Site-resolved X-ray investigations on injection-molded polypropylene filled with magnesium hydroxide

Plates were injection molded from isotactic polypropylene filled with up to 40 wt% Mg(OH)(2) and investigated by site-resolved wide-angle X-ray scattering measurements, performed directly on the plates or on cross-sections cut from the plates. The experimental data were analyzed in terms of various parameters and functions capable of characterizing the orientation of the filler particles and of the polypropylene crystallites in dependence on the distance from the gate and from the surface of the plates. The results establish that Mg(OH)(2) influences the orientation of the polypropylene crystallites only moderately, in spite of the pronounced orientation of the platy filler particles parallel to the mold surface, whereas other platy fillers like talc or graphite were found to exert a very pronounced orientation effect on the polypropylene matrix. The different efficiency of Mg(OH)(2) may be explained by the poor ability of this filler to nucleate polypropylene.