Enhanced β‐crystal formation of isotactic polypropylene under the combined effects of acid‐corroded glass fiber and preshear

The acid‐corroded glass fiber (GF)/isotactic polypropylene (iPP) composite was injection molded by mixing–injection molding (MIM). Through this method, preshear can be imposed on melt during mix–plasticization process. The crystalline structure across the thickness direction of the injection‐molded bars was investigated by wide‐angle X‐ray diffraction and differential scanning calorimetry (DSC). It was unexpectedly found that, in core region, the acid‐corroded GF/iPP sample has the highest content of β‐form crystals, followed by uncorroded GF/iPP and neat iPP. Additionally, the crystalline morphology was investigated by polarized optical microscopy (POM) and scanning electron microscopy, and the results showed that β‐transcrystallization is preferably present in the acid‐corroded GF/iPP system. Confirmed by POM and DSC, the acid‐corroded GF shows strong β‐nucleation ability to iPP under static condition. Combined with the main features of MIM, three β‐nucleation origins in the acid‐corroded GF/iPP system under injection molding condition are proposed: (1) precursors induced by preshear in the barrel, (2) row‐nuclei induced by local shear, and (3) the acid‐corroded GF nuclei. POLYM. COMPOS. 34:1250–1260, 2013. © 2013 Society of Plastics Engineers