Study On Microencapsulation Of Ammonium Polyphosphate And Synthesis Of Efficient Char-forming Agent In Intumescent Flame Retardant Polypropylene System

Polypropylene(PP) is a widely used thermoplastic resin, but the disadvantage of PP can not be ignored:PP is extremely flammable and always along with serious melt drops off phenomenon in the air. In certain fields where PP is of high flame retardance required, intumescent flame retardant is a hot topic recently due to its environmental friendly, low smoke and non-toxic characterics. But the traditional IFR system(APP/PER/MEL) possesses some drawbacks such as high addition, low flame retardance efficiency and poor compatibility. Therefore this thesis mainly focuses on studying a new type IFR system.This work can be divided into three parts:modification of acid source, synthesis of a char-forming agent and synergistic effect of hypophosphite. Firstly, tris(2-hydroxyethyl) isocyanurate (THEIC) is used as a modifier for melamine formaldehyde resin, followed by microencapsulation of ammonium polyphosphate. The coated ammonium polyphosphate has good water resistance and flame retardancy, while the solubility of MFT-APP is decreased 45.5% compared with APP, and with 30% addition of MFT-APP the polypropylene can successfully passed the vertically combustion UL-94 V-0 level test, the oxygen index is 32%. Secondly, a high efficiency and water-resistantce char-forming agent (TE-4) is successfully synthesized by the esterificated reaction between THEIC and ethylenediaminetetraacetic acid (EDTA). When the ratio of ammonium polyphosphate (APP) to TE-4 is 2 and the total addition is 25%, the flame retardant materials can succseefully pass the vertical burning UL-94 V-0 level test and the limiting oxygen index is 33%. Finally, two different typle hypophosphite (CaHP and AlHP) are adopted to synergist the IFR-PP system. It is found that there is different synergistic effect when same hypophosphite is used to synergist with different intumescent systems. What is more, there is also different synergistic effect between different metal hypophosphites in same IFR-PP system. These results are helpful for understanding the synergistic effect between hypophosphite and intumescent flame retardant system.