Synergies among the self-assembled β-nucleating agent and the sheared isotactic polypropylene matrix
作者：Changyan Zhang, Bo Wang, Jingjing Yang, Guoqiang Zheng(通訊作者), Daowei Ding, Xingru Yan, Kun Dai, Chun
關鍵字：b-nucleating agent, Phase, Self-assembly
論文來源：期刊
發表時間：2015年
The impacts of both shear temperature and shear rate on both the self-assembled bnucleating agent (bNA) in the hosting isotactic polypropylene (iPP) matrix and the subsequent crystallization of the hosting iPP matrix were investigated by polarized optical microscopy (POM) and wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS) measurements, respectively. Under static condition, bNA could self-assemble into snowflake like aggregate. Once shear was applied, three kinds of selfassembled aggregates could be developed prior to the crystallization of matrix depending on the applied shear temperatures, that is, snowflake-like self-assembled aggregate at 200 oC, deformed snowflake-like one with smaller branches at 180 oC, tiny and dense needle-like one if shear temperature was further decreased to 160 oC. Since b-NA with various self-assembled aggregates can act as nucleating templates for the subsequent nucleation of iPP matrix, it is conceivable that the crystallization behavior of the iPP matrix can be altered. As expected, b-phase crystallinity, long period and lamellar thickness are steadily dependent on the shear temperature and shear rate. That is, when shear was applied at 200 oC, b-phase crystallinity, long period and lamellar thickness keeps almost constant regardless of the shear rate. If melt was sheared at 180 oC, b-phase crystallinity was decreased while long period and lamellar thickness remained unchanged with elevating shear rate. At lower shear temperature (i.e., 160 oC), bphase crystallinity, long period and lamellar thickness were further decreased with increasing the shear rate. These results are of practical significance to understand the long-term ignored issue: apart from the loading of b-NA, different self-assembled aggregates formed in flow field are another crucial factor in determining the microstructure development of matrix.