Microstructural analysis and nonlinear optical properties of PP/PA6/Clay composites: a comparative study with and without compatibilizer

Ternary polypropylene/polyamide6/organoclay composites were successfully synthesized through a melt-mixing process, with and without a compatibilizer. The chemical-bond, structural, and morphological characteristics of composites were thoroughly investigated utilizing Fourier-transform infrared spectroscopy, wide-angle X-ray diffraction, and scanning electron microscopy analyses. The morphological investigations showed that the addition of a compatibilizer to the composite leads to a reduction in the size of the dispersed PA6/clay domains and a decrease in the distance between them due to the formation of a PP-g-PA copolymer at the interface, which improves compatibility between the PP and PA6 phases. Furthermore, the differential scanning calorimetry technique was employed to assess the crystallization and thermal action of the composites. The results revealed that the addition of a compatibilizer resulted in a slight increase in the crystallization temperature of PP and a reduction in the overall crystallinity of the composite, attributed to the compatibilizer’s interaction with both the clay and PA6/clay islands, limiting PP chain mobility and hindering crystallization. The band gap energies were determined in a range of 4.17–4.34 eV by diffuse reflectance spectroscopy and utilizing the Tauc method. Notably, this study marks the first instance of exploring the nonlinear optical properties of these composites. This was achieved by employing Z-scan technique by subjecting the samples to a continuous-wave Nd:YAG laser functioning at a wavelength of 532 nm. A positive nonlinearity of the order of 10^–8 cm²W⁻¹ was observed across all samples studied. Particularly noteworthy was the significant enhancement in nonlinear refractive index and absorption coefficients for polypropylene/polyamide6/organoclay ternary composites upon the addition of the compatibilizer. These findings strongly indicate the potential of these composites for applications in nonlinear optical devices and technologies.