Nylon 66/poly(vinyl pyrrolidone) reinforced composites: 1. Interphase microstructure and evaluation of fiber-matrix adhesion

Nylon 66, an aliphatic semicrystalline polyamide, was reinforced with E-gla ss fibers or high-modulus (AS4) carbon fibers. As in many reinforced semicr ystalline thermoplastics, an interphase composed of transcrystallinity deve loped owing to the high nucleation density of the polymer on the fiber surf ace. The influence of this region on the fiber-matrix adhesion was studied with a modified microdebond test. E-glass fibers were freshly prepared in o ur laboratory by traditional glass-forming techniques and embedded in a fil m of Nylon 66 or a Nylon 66/poly(vinyl pyrrolidone) (PVP) blend. Previous w ork has shown that PVP, an amorphous polar polyamide, has a dramatic influe nce on the morphology of Nylon 66. This phenomenon was utilized to manipula te the interphase formation in the Nylon 66 composite from one having a com plete transcrystalline interphase to a composite with the absence of an int erphase. PVP was introduced to the matrix by solution blending with Nylon 6 6 and/or to the fibers as a sizing prior to embedment. The resulting morpho logies were studied by polarized hot-stage optical microscopy. From the mic rodebond and morphology results, it was shown that the fiber-matrix adhesio n in this composite system is dependent upon interphase microstructure. Com posites containing transcrystallinity have higher interfacial shear strengt h values than those that do not contain this interphase. This has profound implications for the bulk mechanical properties of the composite, which are addressed in Part 2 of this paper. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.