Abstract
The dependence of impact properties on talc content and molecular weight (M) of polypropylene (PP) were investigated for talc-filled polypropylene (f-PP). The following results were obtained.
(1) For impact, a fracture mode transition from ductile to brittle exists, regardless of the presence of filler. The impact strength (IS) of PP increases rapidly with increasing temperatures above the ductile-brittle transition temperature (Tdb).
(2) The IS of PP depends strongly on molecular weight, but in f-PP, this dependence is decreased with increasing talc content at temperatures above Tdb.
(3) The Tdb of f-PP increases (-20→0°C) with increasing talc content (25→55wt%). The Tdb of PP is almost constant for the molecular weight range of 2.70×104∼6.71×104 despite the different flow properties (MFI=ca. 1∼26g/10min).
(4) The dependence of IS on talc content for f-PP at temperatures above Tdb is mainly controlled by fracture strain ε rather than fracture stress σ.
(5) Increasing the molecular weight of PP is an effective way to increase the impact strength IS. The use of talc filler shifts Tdb to higher temperatures. These results provide the basic concepts for material design for impact strength.
