Film Processing and Applications for Rigid-Rod Polymers

ABSTRACTHigh strength, high modulus (2 GPa, 270 GPa, respectively) films have been produced with controllable planar orientation. Films were extruded from high viscosity nematic polymer solutions using rigid-rod aromatic heterocyclic polymers. Novel solution processing and treatment were used to control orientation, microfibrillar structure and texture, and physical properties. The coefficient of thermal expansion of these films was tailored by orientation and addition of secondary materials. This resulted in applications for dimensionally stable electronic substrates and structures for spacecraft. Other applications include high temperature barrier films, thin-walled structures, lightweight capacitors, high temperature insulation and cryogenic tanks.</jats:p

Improvement of Compressive Strength in Ordered Polymer Films and Fibers by Sol-Gel Glass Processing

ABSTRACTSol-gel glass processing of poly (benzobisthiazole) (PBZT) films increased the compressive strength of PBZT/PEEK film laminates by more than four times, with the potential for further improvement indicated. This was accomplished by infiltrating sol-gel glass precursor reagents into microfibrillar regions of PBZT film, forming PBZT/sol--gel glass microcomposites that combined the high compressive strength of glass with the exceptional strength and toughness of PBZT ordered polymer. The presence of glass within PBZl/sol-gel microcomposite films inhibited the buckling of microfibrils during film compression, greatly increasing the resistance of the films to compressive failure. The use of sol-gel glass compositions that fuse at temperatures within thermal stability limits of PBZT (600 C) should further improve PBZI film compressive strength.Preliminary experiments involving sol-gel processing of PBZT fibers did not show improvements in fiber compressive strength. Microscopic analysis of treated fibers indicated that fiber abrasion and kinking had occurred during batch processing steps.The results of our continuing efforts to achieve 100 Ksi compressive strength in PBZT films and fibers will be discussed.</jats:p

Biaxial Extrusion of Polyimide Larc—tpi and Larc—tpi Blends

ABSTRACTBiaxial 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 new extrusion technique. Three types of films, neat LARC—TPI, LARC—TPI/lO wt percent and 30 wt percent blends were processed as a part of this NASA funded program. This new process offers an alternative technique to costly post—processing stretching of both solution cast and sheet extruded films. The post—processing step is often required to enhance certain properties. Processability was greatly enhanced by incorporating Xydar. The coefficient of thermal expansion was reduced from 34 ppm/ºC for the neat LARC—TPI to 15 ppm/º C for the 10 wt percent Xydar blend and ultimately down to I to 3 ppm/º C for the 30 wt percent blend films in the direction of extrusion. The maximum improvementin stiffness was realized by incorporating 10 wt percent 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.</jats:p

Poly [Benzobis Thiazole] (PBT)/SOL-GEL Microcomposites

The objective of this Small-Bus i ness Innovative Research (SBIR) effort is to expand on work reported previously [1] and further develop a new class of microcomposite materials which combine the outstanding properties of ordered polymers and the excellent compressive strength of glass. In Phase I we demonstrated adverse property changes in poly(p-phenylene benzobisthiazole) (PBT) ordered polymer films by infiltrating sol-gel glass reagents. During Phase II we have addressed the following areas: sol-gel infiltration process; effect of sol-gel glass composition; tensile strength characterization, microcomposite UV resistance, lamination process, compressive strength determination. The following subsections present the work conducted to date.</jats:p