoxy... 

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