*Corresponding Author. E-mail: csha@pusan.ac.kr 179 Macromolecular Research, Vol. 14, No. 2, pp 179-186 (2006) Effect of a Compatibilizer on the Microstructure and Properties of Partially Biodegradable LDPE/Aliphatic Polyester/Organoclay Nanocomposites Kun-Jun Hwang, Jin-Woo Park, Il Kim, and Chang-Sik Ha* Department of Polymer Science and Engineering, Pusan National University, Busan 609-735, Korea Gue-Hyun Kim Applied Engineering Division, Dongseo University, Busan 617-716 , Korea Received October 17, 2005; Revised January 4, 2006 Abstract: In the present work, low density polyethylene (LDPE)/aliphatic polyester (APES)/organoclay ternary nanocomposites were prepared. In particular, the effect of a compatibilizer, polyethylene-graft-maleic anhydride (PE-g-MAH), on the morphology and properties of the ternary nanocomposites was investigated. LDPE/APES/ organoclay nanocomposites were prepared through melt intercalation method using two different kinds of organoclay. The dispersibility of silicate clays in the nanocomposites was investigated by X-ray diffraction and atomic force microscopy. The ternary nanocomposites showed higher tensile properties than the LDPE/APES blend did. The dispersibility and properties of nanocomposites containing Cloisite 30B were better than those of the nanocomposites containing Cloisite 20A. Unlike Cloisite 20A, hydroxyl groups in the intercalants in Cloisite 30B interlayer underwent a certain polar interaction with the carboxyl group of APES, favoring the intercalation of APES chains and the formation of LDPE/APES/Closite30B nanocomposites. However, the introduction of the polar hydroxyl groups also enhanced the interaction with the silicate surface at the same time, thereby rendering somewhat difficult the replacement of the surface contacts by LDPE chains, and impeding the extensive intercalation and further exfoliation of Cloisite 30B in the LDPE/APES matrix. The compatibilizer enhanced the intercalation of the polymer chain inside the clay gallery and thus improved the mechanical properties of the ternary nanocomposites. Rheological measurements of the nanocomposites via frequency sweep experiment indicated a certain interaction between the clay platelet and the polymer molecules in the melted state. Keywords: biodegradable, nanocomposite, compatibilizer, low density polyethylene, aliphatic polyester. Introduction Low-density polyethylene (LDPE) is one of the most widely used polymers and extensively used in packaging materials. Most light weight plastic packaging materials are disposed after one-time application. Plastic wastes have adverse effects on the environment. Legislative threats and increasing public concern about garbage crisis have gener- ated much interest in biodegradable packaging materials. Two different approaches for the production of biodegrad- able packaging materials are currently being studied: One is the development of completely biodegradable packaging materials. The other is the development of partially biode- gradable polymers obtained by blending non-biodegradable polymer and biodegradable polymers. In present technology, partially biodegradable polymers are more useful than com- pletely biodegradable ones because of the economic advan- tages and better properties. 1 For these reasons, there is an urgent need for the development for green polymeric mate- rials that would not involve the use of toxic components in their manufactures, and could allow degradation via a natural composting process. In this sense, polymer-layered silicate (PLS) nanocomposites based on biodegradable polymers were found to be very attractive due to the environmentally friendly nature of clay. So far reported biodegradable poly- mers for the preparation of nanocomposites are polylactide, poly(ε -caprolactone), and aliphatic polyester (APES), etc. However, there are very few works on the PLS based on polymer blends containing a biodegradable polymer as one component. Synthetic biodegradable APES, which are synthesized from diol and dicarboxylic acid through condensation poly- merization, are known to be completely biodegradable in soil and water and their properties are closely resembled to