Novel Melt-Processable Nanocomposites Based on Isotactic Polypropylene and Carbon Nitride: Morphology, Crystallization, and Dynamic Mechanical Properties

Light element-based materials like spherical carbon nitride (C3N4) particles were melt-mixed at different concentrations with isotactic polypropylene to produce new nanocomposites. The iPP/C3N4 nanocomposites were characterized with differential scanning calorimetry (DSC), time-resolved synchrotron X-ray scattering experiments, and dynamic mechanical analysis (DMA). On the basis of the DSC experimental and theoretical analyses, the study of the dynamic crystallization kinetics provides a picture describing the physicochemical transformation of iPP molecules from the non-ordered state to the ordered state. The addition of C3N4 induces an increase of the crystallization rate and crystallinity of the polymer matrix, without variation of the crystalline structure of iPP. In the same way, the results of the nucleation activity confirmed the nucleating effect of C3N4 on the iPP crystallization. However, the addition of C3N4 causes an alteration of the effective energy barrier of the crystal growth process of iPP. The DMA studies revealed the reinforcing effect of the C3N4 on the mechanical performance of iPP with an increase in the storage modulus of around 32%. Moreover, the heat deflection temperature of iPP increased considerably, whereas the damping property was found to decrease because the C3N4 acted as barriers to the free movement of the iPP macromolecular chain.