Wang Yuan-Xia, Wang Chen-Chen, Shi Ying, Liu Li-Zhi, Bai Nan, Song Li-Fu
Advanced Manufacturing Institute of Polymer Industry, Shenyang University of Chemical Technology, Shenyang 110142, China.
College of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142, China.
Polymers (Basel). 2021 Dec 30;14(1):139. doi: 10.3390/polym14010139.
The dynamic crosslinking method has been widely used to prepare rubber/plastic blends with thermoplastic properties, and the rubber phase is crosslinked in these blends. Both polyolefin elastomer (POE) and ethylene-propylene-diene monomer rubber (EPDM) can be crosslinked, which is different from usual dynamic crosslinking components. In this paper, dynamic crosslinked POE/EPDM blends were prepared. For POE/EPDM blends without dynamic crosslinking, EPDM can play a nucleation role, leading to POE crystallizing at a higher temperature. After dynamic crosslinking, the crosslinking points hinder the mobility of POE chains, resulting in smaller crystals, but having too many crosslinking points suppresses POE crystallization. Synchrotron radiation studies show that phase separation occurs and phase regions form in non-crosslinked blends. After crosslinking, crosslinking points connecting EPDM and part of POE chains, enabling more POE to enter the EPDM phase and thus weakening phase separation, indicates that dynamic crosslinking improves the compatibility of POE/EPDM, also evidenced by a lower β conversion temperature and higher α conversion temperature than neat POE from dynamic mechanical analysis. Moreover, crosslinking networks hinder the crystal fragmentation during stretching and provide higher strength, resulting in 8.3% higher tensile strength of a 10 wt% EPDM blend than neat POE and almost the same elongation at break. Though excessive crosslinking points offer higher strength, they weaken the elongation at break.
动态交联法已被广泛用于制备具有热塑性的橡胶/塑料共混物，且在这些共混物中橡胶相是交联的。聚烯烃弹性体（POE）和三元乙丙橡胶（EPDM）均可发生交联，这与通常的动态交联组分有所不同。本文制备了动态交联的POE/EPDM共混物。对于未进行动态交联的POE/EPDM共混物，EPDM可起到成核作用，导致POE在较高温度下结晶。动态交联后，交联点阻碍了POE链的移动，导致晶体变小，但过多的交联点会抑制POE结晶。同步辐射研究表明，在未交联的共混物中会发生相分离并形成相区。交联后，交联点连接EPDM和部分POE链，使更多的POE进入EPDM相，从而减弱了相分离，这表明动态交联提高了POE/EPDM的相容性，动态力学分析也证明了这一点，即与纯POE相比，其β转变温度更低，α转变温度更高。此外，交联网络阻碍了拉伸过程中的晶体破碎并提供了更高的强度，使得含10 wt% EPDM的共混物的拉伸强度比纯POE高8.3%，且断裂伸长率几乎相同。尽管过多的交联点提供了更高的强度，但它们会削弱断裂伸长率。
