Crystallization in J-1 polymer/carbon-fibre composites: bulk and interface processes

The process of crystallization, during isothermal treatments from the melt, of a composite of a J-1 polymer (a polyamide homopolymer produced by Du Pont) containing a single carbon fibre was studied. Two main crystalline morphologies develop in the polymer, depending on the temperature. This was directly observed during the treatment of the sample in a hot-stage chamber placed under a light microscope, and confirmed by both X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses. Moreover, a transcrystalline layer grows at the interface with the carbon fibre. The kinetics of bulk and interface crystallization were evaluated and compared by measuring, at different temperatures, the radii of crystals and the thickness of the transcrystalline layer with time. Moreover, bulk crystallization kinetics, measured by the depolarization of the light passing through the polymer sample during the isothermal treatment, indicated the apparent presence of two regimes of bulk crystallization.