Toward a Further Understanding of the Decreased β-Phase Content in β-Nucleated Polypropylene Random Copolymer: From Nucleation and Growth Kinetics
Toward a Further Understanding of the Decreased β-Phase Content in β-Nucleated Polypropylene Random Copolymer: From Nucleation and Growth Kinetics
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DOI：
10.1021/acsapm.3c01407
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发表时间：
2023-08
影响因子：
5
通讯作者：
Xuan Sha;Y. Yue;Wenan Tie;Xiaoyan Tian;Jiachun Feng
中科院分区：
文献类型：
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作者：
Xuan Sha;Y. Yue;Wenan Tie;Xiaoyan Tian;Jiachun Feng
与聚丙烯均聚物（PPH）相比，β-成核剂（β-NA）在插入共聚单体的聚丙烯无规共聚物（PPR）中诱导的β相较少。普遍的观点认为，共聚单体的插入导致β-相（kβ）的相对含量降低，这是PPR中β-相（kβ）的动力学生长不利的原因。为了进一步了解β在PPR中的减少，我们分别研究了以β-NA，N,N ' -二环己基对苯二甲酸（DCHT）成核的各种等规聚丙烯（ipp）的成核和生长行为。通过分馏结晶，计算出在PPR中加入乙烯后，DCHT形成β-核的可能性（iβ/i）降低，表明诱导的β-核较少。在生长方面，发现共聚单体的插入降低了β相的相对生长速率（Gβ/Gα），削弱了β相生长的动力学优势。研究表明，随着共聚单体的加入，β/ α和g β/ g α均降低。DCHT诱导的β-细胞核减少和随后不利的β生长同时导致最终的kβ降低。我们的基本见解提供了一个更全面的理解减少β作为共聚单体插入到iPP链，可能对聚合物的多态性控制具有重要意义。
Compared with polypropylene homopolymer (PPH), β-nucleating agent (β-NA) usually induces less β-phase in polypropylene random copolymer (PPR) with comonomer inserted. A widely held view is that unfavorable β-growth kinetically caused by the insertion of comonomer contributes to a decreased relative content of β-phase (kβ) in PPR. To further understand the decreasedkβin PPR, we separately investigated the nucleation and growth behavior of various isotactic polypropylenes (iPPs) nucleated with a β-NA,N,N′-dicyclohexylterephthalamide (DCHT). With the aid of fractionated crystallization, the possibility of DCHT to form β-nuclei,iβ/i, is calculated to be reduced in PPR with ethylene inserted, demonstrating fewer β-nuclei induced. As for growth, it is found that the insertion of comonomer decreases the relative growth rate of β-phase (Gβ/Gα) and weakens the kinetic advantage of β-growth. The study reveals that bothiβ/iandGβ/Gαdecrease with the insertion of comonomer. Fewer β-nuclei induced by DCHT and the subsequent unfavorable β-growth simultaneously contribute to the final decreasedkβ. Our fundamental insight provides a more comprehensive understanding of the decreasedkβas comonomer is inserted into the iPP chain and could have important implications in the control of the polymorphism of polymers.