Enhanced flame retardancy of natural rubber composite with addition of microencapsulated ammonium polyphosphate and MCM-41 fillers

Microencapsulated ammonium polyphosphate with melamine-formaldehyde resin (MCMF-APP) prepared by in situ polymerization and characterized by FTIR showed decreased water solubility and particle size in comparison to bare ammonium polyphosphate. APP was used as additive to natural rubber (NR) together with mesoporous silica MCM-41 as a synergistic agent to form intumescent flame retardant composite in this study. The flame retardancies of NR/APP, NR/MCMF-APP and NR/MCMF-APP/MCM-41 composites were studied using limiting oxygen index (LOI) and UL-94 test, and their thermal stability was evaluated by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) as well as physico-mechanical properties. The results indicated that the LOI value of NR/MCMF-APP composite was higher than those of NR/APP composite and NR. Addition of MCM-41 into NR/MCMF-APP composite further increased the LOI values and also increased the UL-94 ratings of most ternary composites to V-0 due to a synergistic effect between MCM-41 and MCMF-APP in NR composites. As the results showed, the thermal stability and flame retardancy of NR were enhanced. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.