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Inorganic fullerene-like WS2 nanoparticle- (IF-WS2) reinforced nylon 12 nanocomposites have been prepared through effective ultrasonic mixing without using any surfactant, followed by molding at 220 °C. Morphological characterizations using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and microcomputed tomography (micro-CT) have revealed the excellent dispersion of IF-WS2 nanoparticles in the nylon 12 matrix. X-ray diffraction (XRD) analyses have confirmed that a phase transition from α'-phase to a more stable γ-phase took place during the sintering of nylon 12, regardless of the amount of IF-WS2 added to the matrix. At a very low IF-WS2 content of 2 wt%, the tensile strength and bending strength of the composites increased slightly by 27% and 28%, respectively. However, the toughness dramatically improved by 185% and 148% at IF-WS2 additions of 0.25 and 0.5 wt%, respectively, when compared to the neat nylon 12. It is believed that such improvements should mainly be attributed to the well-dispersed IF-WS2 within the matrix. The vastly improved toughness suggests that the resulting polymer nanocomposites could be promising for structural and high-performance impact applications.

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Microfocus X-ray diffraction has been used to analyze interfacial stress transfer in twophase polymer systems consisting of a highly oriented polymer fiber in an isotropic resin matrix. Synchrotron radiation has been used to obtain high-quality X-ray diffraction patterns from single poly-(p-phenylene benzobisoxazole) (PBO) and poly(p-phenylene terephthalamide) (PPTA) fibers in these model two-phase systems. Two different specimen geometries were studied: a fully embedded fiber composite and a microdroplet specimen. A procedure is demonstrated whereby well-defined diffraction patterns can be obtained, using a 5 µm diameter X-ray beam, from individual 12 µm diameter polymer fibers in over 1 mm thickness of resin by subtracting the scattering of the resin matrix from that of the fiber and matrix to obtain a diffraction pattern of the fiber only. Shifts of meridional diffraction peaks of the fibers were determined as a function of stress and were converted into crystal strain. The fiber stress was then determined from calibrations obtained from previous X-ray diffraction studies of fiber deformation. The point-to-point variation of fiber stress was mapped along the fibers in the specimens, and a force-balance approach was used to determine the shear stress at the fiber-matrix interface. This present study was concerned only with an optically transparent polymer matrix, but the possible extension of the technique to opaque matrices and other multiphase polymer systems is discussed.

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