Rheological properties of poly(vinyl chloride)/plasticizer systems—relation between sol–gel transition and elongational viscosity
Rheological properties of poly(vinyl chloride)/plasticizer systems—relation between sol–gel transition and elongational viscosity
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DOI：
10.1007/s00397-007-0178-7
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发表时间：
2007-03
期刊：
影响因子：
2.3
通讯作者：
M. Sugimoto;Hirokazu Hida;T. Taniguchi;K. Koyama;Y. Aoki
中科院分区：
文献类型：
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作者：
M. Sugimoto;Hirokazu Hida;T. Taniguchi;K. Koyama;Y. Aoki
聚氯乙烯(PVC)/邻苯二甲酸二异壬酯（PVC）体系，PVC含量为45.5 （PVC8）和70.4 wt% (PVC6)，在150℃的热辊上制备，在180℃的压力下成型。在150 ~ 220℃范围内测定了PVC8和PVC6的动态粘弹性和伸长粘度。我们发现PVC8和PVC6的存储和损失剪切模量G '和G″分别在190°C和210°C时与角频率ω呈幂律关系。相应地，tanδ值不依赖于ω。这些温度表示每个体系的临界凝胶温度。从这些数据中得到的临界弛豫指数为0.75，与PVC含量无关，这与之前报道的低PVC浓度样品的值一致。这些结果表明，不同增塑剂含量的PVC凝胶具有相似的分形结构。在tgel以下，PVC晶体随着温度的升高而逐渐融化，而在tgel以上，贯穿整个系统的密集连接网络消失了。相应的，PVC8和PVC6的拉伸粘度行为在tgel以下表现出强烈的应变硬化，而在tgel以上没有表现出应变硬化。这些流变行为的变化是由于在这种物理凝胶中作为交联域的PVC晶体的逐渐融化，因此时间-温度叠加不适用于PVC/增塑剂体系。
Poly(vinyl chloride) (PVC)/di-isononyl phthalate systems with PVC content of 45.5 (PVC8) and 70.4 wt% (PVC6) were prepared by a hot roller at 150 °C and press molded at 180 °C. The dynamic viscoelasticity and elongational viscosity of PVC8 and PVC6 were measured in the temperature range from 150 to 220 °C. We have found that the storage and loss shear moduli,G′ andG″, of PVC8 and PVC6 exhibited the power-law dependence on the angular frequencyωat 190 and 210 °C, respectively. Correspondingly, the tanδvalues did not depend onω. These temperatures indicate the critical gel temperatureTgelof each system. The critical relaxation exponentnobtained from these data was 0.75 irrespective of PVC content, which was in agreement with thenvalues reported previously for the low PVC concentration samples. These results suggest that the PVC gels of different plasticizer content have a similar fractal structure. BelowTgel, the gradual melting of the PVC crystallites takes place with elevating temperature, and aboveTgel, a densely connected network throughout the whole system disappears. Correspondingly, the elongational viscosity behavior of PVC8 and PVC6 exhibited strong strain hardening belowTgel, although it did not show any strain hardening aboveTgel. These changes in rheological behavior are attributed to the gradual melting of the PVC crystallites worked as the cross-linking domains in this physical gel, thereby inapplicability of the of time–temperature superposition for PVC/plasticizer systems.