Cloisite clays

Intercalation of ammonium surfactant in the clay galleries increases its decomposition temperature [ 19-21 ] but, generally, the initial decomposition temperatures for commercially available organoclays are relatively low. For instance, the degradation temperatures of Cloisite clays, obtained by Cervantez-Uc et al. [17], are collected in Table 2.1. 

FR was greatly improved (Figure 10.1). As a result of the improved dispersion, only 5% Cloisite clay, together with 20% decabrome and 5% antimony trioxides, was needed to pass the UL-94 VO protocol with a sample 1.6 mm thick. Wang, Echols, and Wilkie reported that a concentration of more than 40% dibromostyrene in polypropylene was needed to achieve the same result in the absence of clay [16]. 

In contrast to the Cloisite clays, addition of phosphate-coated clays was able to improve the flame retardant response in certain classes of polymers. For example, addition of 5% RDP-coated clays to PC was able to achieve a UL-94 VI rating, whereas the addition of Cloisite 20A failed. Similarly, addition of 10% RDP-coated clays to HIPS achieved a rating of VI, whereas no effect was observed with Cloisite clays. 

Most engineered plastics mix with more than two polymers. It is hard to achieve flame retardant formulations because the microstructures of polymer blends are continuously changing during heating, which can result in phase separation. Even though the functionalized clays can be exfoliated and/or intercalated in homopolymers, it is necessary to consider the interfaces in polymer blends. Recently, Si et al. [5] showed that when Cloisite clays... 

Note Cloisite clay product by Southern Clay Products, Inc. 

Modification of well-ordered silicate materials such as MMT into more amorphous clay, for instance, the Cloisite clay, is crucial in order to improve the process-ability and performance of the polymer-inorganic materials. CloisitelSA possesses the largest basal spacing d spacing), that is, 31.5A as compared to the other commercial... 

Cloisite clay available in the market. Therefore, CloisitelSA is more flexible and, thus, can be fabricated according to the application commonly used in modifying the properties of the ionic polymers [42], Table 19.1 shows the characteristics of Cloisite clay as stated by Sonthern Clays Co. 

Maiti and Bhowmick reported exciting results that a polar matrix like fluoroelastomer (Viton B-50) was able to exfoliate unmodified clay (Cloisite NA ) as well as the modified one (Cloisite 20A) [93]. They studied morphology, mechanical, dynamic mechanical and swelling properties of fluoroelastomer nanocomposites. The unmodified-clay-filled systems showed better properties than the modified ones (Table 2.3). 

Figure 15.2 (A) XRD patterns of Cloisite Na (a). Thermoplastic starch TPS (b), and the TPS/Cloisite Na" hybrid (c). (Source Park et al., 2002). (B) TEM images of TPS/clay hybrids of different kinds of clay, (a) TPS95/Cloisite Na, (b) TPS95/Cloisite 6A, (c) TPS95/Cloisite 10A, (d) TPS95/Cloisite SOB. (Reproduced with kind permission from Park et al., 2002, Wiley-VCH Verlag GmbH Co. KGaA).

FIGURE 11.17 XRD patterns of two organoclays (Cloisite 10A, from Southern Clay Products, and VB166a) and two PSCNs with intercalated (PS/10A) or exfoliated (PS/VB16) morphology. 

Incorporation of modified clays into thermosetting resins, and particularly in epoxy35 or unsaturated polyester resins, in order to improve thermal stability or flame retardancy, has been reported.36 A thermogravimetric study of polyester-clay nanocomposites has shown that addition of nanoclays lowers the decomposition temperature and thermal stability of a standard resin up to 600°C. But, above this temperature, the trend is reversed in a region where a charring residue is formed. Char formation seems not as important as compared with other polymer-clay nanocomposite structures. Nazare et al.37 have studied the combination of APP and ammonium-modified MMT (Cloisite 10A, 15A, 25A, and 30B). The diluent used for polyester resin was methyl methacrylate (MMA). The... 

A series of five nanocomposite elastomer systems were prepared for this study incorporating 0, 1, 2, 4 and 8% (on total resin mass) of the organically modified montmorillonite clay Cloisite 6A. The appropriate level of Cloisite was dispersed in a starting resin blend of OH terminated PDMS (M -77,000 and Mn -550 g mol in a 3 1 ratio) by a combination of mechanical mixing and ultrasonic processing to give a nano-dispersion of clay platelets. The blend was subsequently crosslinked with a stoichiometric level of tetrapropoxysilane (TPOS) in the presence of 5% diphenylmethylsilanol (DPMS) chain terminator and 5% tin(II) 2-ethylhexanoate catalyst, cured in an open mould at 65°C for twenty minutes, then removed from the mould and post cured for a further fifteen hours at 65°C to give an elastomeric mat. 

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