Structure and properties of PP/SBS/glass fiber hybrid composites. Part I: Crystallization behavior and morphology

The structure development, crystallization behavior and morphology were stu died in hybrid composites made with polypropylene/styrene-butadiene-styrene (PP/SBS) containing glass fibers (GF). The techniques applied include opti cal polarizing microscopy, X-ray diffraction and scanning electron microsco py (SEM). The isothermal crystallization studies of PP/SBS/GF revealed that SBS as well as CF could act: as good nucleating agents for PP. However, th e nucleation efficiency of GF is much higher than that of the SBS. At high concentrations of SBS (> 30%), the crystallization rate decreases even in t he presence of CF. This was attributed to the strong bonding between SBS an d glass, giving rise to an intermediate layer of SBS between PP and GF, whi ch was confirmed from the SEM of the fractured morphology of the injection molded hybrid composite. The orientation of GF was observed in the injectio n molded samples for certain compositions, and this was accompanied by an i ncrease of intensities of particular diffraction peaks in the XRD.