Production of modified clays and their use in polypropylene-based nanocomposites

The use of modified bentonite as a reinforcement in polypropylene (PP)/organoclay/maleic anhydride grafted polypropylene (MAPP) nanocomposites was investigated. The modified bentonites (organoclays) were prepared from raw (unpurified) bentonite (RB) and two quaternary ammonium salts with long alkyl tails: hexadecyl trimethyl ammonium bromide [HDA][Br] and tetrakisdecyl ammonium bromide [TKA][Br]. The ternary composites were produced by using a corotating twin screw extruder, followed by injection molding, and they exhibited microcomposite structure as observed by XRD. In order to observe the effects of purification of the bentonite, purified bentonite (PB) was obtained through sedimentation of raw bentonite, and later modified with two quaternary ammonium salts: dimethyl dioctadecylammonium chloride [DMDA][Cl] and [TKA][Br], and one quaternary phosphonium salt: tributyl hexadecyl phosphonium bromide [TBHP][Br]. Ternary nanocomposites (PP/organoclay/MAPP) with these organoclays were produced by using a corotating twin screw extruder, followed by batch mixing in an intensive batch mixer, and by injection molding. The use of [DMDA][Cl] and [TBHP][Br] resulted in nanocomposite formation, whereas the use of [TKA][Br] resulted in microcomposite formation as observed by XRD and TEM. Young's modulus of PP was increased by 30% with DMDA and 9% with TBHP. The yield strength of PP was increased by 15% with DMDA and 8.3% with TBHP. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013