Preparation Of Polyimide/ Polyacrylonitrile Blend Pre-Oxidized Fiber And Study Of Its Structure And Properties

This paper aims to produce a blend of fibers and explore a spinning process which can make the polyimide (PI) and polyacrylonitrile (PAN) characteristics compat easily. This kind of polyimide/polyacrylonitrile (PI/PAN) blend fiber can not only be used as a high-performance fiber directly, but also be used to produce the carbon fiber.The mechanical blending method was used to produce the PAA/ PAN blend spinning solution. PAA solution is a terpolymer system which consists of BPDA/p-PDA/ODA (BPO). The compatibility of PAA/PAN system was tested by the phase contrast microscopy and the result showed that PAA/PAN blends have a good compatibility. Wet spinning was used to process PI fibers, PAN fibers and PI/PAN fibers, the structure and properties of which were tested by FTIR,2D-WAXD, DSC, DMA, SEM, and fiber strength tester.This paper studied the effects of different heat treatment time on structures and properties of PI fibers, PAN fibers and PI/PAN fibers. The results showed that as for PI fibers, with the growth of the heat treatment time, the degree of imidization increased, while the degree of orientation, lateral degree of order and mechanical properties of the fibers increased at first and then decreased. When the heat treatment time was 3 minutes, the fiber had the best strength of 1082MPa. As for PAN fibers, with the growth of the heat treatment time, the degree of pre-oxidation increased, while the strength of fiber increased at beginning and then decreased. As for PI/PAN fibers, degree of imidization and pre-oxidation also increased which was the same as the pure system, but these fibers had more increment than the pure system under the same conditions. When the heat treatment time was 10 minutes, the fiber had the best strength of 1151MPa. In addition, PI fiber made much greater contribution to the mechanical properties of the blend system.This paper also studied the effects of the mass ratio on the structure and properties of PI/PAN fibers, in whih 23%,33% and 43% of PAN content were used. The results showed that with the increase of PAN content, the degree of imidization and orientation in meridian direction increased at first and then decreased, while the degree of pre-oxidation decreased and orientation in equatorial direction gradually increased. When the PAN content was 23%, the system processed the best mechanical properties and PAA/PAN blends had a good compatibility.