新中间相沥青的制取和性质的研究

PREPARATION AND PROPERTIES OF NEOMESOPHASE PITCH

本文采用一系列不同溶解度参数的混合溶剂对聚合石油沥青分别进行抽提,获得的四个组分用热台显微镜观察,发现它们是典型的新中间相组分,它们在熔融后直接转化成各向异性的中间相熔并体,而不是经过中间相小球的生成、长大、熔并这个通常的过程。热台显微镜试验同时证明,中间相的形成过程以一个物理过程作为控制步骤。对四个新中间相组分还进行了热重、分子量及分子量分布等研究,结果表明,最高加热温度为700℃时,失重量范围在16.7～34.0m％之间,且它们的分子量分布仅略微不同。不同溶解度参数δ抽出的新中间相组分的性质呈现规律性变化,如δ增大时,H/C原子比减小,分子量增高、软化点提高、失重量减少,芳香性增加等。由软化点数据和可纺性测试证明了将新中间相沥青纺制成高性能沥青碳纤维的可行性。

The heptane insoluble and tetrahydrofuran soluble fractions (HI-THFS) of the polycondensed petroleum pitch were seperately extracted by four solvent mixtures with increasing solubility parameters, and respective subfractions with progressively larger average molecular size were obtained. The hotstage microscopic observation revealed the typical neomesophase behaviors of all seperated samples. They transformed into anisotropic bulk mesophase as soon as melted, rather than went through a common process of mesophase nucleation, growth and coalescence. It was proposed that the formation of mesophase from mesogens of the subfractions was physically controlled by van der Waals force,while the formation of the mesogen itself could be a chemical process as in the heat treatment system. Some properties of the subfractions (including H/C atomic ratio, E1600/E1450, MW, softening point, molecular weight distribution and weight loss, etc.) exibited a regular change with increasing solubility parameter of the solvent mixtures. These findings can be chosen as a basis for controlling the properties of the extracted subfractions, making them to have satisfactory spinnability, thermal stability, and rheological performance. The work accomplished in this paper has verified the possibility of preparing high performance carbon fiber from the neomesophase samples.