Li Yijun, Wen Xinyu, Nie Min, Wang Qi
State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China.
ACS Omega. 2017 Oct 26;2(10):7230-7238. doi: 10.1021/acsomega.7b01036. eCollection 2017 Oct 31.
Dendritic β-nucleating agent (β-NA) can readily manipulate the formation of dendritic β-crystal with a unique toughening effect on polypropylene (PP) to drastically enhance the ductility. However, by the current method, the geometric size is too large to fully perform the nucleating efficiency. In this study, by comparatively investigating the effect of molecular weight of PP and diffusion of β-NAs in a PP melt, we proposed a novel carrier strategy that selective enrichment of β-NAs in a PP carrier was followed by directed migration into polymer matrix. Accordingly, the growth of NAs was controlled by the release from the PP carrier, which decreased the available amount of β-NAs during the growth stage. In this case, the viscosity difference between PP carrier and matrix determined the interfacial movement of β-NAs. When the PP carrier and matrix had same molecular weight, the diffusion and release became favorable to facilitate the formation of the dense and fine dendritic aggregates. As a result, the relative content of β-crystals reached 92%, with a drastic increase of ∼82% in the optimal condition compared to the directed compounded PP/β-NAs sample. This study can open a new avenue to tailor the topologies of β-NAs and the ensuing β-crystals for high-performance PP products.
树枝状β成核剂（β-NA）能够轻易地控制树枝状β晶体的形成，对聚丙烯（PP）具有独特的增韧作用，可显著提高其延展性。然而，按照目前的方法，其几何尺寸过大，无法充分发挥成核效率。在本研究中，通过比较研究PP分子量和β-NA在PP熔体中的扩散的影响，我们提出了一种新型载体策略，即先在PP载体中选择性富集β-NA，然后将其定向迁移到聚合物基体中。相应地，β-NA的生长由PP载体的释放来控制，这减少了生长阶段β-NA的可用量。在这种情况下，PP载体与基体之间的粘度差异决定了β-NA的界面移动。当PP载体与基体具有相同分子量时，扩散和释放变得有利于促进致密且细小的树枝状聚集体的形成。结果，β晶体的相对含量达到92%，在最佳条件下与直接复合的PP/β-NA样品相比急剧增加了约82%。本研究可为定制β-NA的拓扑结构以及由此产生的β晶体以用于高性能PP产品开辟一条新途径。
