Exfoliation copolymers

Su, S., Jiang, D. D., and Wilkie, C. A. Novel polymerically-modified clays permit the preparation of intercalated and exfoliated nanocomposites of styrene and its copolymers by melt blending, Polym. Degrad. Stab. (2004), 83, 333-346. 

John s pH 5.5 Daily Exfoliating Body Wash (U.K., South Africa) Johnson Johnson Hydrogenated jojoba oil, sodium/styrene/acrylate copolymer, acrylates/C10-C30 alkylacrylate cross-polymer... 

Nanocomposites with EPDM have been compatibilized with EPDM-MA. The viscoelastic data resembled those observed for the styrene copolymers small changes in Tg and modulus [Li et al., 2004]. However, the effect of MMT-ODA on depended strongly on T In CPNC with 5 wt% organoclay at -100 °C, , while at 25°C it reaches a maximum value of 2.6, compared with Er= 1.4 at this temperature. According to x-ray diffraction and transmission electron microscopy the CPNC was exfoliated and dispersed uniformly. 

A surfactant-free method for the preparation of exfoliated EVA/silicate nanocomposites has been developed recently by Sogah et al. [90,91]. The process comprises two steps the first step involves the reactive solution blending of MMT-Na+ (with a CEC 0.90 mequiv. g ) with preformed random copolymers of VA and 2-(acryloyloxy)ethyltrimethyl ammonium chloride (AETMC) the second step, also made by solution blending, consists of a dilution with EVA of the masterbatch prepared in the first step. As AETMC is more reactive than... 

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... 

Moad, G., Dean, K., Edmond, L., Kukaleva, N., Li, G., Mayadunne, R. T. A., Rfaender, R., Schneider, A., Simon, G., and Wermter, H. 2006. Novel copolymers as dispersants/intercal-ants/exfoliants for pol)q)ropylene-clay nanocomposites. Macromolecular Symposia 233 170-179. 

A viable process for manufacturing polyolefin-clay nanocomposifes by in situ polymerization requires adequate catalytic activity, desirable polymer microstructure, and physical properties including processibility, a high level of clay exfoliation fhaf remains stable under processing conditions and, preferably, inexpensive catalysf components. The work described in the previous two sections focused on achieving in situ polymerization with clay-supported transition metal complexes, and there was less emphasis on optimization of polymer properties and/or clay dispersion. Since 2000, many more comprehensive studies have been undertaken that attempt to characterize and optimize the entire system, from the supported catalyst to the nanocomposite material. The remainder of this chapter covers work published in the past decade on clay-polyolefin nanocomposites of ethylene and propylene homopolymers, as well as their copolymers, made by in situ polymerization. The emphasis is on the catalyst compositions and catalyst-clay interactions that determine the success of one-step methods to synthesize polyolefins with enhanced physical properties. 

Two approaches to tandem formation of copolymer nanocomposites (a) immobilization of the oligomerization catalyst, resulting in expansion of the clay layers during formation of a-olefins and (b) immobilization of the copolymerization catalyst, resulting in exfoliation of the clay by migration of the a-olefins into the interlayer spaces. 

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