VISCOELASTIC AND PLASTIC DEFORMATION BEHAVIOUR OF THERMOPLASTIC/CLAY NANOCOMPOSITES

摘要

A strong research effort is currently undertaken in the field of polymer matrix nanocomposites in which anisotropic clay platelets are dispersed in a thermoplastic. These materials usually display rather unique properties, even at low clay content, by comparison to more conventional polymer/filler systems. The case of Nylon 6/Clay hybrids is of particular interest since in-situ polymerization results in a Nylon matrix strongly bonded to the delaminated clay platelets. On the contrary, melt dispersion of organophilic clay in a non polar polymer such as polypropylene should in principle result in a reduced degree of grafting. Dynamic viscoelastic analysis is indicative of a noticeable difference when refering to the molecular dynamics of the glass transition. Plasticity results in which volume strain is recorded by video-extensometry show extensive cavitational behaviour while retaining a large strain at break above Tg of the matrix. This suggests in the case of PA6 that the usual shear banding plastic deformation mode is altered at least in its initiation step, due to the modification of the local chain dynamics by the level of polymer/mineral interactions.