Study On Properties Of Ammonium Polyphosphate-based Intumescent Flame Retardant System For Polypropylene

In this paper, the envirommentally friendly intumescent flame retardant (IFR) was prepared with ammonium polyphosphate (APP) and pentaerythritol (PER) for Polypropylene (PP) flame retardant. The flame retardance properties, mechanical property and water resistant property of the composites were tested. Thermogravimetric (TG) analysis was used to analyze the thermal stability of the composites; APP was microencapsulated by HSO-MF resin, and Fourier transform infrared (FT-IR), energy dispersive spectrometer (EDS) and scanning electron microscopy (SEM) were used to identify the structure of HSO-MFAPP. The microencapsulated APP and PER was added to PP for flame retardant; maleic anhydride grafted polypropylene (PP-g-MAH) used as compatibilizer was added into the system of PP/APP/PER, the influences of the content of compatibilizer on the mechanical property, flame retardation, thermal stability and water resistance property were studied. The main work is as follow:1. Limiting oxygen index (LOI) and UL-94 vertical burning were used to investigate the effect of APP/PER ratio on the flame retardancy of PP/IFR blend test. The results showed that flame retardant of PP/IFR blend was optimal with the proportion of (22.5/7.5) APP/PER with 30wt%, LOI value is 31.5 and UL94 reached V-0 grade at 3.0mm thickness.. Thermogravimetric analysis was used to study the mechanism property and thermal stability of PP/IFR blend, the result shows that the suitable blowing agent/char former ratio of IFR to the flame retardance properties of PP/IFR system was important. On the other hand, the mechanical property, surface morphology of fracture and water resistance of PP/IFR blend were tested, results showed that mechanical property descend because of the poor compatibility between IFR and PP matrix.2. Microencapsulated ammonium polyphosphate (MCAPP) with a hydroxyl silicone oil-melamine-formaldehyde (HSO-MF) resin is prepared by in situ polymerization. HSO-MFAPP is characterized by Fourier transform infrared (FTIR), energy dispersive spectrometer (EDS) and scanning electron microscopy (SEM). The results show that the microencapsulation with HSO-MF resin leads to a decrease in water absorption. The flame retardant action and mechanism of HSO-MFAPP in polypropylene is studied using limiting oxygen index (LOI) and UL-94 test, and their thermal stability is evaluated by TG. The LOI value of the PP/HSO-MFAPP composite is 25.5%, whereas the corresponding value of the PP/APP composite is only 19.0%. The water resistance of PP/HSO-MFAPP or PP/HSO-MFAPP/PER composites is also studied, the water resistance of the PP/HSO-MFAPP or PP/HSO-MFAPP/PER composites is much better than the ones of the PP/APP/PER composites. Compared with PP/HSO-MFAPP, the LOI values of the PP/HSO-MFAPP/PER composites increase, and UL-94 rating of composites are V-0 grade. SEM also shows that APP after microencapsulation can improve the compatibility of IFR with PP matrix. Above results show that HSO-MFAPP/PER is a novel IFR system which has better water resistance and flame retardance.3. The grafted PP with maleic anhydride (PP-G-MAH) was used as compatibilizer for PP/IFR system. SEM analysis showed that the compatibility of IFR/PP/PP-G-MAH was good. PP-G-MAH can greatly increase mechanical properties of the composite, and good comprehensive property was obtained when the addition of PP-G-MAH is 5 wt%, the tensile strength was raised to 24.9MPa from 16.375MPa, the elongation at break was raised to 249% from 87.27%, but the impact strength was decreased with increasing of the content of PP-G-MAH. The UL-94 rating reached to V-0(3.0mm) grade. The water resistance of the PP/IFR/PP-G-MAH composites is much better than the ones of the PP/APP/PER composites.