Synergism between hydrotalcite and silicate-modified expandable graphite on ethylene vinyl acetate copolymer combustion behavior

Influence of independent Mg-Al-layered double hydroxide (LDH), silicate modified expandable graphite (EG), mixture of LDH and EG at various ratios on ethylene vinyl acetate copolymer (EVA) combustion behavior and thermal stability was detected in sequence through the limiting oxygen index (LOI), vertical combustion (UL-94) level, microscale combustion calorimeter (MCC) tests and thermal gravimetric/differential thermal gravimetric (TG/DTG) analysis. Results show that the 30 wt % LDH can improve the LOI of 70EVA/30LDH to 27.0%, but the combustion accompanies with serious melt-dropping. While, the same amount of the EG can increase the LOI, UL-94 level to 28.5%, V-0 respectively. However, the combination of LDH and EG can further enhance the 70EVA/20LDH/10EG flame retardancy, it presents the LOI of 29.7%, UL-94 level of V-0, and total heat release of 29.5 kJ g(-1). The excellent flame retardancy is attributed to its compact residue. Compared with residue mass, the residue compactness plays a more important role in improving flame retardancy. (C) 2016 Wiley Periodicals, Inc.