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Agglomeration of Crystals during Crystallization of Semicrystalline Polymers: A Suspension-Based Rheological Study
Macromolecules ( IF 5.1 ) Pub Date : 2019-01-25 00:00:00 , DOI: 10.1021/acs.macromol.8b02452 Peng He 1 , Wei Yu 1 , Chixing Zhou 1
Macromolecules ( IF 5.1 ) Pub Date : 2019-01-25 00:00:00 , DOI: 10.1021/acs.macromol.8b02452 Peng He 1 , Wei Yu 1 , Chixing Zhou 1
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The agglomeration of spherulites during isothermal crystallization of olefin multiblock copolymers and the role of mesophase separation on the agglomeration behavior were investigated by a new rheological method, which is based on the analogy between crystal morphology and particle suspension in polymeric matrix. The new suspension-based rheological method solved the problem of frequency dependency, which was encountered in the traditional rheological study in determination of the fraction of transformation. It was achieved by decomposing the time-resolved dynamic moduli during crystallization into the hydrodynamic part and the agglomerates’ part using a two-step shifting procedure. The relative crystallinity determined from the product of two shifting factors, the strain rate amplification factor and the stress amplification factor, was consistent with the DSC measurements. Moreover, the dependence of the agglomerates’ contribution to the storage modulus of the crystal (GAgg′) on its volume fraction (ϕrheo) was found to be independent of the crystallization temperature, resulting in a master curve GAgg′ vs ϕrheo that could be used as a unique parameter to characterize the agglomeration of spherulites. For olefin block copolymers with similar hard-block content (or crystallinity), it was found that mesophase separation not only delayed the agglomeration of spherulites but also changed its packing behavior. Comparisons with polymer nanocomposites further illustrated the differences in the spatial distribution and agglomeration of “fillers” in polymer nanocomposites, homogeneous semicrystalline polymers, and heterogeneous semicrystalline polymers.
中文翻译：
半结晶聚合物结晶过程中晶体的团聚：基于悬浮的流变学研究
采用一种新的流变学方法，研究了烯烃多嵌段共聚物等温结晶过程中球晶的团聚以及中间相分离对团聚行为的影响。新的基于悬浮液的流变方法解决了频率依赖性的问题，这在传统流变学研究中确定转化分数时会遇到。它是通过使用两步平移程序将结晶过程中的时间分辨动态模量分解为水力部分和团聚体部分来实现的。相对结晶度是由两个位移因子（应变率放大因子和应力放大因子）的乘积确定的，与DSC测量结果一致。此外，附聚物对晶体储能模量的依赖性（ģ此Agg '）在它的体积分数（φ流变）被发现是独立于结晶温度，导致了主曲线ģ此Agg ' VSφ流变，可以用来作为唯一的参数来表征球晶的附聚。对于具有类似硬嵌段含量（或结晶度）的烯烃嵌段共聚物，发现中间相分离不仅延迟了球晶的团聚，而且改变了其堆积行为。与聚合物纳米复合材料的比较进一步说明了聚合物纳米复合材料，均相半结晶聚合物和非均相半结晶聚合物中“填料”的空间分布和聚集的差异。
更新日期：2019-01-25
中文翻译：
半结晶聚合物结晶过程中晶体的团聚：基于悬浮的流变学研究
采用一种新的流变学方法，研究了烯烃多嵌段共聚物等温结晶过程中球晶的团聚以及中间相分离对团聚行为的影响。新的基于悬浮液的流变方法解决了频率依赖性的问题，这在传统流变学研究中确定转化分数时会遇到。它是通过使用两步平移程序将结晶过程中的时间分辨动态模量分解为水力部分和团聚体部分来实现的。相对结晶度是由两个位移因子（应变率放大因子和应力放大因子）的乘积确定的，与DSC测量结果一致。此外，附聚物对晶体储能模量的依赖性（ģ此Agg '）在它的体积分数（φ流变）被发现是独立于结晶温度，导致了主曲线ģ此Agg ' VSφ流变，可以用来作为唯一的参数来表征球晶的附聚。对于具有类似硬嵌段含量（或结晶度）的烯烃嵌段共聚物，发现中间相分离不仅延迟了球晶的团聚，而且改变了其堆积行为。与聚合物纳米复合材料的比较进一步说明了聚合物纳米复合材料，均相半结晶聚合物和非均相半结晶聚合物中“填料”的空间分布和聚集的差异。
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