Crystallization behavior and optical properties and mechanical properties of isotactic polypropylene nucleated with rosin-based nucleating agents

BACKGROUND: Rosin-based nucleating agents, as natural products, do not have any toxicity; hence they could be used in the industrial processing of polypropylene for the manufacture of food containers. As a result they have been the subject of considerable scientific interest in the literature. In this paper, the non-isothermal crystallization behavior, and optical and mechanical properties of isotactic polypropylene (iPP) nucleated with rosin-based nucleating agents are reported. Polarized optical microscopy, scanning electron microscopy and wide-angle X-ray diffraction were used to investigate the morphology and crystal structure of iPP with different rosin-based nucleators. The effects of a 1:1:1 co-crystal on the properties of iPP were also investigated. RESULTS: The addition of rosin-based nucleating agents led to the following changes in properties: (a) shortened crystallization half time, (b) decreased size of iPP crystals, (c) slightly increased crystallinity and (d) increased transparency, gloss, flexural modulus and tensile strength. The shrinkage of nucleated iPPs was similar to that of the blank iPP. CONCLUSION: Rosin-based nucleating agents in iPP were shown to be effective for nucleating crystals, reducing their size and causing preferential growth along the b-axis, but suppressing detectable spherulites. The 1:1:1 co-crystal was effective at 0.2 wt%, a greater concentration giving little additional improvement. (C) 2007 Society of Chemical Industry.