Viscosity of polymer composites with high content of metal powders processed by injection moulding
Lech Paszkowski, Dionizy Biało, Andrzej Skalski, Ryszard Pilawka
Quarterly No. 1, 2011 pages 55-60
DOI:
keywords: functional polymer composite, injection, viscosity, functional powder
abstract An important feature of injection-processed functional polymer composites is viscosity. Powder increases the viscosity of such a composite. Viscosity depends on the polymer processing properties and the shape and size of the powder particles. The injection temperature is also important. In the conducted analyses, High Impact Polystyrene (HIPS) and General Purpose Polystyrene (PS) served as the matrix for the composites. Powders with flaky and spherical particles constituted the functional phase. Powders with permanent magnetic characteristics produced from Nd-Fe-B alloys were used. In the analysis, multi-fractional (commercial) powders and selected fractions of two types of powders were used. Composites containing variable quantities of multi-fractional powders were obtained. The content of the powders was from 40 to 54% of flaky powder and up to 64% of spherical powder by volume. In addition, composites containing the selected fractions of both types of powders were prepared. The content of fractional powders was constant and it was 48% by volume. The samples were produced by injection of the composites at temperatures from 160 to 240°C. Polystyrenes and composites with a zero shear rate have the greatest viscosity. Increasing the shear rate leads to a reduction of viscosity. The viscosity of composites with flaky powder decreases at the fastest rate. For spherical powder, the viscosity reduction rate is slower and for polystyrenes - the slowest. Slightly higher viscosity values (for the same shear rates) were obtained for general purpose polystyrene and the composites in which it served as the matrix. In composites with flaky powder, the reduction in viscosity is greater if the powder content is higher. For composites with spherical powder, an increase of the shear rate results in constant reduction of their viscosity. The viscosity of composites (with a constant content of fractional powders) decreases along with an increase of the size of its particles. An attempt was also made to explain the phenomenon of the faster reduction of viscosity of composites with flaky powder compared to composites with spherical powder through proposing a model describing the emer-gence of easy-slip surface. In addition, as the temperatures of the injected composites increase, their viscosities decrease.