Biaxial extrusion of polyimide LARC-TPI and LARC-TPI blends

Biaxial films of polyimide LARC-TPI and LARC-TPI/liquid crystal polymer Xydar were extruded directly from the melt for the first time via an innovative extrusion technique. Three types of films, neat LARC-TPI, LARC-TPI/10 wt pct and 30 wt pct blends were processed as a part of this NASA-funded program. Processability was greatly enhanced by incorporating Xydar. The coefficient of thermal expansion was reduced from 34 ppm/C for the neat LARC-TPI to 15 ppm/C for the 10 wt pct Xydar blend and ultimately down to 1 to 3 ppm/C for the 30 wt pct blend films in the direction of extrusion. The maximum improvement in stiffness was realized by incorporating 10 wt pct Xydar (2.8 GPa up to 4.9 GPa). Tensile strength, however, experienced a drop as a result of Xydar addition, probably caused by inefficient mixing of the two phases.