Preparation of Polyamide 6/Silica Modified Melamine Cyanurate Non-Halogen Flame Retardant Nanocomposites by In Situ Polymerization

Polyamide 6 (PA 6)/silica modified melamine cyanurate (mMCA) nanocomposites were prepared by in situ polymerization. When compared with MCA traditional preparation method, this method was found to be environmentally friendly, with no application of large amount of water and discharged waste water. The resultant materials were characterized by FTIR spectrometer, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analyzer (TGA), limiting oxygen index (LOI) instrument, horizontal and vertical burning tester, cone calorimeter and electronic universal testing instrument. The MCA could be modified by silica sol in molten caprolactam medium and mMCA particles were nanosized, with decreased thermal stability of PA 6 nanocomposites, and flame retardant property could reach UL 94 V-0 rating. With increase in the mMCA content, the LOI of PA 6 nanocomposites increased firstly and then decreased, and the maximum value was 35. With mMCA content increasing, both the total heat released (THR) and time of ignition (TTI) also increased. The peak heat release rate (PHRR) decreased, while tensile strength, flexural strength and modulus of PA 6/mMCA nanocomposites firstly increased and then decreased, with izod notched impact strength decreasing gradually. The tensile strength, flexural strength and modulus increased by 3%, 14.3% and 23.9% respectively. The properties of MCA were improved after modification and both the flame retardant and mechanical properties of PA 6 were also improved in the presence of mMCA.