To　improve　the　thermal　and　mechanical　properties　of　isotactic　polypropylene　(iPP),　iPP/Kevlar　fiber　(KF)/polyamide　6　(PA6)　composites　were　prepared　via　the　melt-extrusion　method　on　twin-screw　extruder.　Kevlar　fiber　was　modified　with　caprolactam　using　toluenediisocyanate　(TDI)　as　bridge.　The　microstructure　of　modified　KF　was　successfully　characterized　by　Fourier　transform　infrared　(FT-IR),　X-ray　photoelectron　spectrometer　(XPS)　and　scanning　electron　microscopy　(SEM),　the　results　showed　that　KF　was　bonded　with　caprolactam　and　became　coarser.　Then　the　modified　KF　was　introduced　into　iPP,　the　composites　have　better　mechanical　and　thermal　properties,　implying　that　modification　of　KF　was　helpful　to　improve　the　interfacial　interaction　of　iPP/KF/PA6　composites.　Besides,　the　crystallization　curves　indicated　that　crystallization　behavior　of　PA6　in　the　composites　was　homogeneous　and　fractional.　Furthermore,　compatibilizer　content　played　an　important　role　in　the　mechanical　and　thermal　properties　of　composites.　Crown　Copyright　(C)　2011　Published　by　Elsevier　Ltd.　All　rights　reserved.