Polyethylene/clay mixing

Solution blending Polar as well as nonpolar solvents can be used in this method. The polymer is solubilized in a proper solvent and then mixed with the filler dispersion. In solution, the chains are well separated and easily enter the galleries or the layers of the fillers. After the clay gets dispersed and exfoliated, the solvent is evaporated usually under vacuum. High-density polyethylene [24], polyimide (PI) [25], and nematic hquid crystal [26] polymers have been synthesized by this method. The schematic presentation is given in Scheme 2.2. 

The effect of the components and conditions of preparation on the properties of a 70/30 LDPE/clay composite is shown in Table I. The 10/90 mixture of LDEE Bakelite Polyethylene Resin DYNH-1 (Union Carbide Corp.) and Hydrite 10 clay (Georgia Kaolin Co.) was compounded at 150 C in the Brabender Plasticorder in the presence of MAH and/or t-butyl perbenzoate (tBPB). The EE-coated clay was then mixed with additional DYNH-1 LDPE at 130°C to yield a 70/30 PE/clay composite. A 30 70 PE/clay concentrate was prepared in a similar manner at 150 C and converted to a 70/30 EE/ clay composite at 130 C. The 10/90 PE/clay concentrate is an easily handled, clay-like product while the 30/70 concentrate is... 

A recent study on electrokinetic removal of ethyl benzene from contaminated clay showed a promising use of anionic-nonionic mixed surfactants. Surfactant addition resulted in 1.6-2.4-fold more removal than afforded by EK alone, and a mixed surfactant system, including 0.5% SDS and 2.0% PANNOX 110 (nonyl phenol polyethylene glycol ether) permitted optimal ethyl benzene removal (98%). This indicated that, in the presence of mixed surfactant micelles, the zeta potential of the soil particles significantly increased compared with that seen when anionic surfactant micelles were formed, and electrolytic mobility was thus enhanced (Yuan and Weng, 2004). The use of anionic-nonionic mixed surfactants in EK will also improve the desorption and migration of PAHs. 

The carbon paste electrodes were constructed from spectroscopic graphite (particle size <0.45 mm), which was mixed with nujol at a concentration of 1 g/ml and the necasary amount of moist clay to obtain a mass proportion of 10 %. This mixture was placed in a polyethylene tube with a geometric surface area of 1.6 mm. The connection was made with copper wire. 

Recently, Moad et al. [288,289] designed and prepared novel copolymer intercalant/dis-persant/exfoliant systems that are effective with unmodified clays at low levels (<20% with respect to clay), can be combined with commercial PP and clay in a conventional melt-mixing process, and do not require the use of additional compatibilizers. PP-clay nanocomposites prepared by direct melt mixing using unmodified MMX clays and a copolymer additive added at a level of only 1 wt.% with respect to PP for 5wt.% clay Authors investigated the following two classes of dispersants (1) polyethylene oxide-based nonionic surfactants... 

A very intriguing development concerns a drug delivery system for the treatment of periodontitis. It consists of two components. The first is a clay product loaded with tetracycline. The clay product is coated with chitosan to retard drug release. The second component is a thermo-responsive polymer mixed with polyethylene glycol that is syringable at room temperature but solidifies upon warming up to body temperature. The solidified polymer remains 60 min in situ. After that time, it still inhibits the formation of bacterial colonies, and still contains much more of the antibiotic than the control containing no chitosan. 

Silicate clays as recovered from nature do not lead to the formation of nanocomposites by simply physically mixing them with a polymer. Except with few hydrophilic polymers like polyethylene oxide [49-52] or polyvinyl alcohol [53,54], which have good interaction with the inorganic, highly hydrophilic, layered silicates, the surfaces of the silicates have... 

TEM photomicrographs of 80/20 wt/wt melt-mixed PCL/PEO blends with 1 wt% (A), 2 wt% (B), and 5 wt% (C), of cloisite Na+. (From L. Wang, Localization of Silicates Clay in Poly a-caprolactone (PCL), Polyethylene Oxide (PEO) Immiscible Polymer Blends, master s thesis, KathoUeke Universiteit Leuven, Belgium, 2003, under the supervision of G. Groeninckx, C. Harrats, andN. Moussaif.)... 

Even though this technique has been mostly used with water-soluble polymers, such as PEO, polyvinyl ether (PVE), polyvinylpyrrolidone (PVP), and poly(acrylic acid) (PAA) [134-141], intercalation from nonaqueous solutions has also been reported [142-145]. For example, high-density polyethylene (HDPE)-based nanocomposites have been prepared by dissolving HDPE in a mixture of xylene and benzonitrile with dispersed organomodified layered silicates (OMLSs). The nanocomposite was then recovered by precipitation from tetrahydrofuran (THE) [143], Polystyrene (PS)/OMLS-exfoliated nanocomposites have also been prepared by the solution intercalation technique, by mixing pure PS and organophilic clay with adsorbed cetyl pyrid-ium chloride [146]. Similarly, several studies have focused on the preparation of polylactide (PLA)-layered silicate nanocomposites using intercalation from solution. 

The influence of the inclusion size, shape, and surface treatment on the gas permeability of polyethylene in its micro- and nanocomposites has been investigated in various papers.Kato et al. report the N2 permeability of nanocomposites based on polyethylene (PE) melt compounded with maleic anhydride grafted polyethylene (MA-g-PE) and octadecylamine (C18-MMT) modified montmorillonite. The gas permeability coefficient for all the prepared samples are reported in Fig. 11.8. Interestingly, polyethylene, maleic anhydride grafted polyethylene, a 70/30 blend of PE/MA-g-PE and a blend of PE/MA-g-PE/MMT have almost the same permeability coefficient. Only the composites obtained by mixing the polymeric matrices with the modified montmorillonite show for PE/MA-g-PE/C18-MMT (PECHl) a decrement of 30% in permeability and for MA-g-PE/C18-MMT (PECH3) a decrement of 35%. The differences in the gas barrier property were attributed to the different dispersion of the clay silicate layers in the matrix. 

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