Polypropylene–clay nanocomposites: Influence of low molecular weight polar additives on intercalation and exfoliation behavior

Abstract

AbstractThe influence of low molecular weight additives containing polar groups and modified polyolefin‐based compatibilizers on polypropylene (PP)‐clay nanocomposites (PPCN) has been studied, in terms of intercalation and degree of exfoliation achievable by melt‐state mixing processes. PPCN were prepared by melt mixing two PP homopolymers with organically‐modified montmorillonite type clay, in the presence of maleic anhydride‐grafted polypropylene (PP‐MA) compatibilizer. XRD analysis shows that interlayer spacing of clay has been increased dramatically, while TEM results show a significant improvement of clay dispersion in the PP matrix, when nanocomposites are prepared with commercial PP containing short‐chain organic additives with polar end groups. Subsequent studies based upon customized PP formulations, with amide‐type slip additive, confirm the intercalation of this additive into the clay galleries and its positive and significant impact on clay dispersion. Contact angle measurements suggest that these additives diffuse into the clay gallery space rather than migrating away from the bulk of the PPCN matrix. The interaction between polar group (NH2) of this additive and the polar sites on the filler surface appears to be the driving force for the intercalation. POLYM. ENG. SCI. 46:1008–1015, 2006. © 2006 Society of Plastics Engineers