Polyethylene/clay compatibilizers

With up to 40% clay, the compatibilized polymer/clay composites exhibit lower water vapor permeability than typical unfilled polyethylene. The compatibilized composites containing the clay particles were crosslinked, with the anhydride-grafted polyethylene bonded to the clay particles and uncrosslinked polyethylene. The composites exhibited improved flexural modulus, break strength, and notched Izod impact properties. 

Sanchez-Valdes S., Lopez-QuintanillaM. L., Ramirez-Vargas E., Medellin-Rodriguez F. J. and Gutierrez-Rodriguez J. M., Effect of ionomeric compatibilizer on clay dispersion in polyethylene/clay nanocomposites , Macromol Mater Eng, 2006, 291, 128-136. 

The performance of wood-polyethylene composites was found to improve by an appropriate compatibilization with different MAs and the additional incorporation of organo-clay particles [47] consisting of natural mont-morillonite modified with quaternary ammonium salt. The thermal expansion coefficient and the heat of deflection values indicated that these materials displayed an improved interfacial adhesion. 

Famulari A. et al. 2007. Clay-induced preferred orientation in polyethylene/compatibilized clay nanocomposites. Journal of Macromolecular Science, Part B Physics 46 355-371. 

In the last decade, considerable progress was observed in the field of PO/compatibil-izer (predominantly on the base of PO-g-MA)/organo-surface-modified clay nanocomposites. Polyethylene (PE), polypropylene (PP), and ethylene-propylene (EP) rubber are one of the most widely used POs as matrix polymers in the preparation of nanocomposites [3,4,6,30-52]. The PO silicate/silica (other clay minerals, metal oxides, carbon nanotubes, or other nanoparticles) nanocomposite and nanohybrid materials, prepared using intercalation/exfoliation of functionalized polymers in situ processing and reactive extrusion systems, have attracted the interest of many academic and industrial researchers because they frequently exhibit unexpected hybrid properties synergisti-cally derived from the two components [9,12,38-43]. One of most promising composite systems are nanocomposites based on organic polymers (thermoplastics and thermosets). 

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... 

Durmus, A., Woo, M., Kasgoz, A., Macosko, C. W., and Tsapatsis, M. 2007. Intercalated linear low density polyethylene LLDPE)/clay nanocomposites prepared with oxidized polyethylene as a new type compatibilizer Structural, mechanical and barrier properties. European Polymer Journal 43 3737-3749. 

R. Scaffaro, M. C. Mistretta, and F. P. La Mantia, Compatibilized polyamide 6/polyethylene blend-clay nanocomposites Effect of the degradation and stabilization of the clay modifier. Polymer Degradation and Stability, 93 (2008), 1267-74. 

Gaylord and coworkers recently presented evidence to show that the compatibilization of the low- and high-density polyethylene and kaolin or bentonite clays in the presence of MA involves both grafting and anhydride-hydroxyl reactions. The peroxide-catalyzed reactions were studied in a Brabender Plasticorder at 130-165°C. Presumably the in situ grafting and condensation reactions occurred as follows ... 

Nevertheless, in other cases, a plastidzing effect of the nanopartides has been reported, which leads to a decrease in both the values of Tg and the storage modulus. Artzi et al. [127] reported in EVOH-montmorillonite nanocomposites a decrease of Tg values from 5 wt% of day. The same authors predict two opposing effects on the transition the confined chain mobility owing to interaction buildup, and an increased mobility due to reduction in the crystallinity degree as a consequence of polymer-clay interaction [128]. The addition of a compatibilizer, either maleic anhydride-grafted ethylene-vinyl acetate (EVA-g-MA) or maleic anhydride-grafted linear low-density polyethylene (LLDPE-g-MA), led to a decrease in the Tg values [129]. This 5wt% day content maximum is also described by McAdam et cd. in PA6-day nanocomposites [130]. 

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