Cocrystallization and Phase Segregation of Polyethylene Blends between the D and H Species. 7. Time-Resolved Synchrotron-Source Small-Angle X-ray Scattering Measurements for Studying the Isothermal Crystallization Kinetics: Comparison with the FTIR Data
Cocrystallization and Phase Segregation of Polyethylene Blends between the D and H Species. 7. Time-Resolved Synchrotron-Source Small-Angle X-ray Scattering Measurements for Studying the Isothermal Crystallization Kinetics: Comparison with the FTIR Data
复制标题
D 和 H 物种之间聚乙烯共混物的共结晶和相分离。
DOI：
10.1021/ma00129a003
复制
发表时间：
1995
期刊：
影响因子：
5.5
通讯作者：
R. Stein
中科院分区：
文献类型：
--
作者：
K. Tashiro;Kouji Imanishi;Y. Izumi;Masamichi Kobayashi;Katsumi Kobayashi;M. Satoh;R. Stein
用同步辐射技术测量了全氘代高密度聚乙烯（DHDPE）与不同乙基支化度的含氢聚乙烯共混物熔体等温结晶过程的时间分辨小角X射线散射。由不变量的时间依赖性估算出纯组分的结晶速率顺序为HDPE >> DHDPE > LLDPE（2）>> LLDPE（3），其中HDPE为无支化的高密度聚乙烯（PE），LLDPE（2）为线性低密度聚乙烯（LLDPE），约100 ℃。17个乙基支链/1000 ℃，LLDPE（3）是具有约41个分支。DHDPE和LLDPE（2）的相似结晶速率可能是D和H物种之间共结晶行为的重要原因之一。DHDPE/HDPE或DHDPE/LLDPE（3）的双组分体系基本上表现出D和H晶型层间的相分离现象，这可能是由于D和H晶型层间结晶速率差异较大所致。已经发现，显示出共结晶现象的DHDPE/LLDPE（2）共混物的样品比原始纯组分更快地结晶;即，对于共混物已经观察到加速效应。另一方面，在D/H对显示相分离的情况下，DHDPE/HDPE和DHDPE/LLDPE（3）共混物，共混后结晶速率大大降低。从晶体的反式谱带强度，这是在时间分辨FTIR实验中测得的，已被发现的结晶速率显着高于从SAXS测量评价的不变量。这一发现首次在实验上支持了以下结晶机制：首先从熔融的无规卷曲中产生反式锯齿形链段，然后这些反式链段聚集在一起形成小的结晶簇，这些结晶簇生长成较大的薄片，如小角X射线散射测量所检测到的。
Time-resolved small-angle X-ray scatterings have been measured by using synchrotron radiation for the isothermal crystallization process from the melt of the blends between the fully deuterated high-density polyethylene (DHDPE) and the hydrogeneous polyethylene with various degree of ethyl branching. The crystallization rate of the pure components estimated from the time dependence of the invariant is in the order of HDPE >> DHDPE > LLDPE(2) >> LLDPE(3), where HDPE is a high-density polyethylene (PE) without branching, LLDPE(2) is a linear low-density PE with ca. 17 ethyl branches/1000 C, and LLDPE(3) is a LLDPE with ca. 41 branchings. The similar crystallization rates of DHDPE and LLDPE(2) may be one of the most important origins governing the cocrystallization behavior between the D and H species. Pairs of DHDPE/HDPE or DHDPE/LLDPE(3) show basically the phase segregation phenomena between the D and H crystalline lamellae, possibly originating from the large difference in the crystallization rate between the D and H species. It has been found that the sample of DHDPE/LLDPE(2) blend, which shows the cocrystallization phenomenon, crystallizes faster than the original pure components ; i.e., an acceleration effect has been observed for the blend. On the other hand, in the cases where the D/H pair shows the phase segregation, DHDPE/HDPE and DHDPE/LLDPE(3) blends, the crystallization rate has been found to be reduced largely after blended. The crystallization rate viewed from the crystalline trans band intensity, which was measured in the time-resolved FTIR experiments, has been found to be remarkably higher than that of the invariant evaluated from the SAXS measurement. This finding supports, for the first time, experimentally the following crystallization mechanism : the trans-zigzag chain segments are generated at first from the molten random coils and then these trans segments gather together to form small crystalline clusters, which grow into larger lamellae, as detected by the small-angle X-ray scattering measurement.