Morphology and mechanical properties of transcrystalline isotactic polypropylene

Abstract

We examined mechanical and morphological properties of fully transcrystalline polypropylene grown from the surface of poly(tetrafluoroethylene) sheets. Comparison of mechanical properties between transcrystalline and spherulitic polypropylenes demonstrated that Young's modulus is dependent on the crystallinity and independent of the supermolecular structure. On the other hand, the mechanical yielding process was predominantly affected by the supermolecular structure, and the mechanical energy required for yielding of transcrystalline sheets was greater than that of the spherulitic morphology. In addition, it was found that mechanical necking is required for the alignment of lamellae in the stretching direction. This means that the unfolding process of lamellae orienting in the stretching direction is associated with necking and ductility.

Characterization of PP/TPV/MMT Ternary Nanocomposites Produced by Injection Molding

“…A distinctive feature is that massive craze evidences are seen in the region between the skin and the core (Figure ). In PP injected parts, craze mechanisms are generally not seen in the samples’ skin, but they can be seen in the shear region located between the skin and core layers . A plausible explanation is that the molecular orientation of skin increases the material resistance to undergo crazing, while columnar morphology, typical of the shear region, enhances the PP matrix ability to experiment crazing.…”

“…In PP injected parts, craze mechanisms are generally not seen in the samples’ skin, but they can be seen in the shear region located between the skin and core layers . A plausible explanation is that the molecular orientation of skin increases the material resistance to undergo crazing, while columnar morphology, typical of the shear region, enhances the PP matrix ability to experiment crazing. It was pointed out in literature that nanoclay is capable of promoting the development of this columnar structure and therefore enhances the ability to develop craze.…”

Relating microhardness to injection molding induced morphology: A study of microbeam synchrotron WAXD

“…Yield strength corresponded of the disruption of lamella continuity and a higher force is required for the disruption to the cross‐hatched structure because of higher density of active lamellar pulling points 27. A higher ratio of tangential lamellae increase yield energy, so the yielding process is basically governed by the superstructure 28. Therefore, crystallinity mainly affected to microhardness but superstructure like cross‐hatched lamellae which is induced biaxially in extended melt flow is also not neglected in the injection molded PP plaques.…”