Polymorphism in Sheared Isotactic Polypropylene Containing Nucleant Particles

This study explored the combined influence of shear flow and nucleating agents on isotactic polypropylene (iPP) crystallisation. The study showed that oriented α‐iPP crystals were not necessary to form β‐iPP crystals, contrary to the accepted view that the surface of oriented α‐iPP crystals provides nucleation sites for an α‐iPP to β‐iPP growth transition. Instead it was proposed that flow‐induced mesomorphic point‐like nuclei preferentially nucleates β‐iPP. The combined effect of shear flow and nucleant was found to promote γ‐iPP crystals. The surprising γ‐iPP nucleation effect was explained by the high density of flow‐induced and heterogeneous nuclei present at the start of crystallisation. This paper investigated the combined influence of shear flow and nucleating agent on polypropylene crystallisation. The study showed that oriented α‐iPP crystals were not necessary to form β‐iPP crystals as previously thought. A combination of shear flow and nucleating agent yielded a surprising γ‐iPP nucleation effect. An updated model for polypropylene crystallisation is presented.