Effects of melt structure on crystallization behavior of isotactic polypropylene nucleated with α/β compounded nucleating agents |
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| Authors: | Qiyan Zhang Zhengfang Chen Bing Wang Jinyao Chen Feng Yang Jian Kang Ya Cao Ming Xiang Huilin Li |
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| Affiliation: | 1. State Key Laboratory of Polymer Materials Engineering, Chengdu, People's Republic of China;2. Polymer Research Institute of Sichuan University, Chengdu, People's Republic of China;3. College of Polymer Science & Engineering of Sichuan University, Chengdu, People's Republic of China |
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| Abstract: | In this study, the melt structure of isotactic polypropylene (iPP) nucleated with α/β compounded nucleating agents (α/β‐CNA, composed of the α‐NA of 0.15 wt % Millad 3988 and the β‐NA of 0.05 wt % WBG‐II) was tuned by changing the fusion temperature Tf. In this way, the role of melt structure on the crystallization behavior and polymorphic composition of iPP were investigated by differential scanning calorimetry (DSC), wide‐angle X‐ray scattering (WAXD) and scanning electron microscopy (SEM). The results showed that when Tf = 200°C (iPP was fully molten), the α/β‐CNA cannot encourage β‐phase crystallization since the nucleation efficiency (NE) of the α‐NA 3988 was obviously higher than that of the β‐NA WBG‐II. Surprisingly, when Tf was in 179–167°C, an amount of ordered structures survived in the melt, resulting in significant increase of the proportion of β‐phase (achieving 74.9% at maximum), indicating that the ordered structures of iPP played determining role in β‐phase crystallization of iPP nucleated with the α/β‐CNA. Further investigation on iPP respectively nucleated with individual 3988 and WBG‐II showed that as Tf decreased from 200°C to 167°C, the crystallization peak temperature Tc of iPP/3988 stayed almost constant, while Tc of iPP/WBG‐II increased gradually when Tf < 189°C and became higher than that of iPP/3988 when Tf decreased to 179°C and lower, which can be used to explain the influence of ordered structure and α/β‐CNA on iPP crystallization. Using this method, the selection of α‐NA for α/β‐CNA can be greatly expanded even if the inherent NE of β‐NA is lower than that of the α‐NA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41355. |
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| Keywords: | crystallization morphology polyolefins thermal properties |
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