Synthesis of star-shaped polyamide-6/SiO2 nanocomposites by in situ anionic polymerization through reactive extrusion

The effects of an epsilon-caprolactam (CL) modified nanosilica (MNS) component on thermal properties, morphology and rheological behavior of PA6/SiO2 nanocomposites were investigated. Star-shaped PA6/SiO2 nanocomposites were synthesized through a two-step in situ anionic ring-opening polymerization (AROP) of CL monomer by hexamethylene diisocyanate (HDI) linking the nanoparticles and CL in a reactive melt blending. The star-shaped structure was observed by field emission scanning electron microscope (FESEM) and elemental mapping. Moreover, the study on chemical structure of the samples was carried out by Fourier transform infrared (FTIR), energy-dispersive X-ray spectroscopy (EDX) and carbon nuclear magnetic resonance (C-13 NMR) spectroscopy. Incorporating MNS increased gamma-crystal and arm numbers of the star-shaped structure. Thermal degradation increased in the star-shaped samples due to the effects of MNS and molecular weight (MW). However increasing the number of arms was effective in increasing the temperature of degradation. In addition, the crossover of storage modulus (GMODIFIER LETTER PRIME) and loss modulus (G '') shifted to higher frequencies in the low- and lower frequencies in the multi-arms star-shaped samples. Shear viscosity and glass transition temperature (T-g) of the multi-arms samples with maximum MNS loading were lower than those of other samples. Furthermore, dispersity, and their MWs were higher than those of other samples. Therefore, the resulting multi-arms star-shaped nanocomposites may be desirable for industrial productions in absence of solvents and lowering cost and energy rather than linear PA6.

Automated summary

The effects of MNS on the thermal properties, morphology, and rheological behavior of PA6/SiO2 nanocomposites were investigated. It was found that MNS increased the crystallinity and arm number of the star-shaped structure, as well as enhanced thermal degradation and degradation temperature. The crossover point of storage modulus and loss modulus shifted in the multi-arms star-shaped samples. The multi-arms samples with maximum MNS loading showed lower shear viscosity and glass transition temperature than other samples.