熔融中间相沥青的流动性

FLOW OF MOLTEN MESOPHASE PICTH

熔融中间相沥青的流变性能,在科学研究中已成为人们迫切需要了解的问题。同时,在技术上也是极其重要的。然而,除近年来一点研究外,早期的实验技术不完全适合于描述熔融中间相沥青这类复杂液体的流变特性。因此,关于中间相沥青流变性能的资料似乎并不很多。而且精确测定碳质各向异性物质的表观粘度是困难的。本文讨论了引起这些困难的主要因素。为了测定中间相沥青的表观粘度,对一个Couette流变仪进行了改进,用以克服实验中的大量困难。关于这个装置的可靠性也进行了试验,对于多种流体的表观粘度,其测量值与用其它两种流变计(Instron Capittary和Seiscor/Han)所测得的数值进行横向校对。现在,用改良的Couette流变仪,采用先进的技术,研究了工业用沥青完全转变为各向异性沥青的过程中流变性质的变化。为了比较,也研究了两种由模拟化合物制得的中间相沥青的流变性。

The rheological behaviour of molten mesophase pitch has become a subject of major scientific curiosity as well as technological importance. With the exce- ption of a few recent studies, the early experimental techniques were not enti- rely adequate for precise rheological characterization of such a complex fluid as molten mesophase pitch. A reasonably extensive literature, therefor, does not seem to exist on mesophase pitch rheology. The factors which could contribute to the difficulties of accurately measuring the apparent viscosity of carbonace- ous anisotropic materials are discussed herein. A Couette-flow instrument has been modified for measuring the apparent viscosity of mesophase pitch,circum- venting most of the experimental difficulties. The reliability of this apparatus has been tested by cross checking the apparent viscosity measurements with the va- lues measured from two other rheometers, Instron Capillary and Seiscor/Han, for a number of fluids. Changes in rheological properties that occur during the transformation of a commercial pitch into a totally anisotropic pitch have now been studied by an improved technique on the modified Couette apparatus. The rheology of two mesophase pitches, made from model compounds, have also been investigated for comparison.