Nucleus density and crystallization behavior of isotactic polypropylene nucleated with different α/β compound nucleating agents

Different compound nucleating agents consisting of a highly efficient novel α-nucleating agent N,N’-bis(benzoyl) sebacic acid dihydrazide and three typical β-nucleating agents N,N-dicyclohexylterephthalamide, rare earth compound (WBG-II) and calcium pimelate were incorporated into isotactic polypropylene (iPP), and the isothermal crystallization behavior of iPP nucleated with these compound nucleating agents was investigated by differential scanning calorimetry. Based on the classical Avrami theory and the calorimetric curves under isothermal conditions, the crystallization half-time and the Avrami index can be calculated. The results demonstrate that addition of these nucleating agents reduced the crystallization half-time and speed up the crystallization process of iPP. In addition, the nucleus density of pure and nucleated iPP was further calculated from the Lamberti model and the results illustrate that the nucleus density of iPP after addition of different compound nucleating agents was increased greatly and it was several orders of magnitude higher than that of pure iPP.