Polymer Processing Society edition:25 location:Goa date:1-5
Industrially produced polymers invariably contain an additive package, including for instance fillers, and are subjected to a complex thermomechanical history during production. Both flow and fillers influence the crystallization of semi-crystalline polymers. Nano-sized fillers in particular attract a lot of interest nowadays. In this project the effect of micro- to nano-sized fillers on flow-induced crystallization is probed using mixtures of polypropylene and zinc oxide with diameters between 1µm and 35nm. A significant nucleating ability, different for the different sizes, was observed using a broad variety of techniques. In order to capture the crystallization kinetics at processing speeds, a special sliding-plate flow-cell has been used which can attain speeds up to 1000 . It is observed that as the shear rate prior to crystallization is increased, the crystallization kinetics of the filled materials becomes similar, independent of filler diameter. This suggests that at high speeds, the crystallization is dominated by molecular orientation rather than by heterogeneous nucleation.