Flame-retardant and thermal properties of highly efficient water-resistant intumescent flame-retardant polypropylene composites

The more efficient and hydrophobic modificated ammonium polyphosphate (M-APP) and charring agent (M-CA) were prepared based on sol-gel method, and they were used in the preparation of water-resistant and flame-retardant polypropylene (PP) composites. The results showed that the contact angles of M-APP and M-CA were 135.11 degrees and 137.89 degrees, respectively. The flame-retardant and thermal properties of the PP composites were also studied. The results showed that the flame retardancy of PP loaded with 30 mass% intumescent flame retardant (M-APP/M-CA = 3:1) was significantly increased. The limiting oxygen index (LOI) reached 36.8% and passed UL-94 V-0. The peak heat release rate and total heat release of the PP composite decreased from 1011.77 to 134.43 kW.m(-2) and 100.58 to 6.86 MJ.m(-2), respectively. The peak smoke production rate and total smoke release decreased from 0.13 to 0.0056 m(2).s(-1) and 1453.09 to 74.82 m(2).m(-2). The PP composite with M-APP/M-CA = 3:1 also exhibited excellent water resistance, and it could still reach UL-94 V-0 after soaking in 70 celcius water for 168 h.