Organo clay mineral-melted polyolefin nanocomposites - Effect of surfactant/CEC ratio

Clay mineral-polymer nanocomposites are prepared by dispersing solid organo clay minerals in two different melted polyolefin matrices, namely polyethylene (PE) and ethylene vinyl acetate (EVA). The organo clay minerals are prepared by adding different amounts of surfactant corresponding to the CEC of the pristine clay mineral. The characteristics of the organo clay minerals are obtained by XRD, IR spectroscopy, TGA, and swelling volume measurements. The amount of added surfactant has a direct effect on the interlayer separation and organophilicity-hydrophilicity balance of the clay mineral, evidencing a particular behavior transition about OMt1.2 The intercalation of PE is found to be dependent on the interlayer distance of the organo clay minerals while EVA intercalates in the organo clay minerals whatever the amount of surfactant (> 0.5CEC), leading to the same interlayer spacing (4 DID). The polymer intercalation is more homogeneous in clay minerals having high surfactant loading corresponding to 1.5 and 2 CEC. Cone calorimeter results of the studied nanocomposites show a PHRR reduction of 32% for PE-OMt1.5 and of 47% for EVA-OMt1. For both polymers, the best compromise between mechanical and thermal properties, is obtained for organoclay filler obtained with an amount of added surfactant in a range 1-1.5 CEC. (c) 2006 Elsevier Ltd. All rights reserved.