Processing and properties of polyimide melt blends containing a thermotropic liquid crystalline polymer

Abstract

Abstract Several polymer blend compositions of LaRC‐TPI 1500 and New TPI 450 (Mitsui Toatsu) with Xydar SRT 900 LCP (Amoco Performance Products) were extrusion processed. In addition to binary blends containing one TPI with an LCP, ternary blends consisting of an alloy containing both TPIs as the matrix were also processed. By varying the ratio of the polyimides in the matrix, the blends' thermal behavior could be tailored. This paper addresses both processing issues and film properties of these blends. Rheological and thermal studies were conducted on both blends made in a torque rheometer and on biaxially oriented film produced with a counter‐rotating annular die. These biaxial blend films were further characterized by measuring tensile and electrical properties. For 70/30 New TPI/Xydar equal biaxial films of 50 μm thickness, a modulus of 3.8 GPa and a stress at break of 100 MPa were measured. For near uniaxial blend films (±3°) a modulus of 14.5 GPa and a strength of 220 MPa in the machine direction (MD) were measured. The transverse direction (TD) properties were still higher than the neat New TPI. The electrical properties of these blends were outstanding. The dissipation factor was typically less than 0.01 for most blend compositions. Similarly, the dielectric constant was typically less than 3 up to temperatures as high as 300°C.