Polyethylene (PE)/maleic anhydride grafted PE (g-PE)/expanded graphite (EG) electrically conductive nanocomposites were successfully prepared by solution intercalation (SI) and masterbatch melt mixing (MMM). Electrical conductivity () measurements; transmission electron, scanning electron, and optical miscroscopy observations; and differential scanning calorimetry analyses were employed to examine the influences of the preparation methods, EG volume or weight fractions ( or f w ), and g-PE weight contents (C g ) on the structure and of the nanocomposites, as compared to PE/g-PE/EG composites and PE/EG control produced by direct melt mixing (DMM). The percolation thresholds ( c ) of the SI, MMM, and DMM composites (C g /f w ϭ 1.5) and the DMM control were measured and found to be 2.19, 3.81, 4.68, and 5.35%, respectively. As the C g /f w increases from 1 to 4, the of the MMM and DMM composites with f w ϭ 9% rises from the order of 10 Ϫ16 to 10 Ϫ4 and 10 Ϫ8 S/cm, respectively. These were closely associated with the morphology and microstructure of the composites varying with the preparation methods ( and C g /f w ) and could also be interpreted in terms of percolation theory.

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The reinforced poly(propylene) (PP)/poly(ethylene terephthalate) (PET) in‐situ fiberized composites were prepared by extrusion‐drawing‐injection molding. The influences of PET weight fraction (fw) on the PET fiberization, phase morphology, and mechanical properties of the composites, together with their functional mechanisms were studied by contrast to the normal‐blended materials without drawing. The results show that as the fw rises from 0 to 20%, the number of PET fibers increases, whereas their diameter and dispersity decrease till fw = 15% and then increase, and the number of remained PET particles tends to rise. These changes of PET fiberization and phase morphology with fw were attributed to the consequence of the combined actions of breakup, coalescence, and deformation of the PET dispersed phase in the PP matrix during the extrusion drawing. Correspondingly, the tensile strength (σt) and Young's modulus (E) of the in‐situ composites increase till fw = 15% and then decrease, with maximum gains of σt and E of about 20 and 70% relative to the neat PP, respectively. This σt/fw relation was ascribed to the counterbalanced result between the reinforcing effect of the dispersed phase on matrix and the interfacial flaw effect of two immiscible phases, while the E/fw relation was considered as a representation of the rigidizing effect of the fibers on the matrix being controlled by both their number and diameter.In‐situ PET fibres (PET/PP = 85/15) in an as‐drawn filament.magnified imageIn‐situ PET fibres (PET/PP = 85/15) in an as‐drawn filament.