Pbzt Microcomposites with Advanced Thermoplastic Matrices
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PBZT MICROCOMPOSITES WITH ADVANCED THERMOPLASTIC MATRICES W. MICHAEL SANFORD AND GERARD M. PRILUTSKI E. I. du Pont de Nemours and Co., Inc., Experimental Station, P.O. Wilmington, Delaware 19880-0302
Box 80302,
Thermoplastic microcomposites offer the potential for better economics and improvements in composite processing, and possibly performance, over conventional "string-and-glue" composites. The early development of molecular composite technology focused on polyamide matrix polymers; however, for many aerospace applications higher use temperatures and greater solvent resistance than that of conventional polyamide matrices will be required. This paper describes work performed under contract to the U.S. Air Force to develop PBZT (poly p-phenylene benzobisthiazole)/thermoplastic molecular composites with high performance matrix resins into a viable technology. A scaleable process has been defined based on a novel technology developed by Du Pont. Advantages of this process include better economics, superior processing performance, and improved MC fiber tensile properties versus prior art. Using this process we have obtained rule-of-mixtures properties in our microcomposite fibers with matrix polymers offering use Consolidation of PBZT/PEKK fibrous preforms temperatures from 330 to 600*F. into uniaxial panels up to 10" x 15" has been demonstrated and material propperty evaluation and data base development are in progress. Uniaxial property levels achieved to date for all systems compare favorably with conventional "string-and-glue" PBZT/epoxy composites although as with other organic fiber reinforcements, compressive and shear performance may be limiting factors in MC applications.
INTRODUCTION Conceptually, molecular composites are dispersions on a molecular scale of rigid rod polymer molecules in a matrix of flexible coil polymers, formed by the coagulation of a dilute isotropic solution containing these components [1-3]. In the original concept, phase segregation of the rod and coil polymers into separate phases was to be avoided, because the rigid rod molecules tended to aggregate to form domains with low aspect ratios ("footballs") which led to ineffective reinforcement and hence low mechanical properties [2]. To avoid phase segregation, very low concentrations (below the critical concentration of 3.5%) were generally used. We have found, however, that under certain conditions, and using higher, more practical, solution concentrations, the rigid rod polymer aggregates to form a fibrillar microscopic rather than molecular dispersion (rod domains of 1,000-10,000 vs.
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