Tailoring the Localization of Carbon Nanotubes and Ammonium Polyphosphate in Linear Low-Density Polyethylene/Nylon-6 Blends for Optimizing Their Flame Retardancy

Abstract

Carbon nanotubes (CNTs) and ammonium polyphosphate (APP) was used to improve the flame retardancy of linear low-density polyethylene/nylon-6 (LLDPE/PA6) blends. It was observed that APP or CNTs tended to be dispersed in the PA6 phase of the blends when all components were melt-blended together. CNTs dispersed in the PA6 phase caused the decrease of flame retardancy. Different processing methods were used to tailor the localization of APP and CNTs in the blends. The results showed that the localization of CNTs or APP strongly influenced the flame retardancy of blends. APP-incorporated CNTs had antagonism in blends with APP localized in the LLDPE phase and CNTs in the PA6 or LLDPE phases. A synergism between APP and CNTs was exhibited only in blend with the localization of APP in the PA6 phase and CNTs in the LLDPE phase. SEM observation showed that the residual char layer in blends with poor flame retardancy was either discontinuous or continuous but porous. A continuous and compact-residue char layer was observed in blends with excellent flame retardancy. Different morphologies of the residual char layer could be attributed to the difference of residual char mass and network structure.