Abstract: Polyimide (PI) composite materials have excellent properties and a wide range of uses. In order to meet their different usage scenarios and thermal stability requirements, this article uses the thermal imidization process to prepare PI homogeneous composite membranes. Different content of carbon nanotubes (CNTs) were added to the PAA resin matrix, and its mechanical properties, thermal stability and coefficient of thermal expansion (CTE) were tested. The results show that when the content of CNTs is 0.1%, the tensile strength and elastic modulus of the composite film material increase by 5.6% and 8.3%, respectively. When the content of CNTs increases. The tensile strength and elastic modulus begin to decrease. The addition of CNTs does not change the molecular segments of the composite membrane material and have little effect on the thermal stability of the composite membrane. The resin matrix after CNTs are added is unevenly distributed among the fibers, and evenly accumulates on the surface of the composite membrane. CNTs have a significant effect on reducing the CTE of the composite membrane, and when the CNTs content is 0.1%, the CTE of the composite membrane is the lowest.

Key words: polyimide, carbon nanotubes, mechanical properties, thermal stability, thermal expansion coefficient