Grafting Clays

In our study, interesting results were obtained for membrane distillation experiments conducted using MF modified day membrane, validating the ability of these modified ceramic membranes to act as membrane contactors for desalination. An important influence of the feed temperature and NaCl concentration on the permeate flux was observed. In the same time, high salt rejection rates were obtained in AGMD process with grafted clay ceramic membranes. 

Figure 2.5 also shows an interesting finding in the case of trioctadecyl-methylammonium-grafted clay platelets. The order-disorder transition of these brushes was observed to be near 50°C. The same order-disorder... 

PP is probably the most thoroughly investigated system in the nanocomposite field next to nylon [127-132]. In most of the cases isotactic/syndiotactic-PP-based nanocomposites have been prepared with various clays using maleic anhydride as the compatibilizer. Sometimes maleic anhydride-grafted PP has also been used [127]. Nanocomposites have shown dramatic improvement over the pristine polymer in mechanical, rheological, thermal, and barrier properties [132-138]. Crystallization [139,140], thermodynamic behavior, and kinetic study [141] have also been done. 

Nylon blends, dyeing, 9 204 Nylon block copolymer, 19 762 Nylon carpet fibers, stain-resistant, 19 764 Nylon-clay nanocomposites, 11 313-314 Nylon extrusion, temperatures for, 19 789t Nylon feed yarns, spin-oriented, 19 752 Nylon fiber(s), 24 61 production of, 19 740 world production of, 19 7654 Nylon fiber surfaces, grafting of polymers on, 19 763-764... 

Polymer-Filler Composites thru In Situ Graft Copolymerization Polyethylene-Clay Composites... 

In the present paper, we report on the compatibilization of clay with polyolefins, specifically low and high density poly-ethylenes (LDPE, HDPE), through the radical-induced polymerization of maleic anhydride (MAH) in the presence of the polymer and clay, so that the MAH is grafted on the PE and the anhydride groups concurrently react with the filler surface (l, 2). 

During the last 5 years, there have been several reports of multiblock copolymer brushes by the grafting-from method. The most common substrates are gold and silicon oxide layers but there have been reports of diblock brush formation on clay surfaces [37] and silicon-hydride surfaces [38]. Most of the newer reports have utilized ATRP [34,38-43] but there have been a couple of reports that utilized anionic polymerization [44, 45]. Zhao and co-workers [21,22] have used a combination of ATRP and nitroxide-mediated polymerization to prepare mixed poly(methyl methacrylate) (PMMA)Zpolystyrene (PS) brushes from a difunctional initiator. These Y-shaped brushes could be considered block copolymers that are surface immobilized at the block junction. 

Among the two ionic polymerization techniques mentioned above, a living anionic polymerization should show the best possible control of polymer architecture and composition. Mono dispersed homopolymers, complex-block, graft, star, and miktoarm architectures have been accessible primarily by anionic polymerization methods [22]. They have been used to grow polymer brushes from various small particles such as silica gels graphite,carbon black, and flat surfaces [23-26]. Recent results have been reported on living anionic polymerizations on clay [27] and silica nanoparticles [28,29]. 

In the case of LASIP with clay nanoparticles, polystyrene was grafted using a DPE coinitiator. The montmorillonite clay surface and intergallery interfaces were intercalated with 1,1-diphenylethylene (DPE) modified to be an organic cation as shown in Fig. 4. Its intercalation was confirmed by a series of characterization methods including X-ray diffraction (XRD), FT-IR spectroscopy, TGA, and XPS. The results showed a complete replacement of... 

Even so, it is clear that certain structural features and special entities do influence catalysis by mineral surfaces, as well. The most common means by which they operate fall into four general classes, three of which have been extensively investigated. Covalent linkages in clays are less common than the others, being dependent on grafting to SiOH, which entities are not numerous in clays (10). 

Sodium bisulfite-china clay proved to be an efficient initiator for homopolymerization and graft polymerization of methyl methacrylate onto cellulose. Grafting reactions using ceric ammonium sulfate, sodium bisulfite-soda lime glass or -china clay are inhibited or retarded on adding soda lignin to the grafting medium. 

China clay having very nearly the empirical composition AI2O3.2Si02 2H2O (13) was used as soda lime glass with sodium bisulfite as an initiator system for grafting polymethyl methacrylate onto cellulose. 

Figure 1 shows a slight increase in the rate of grafting when using sodium bisulfite-china clay initiator system compared with sodium bisulfite-soda lime glass, while the increase in the rate of homopolymerization and the conversion % was distinct (Figure 2). 

For grafting polymethyl methacrylate onto lignocellulosic. substrates, sodium bisulfite may be used alone, i.e., in the absence of soda lime glass or china clay. It is worthy to mention that grafting onto pure celluloses failed to take place in absence of soda lime glass (9) (2) lignin already present in... 

PP is commercially modified by radical grafting with maleic anhydride to give maleated PPs used as compatibilizers for additives such as nanoclays. Similar strategies can be used to graft P-containing monomers to PPs. These copolymers, when blended with virgin PP, also allow com-patibilization with nanoclays but in addition work synergistically with the clays to improve flame retardance.51... 

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