不同代数端羟基超支化聚酯及其二元共混物的流变行为

系统研究了消除热历史后的G1~G5端羟基超支化聚酯熔体及组分质量比为1∶1的二元共混物的流变行为。结果表明,无论是稳态剪切测试还是振荡测试,消除热历史后的G2~G5端羟基超支化聚酯熔体均表现为牛顿流体的流变行为。G3~G5端羟基超支化聚酯的流变行为均遵循Cox-Merz方程。G2端羟基超支化聚酯在振荡测试的高频区出现了剪切增稠现象。对于组分质量比为1∶1的低代/高代端羟基超支化聚酯二元共混物,无论是稳态剪切还是振荡剪切,只要一种组分是牛顿流体,那么二元共混体系也是牛顿流体。高代数组分决定了二元共混物的流变特性,而低代数组分主要影响二元共混物的黏度。

Rheological Behavior of Different Generations of Hydroxyl-terminated Hyperbranched Polyesters and Their Binary Blends

The rheological behavior of the first to the fifth generation of hydroxyl-terminated aliphatic hyperbranched polyesters and their binary blends consisting of two generations of hyperbranched polyesters with a weight ratio of unity were studied by rotational rheometer. The results showed that the second to the fifth generation of hydroxyl-terminated hyperbranched polyesters showed Newtonian fluid behavior in both steady shear and oscillatory shear conditions after eliminating thermal history. The Cox-Merz rule was found to be obeyed by the third to the fifth generation of hydroxyl-terminated hyperbranched polyesters. Due to the stronger ability of crystallization, the second generation of hydroxyl-terminated hyperbranched polyester showed shear-thickening behavior at high frequency region of oscillatory shear pattern while increasing temperature under the condition of exerting oscillation shear force within a small amplitude. The binary blends consisting of two generations of hyperbranched polyesters with a weight ratio of unity showed only Newtonian characteristics in both steady shear and oscillatory shear conditions if at least one of the components was Newtonian. The higher generation component dictated the flow characteristics of the binary blends and the lower generation portion affected the viscosity.