Composition Dependence of Viscosity of Ethylene Ionomer Blends
Composition Dependence of Viscosity of Ethylene Ionomer Blends
复制标题
乙烯离聚物共混物粘度的组成依赖性
DOI：
10.1678/rheology.30.155
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发表时间：
2002
影响因子：
1.3
通讯作者：
K. Koyama
中科院分区：
文献类型：
--
作者：
Mihoko Nishio;A. Nishioka;Tatsuhiro Takahashi;J. Takimoto;K. Koyama
由钠或锌等金属离子部分中和的聚（乙烯-甲基丙烯酸）（EMAA）是最广泛使用的离聚物之一。这些乙烯离聚物的固态结构和机械性能已得到广泛研究，最近出版了一本评论书。1) 还研究了钠或锌乙烯离聚物熔体的粘弹性，以阐明熔融状态下离子的作用。2-4) 特别是，Vanhoorne 和 Register5) 研究了未中和酸基团的质子对部分中和的 EMAA 离聚物熔体流变学的影响。通过酸基团的醚化除去质子，他们发现质子在钠离聚物中的作用与在锌离聚物中的作用不同。5）在钠离聚物中，一个钠离子不仅与一个COO配对，而且还与两个COOH酸基配位，并且钠离子和质子可以在COONa和COOH之间交换。这种“酸-阳离子交换”机制5）允许聚合物链段轻松地从一个离子聚集体扩散到其他离子聚集体，并降低链段运动的摩擦。另一方面，在锌离聚物的情况下，锌离子与两个COO基团配位，并且离子附近不存在COOH基团。因此，不会发生酸-阳离子交换，并且在同等中和条件下，锌离聚物比钠离聚物具有更高的粘度（和更长的弛豫时间）。在本文中，为了更深入地了解离子在熔体流变学中的作用，研究了两个系列共混物的动态剪切模量，即（1）EMAA 和 EMAA 钠离聚物的共混物，以及（2）EMAA 钠和锌离聚物的共混物，作为共混比的函数。在前一种共混物的情况下，零剪切粘度作为组成的函数遵循对数加法规则，而在后一种共混物中观察到与对数加法规则的强烈负偏差。将给出这一发现的可能解释。
Poly(ethylene-co-methacrylic acid) (EMAA) partially neutralized by metal ions such as sodium or zinc is one of the most widely used ionomers. Structure and mechanical properties in the solid state of these ethylene ionomers have been extensively investigated, and a review book was recently published.1) Viscoelastic properties of sodium or zinc ethylene ionomer melts have also been studied to clarify the role of ions in the molten state.2-4 ) Especially, Vanhoorne and Register5) studied the effect of the protons of unneutralized acid groups on the melt rheology of partially neutralized EMAA ionomers. By removing the protons by etherification of the acid group, they have found that the role of the protons in sodium ionomers is different from that in zinc ionomers.5) In the case of sodium ionomers, a sodium ion is not only paired with one COO but also coordinated with two COOH acid groups, and the sodium ion and a proton can be exchanged between COONa and COOH. This “acid-cation exchange” mechanism5 ) allows a polymer segment to easily diffuse from one ion aggregate to others, and lowers the friction for the segmental motion. In the case of zinc ionomers, on the other hand, a zinc ion is coordinated with two COO groups, and no COOH group exists near the ion. Thus the acid-cation exchange does not take place, and the zinc ionomer has much higher viscosity (and longer relaxation time) than the sodium ionomers at equivalent neutralization. In this paper, in order to get deeper insight into the role of ions in the melt rheology, dynamic shear moduli of two series of blends, (1) blends of EMAA and EMAA sodium ionomer,and (2) blends of EMAA sodium and zinc ionomers, were examined as a function of the blend ratio. In the case of the former blends, the zero shear viscosity as a function of composition followed the log additively rule, while a strong negative deviation from the log additively rule was observed in the latter blends. A possible explanation of this finding will be given.