Influence of ammonium polyphosphate microencapsulation on flame retardancy, thermal degradation and crystal structure of polypropylene composite

Microencapsulated ammonium polyphosphate (EPAPP) with shell of epoxy resin (EP) is prepared by in situ polymerization. EP is hydrophobic, so EPAPP has better water resistance and compatibility in polypropylene (PP) composite compared with ammonium polyphosphate (APP). Due to the reaction between APP and EP under heating, EPAPP can form a residue char with good thermal stability which prevents underlying materials from further destruction during a fire. Because of the interaction and alignment of the PP polymer chains at the surface of additives, microencapsulation affects the crystal structure and spherulitic morphology of PP composite remarkably. PP/EPAPP did not show characteristic peaks for β-form crystal, while APP could act as an effective β-nucleating agent in PP.