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.

: This Phase I SBIR program is applying a proprietary interface- modification process to improve the interaction between glass fibers and thermoplastic resin composite matrices. In our accomplishments thus far, we have selected PEEK as the thermoplastic matrix resin and chosen three candidate interface-modifier resins. Fiber wetting experiments will determine which of these candidates is best suited for use on the program. A glass fiber tow spreader that effectively separates the tow into a narrow ribbon of fibers was constructed. Extraction experiments have demonstrated that the oil-based, PEEK compatible sizing can be effectively removed from glass fibers without damage by extraction with an appropriate solvent. Equipment was constructed for winding separated glass tow onto a large diameter drum, then processing the separated tow to remove the present sizing and coat with interface-modifier resin solution while the fibers remain in place upon the drum. Coated fibers will also be staged-dried and heat-treated in place, forming interface-modified glass fibers that have been protected from abrasive damage during the entire interface- modification process.

Sol-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.