Modification of layered silicates and layered double hydroxides for preparation of polyolefin nanocomposites

Abstract

In this desertion, two types of layered inorganic clays: layered silicate and layered double hydroxide (LDH) were chosen as nanofillers for the preparation of polyolefins nanocomposites. Both types of nanocomposites were prepared by melt intercalation technique using a twin screw extruder. The polyolefins grafted maleic anhydride (i.e PP-g-MAH and PE-g-MAH) were used as the compatibilizer. For polypropylene/layered silicate nanocomposites, the clay was modified with various cationic surfactants to obtain the organoclay. The nanocomposites prepared from organoclay that modified by the longer alkyl chain length surfactant, showed a good property. Two distinct groups of the nanocomposites, from a quasi-exfoliated to an intercalated morphology, were identified. The intercalated/flocculated morphologies were obtained when the organoclay content beyond 3 wt%. The different degrees of exfoliation/intercalation revealed the variable increase in thermal stability of the nanocomposites. The increase in glass transition termperature was related to the confinement effect between the polymer chains and the clay layers. For low density polyethylene/layered double hydroxide (LDH) nanocomposites, the LDH-clay was modified by various anionic surfactants. The result revealed that the size of the anionic surfactants played a vital role for the difference in morphological and thermal property. The obtained nanocomposites established partially exfoliated/intercalated mixed morphology and were preferable when the number of alkyl chain length was larger (n≥12). Incorporation of the organoclay enhanced both thermal and dynamic mechanical properties (i.e. storage modulus and glass transition temperature).