Preparation Of Microencapsulated Ammonium Polyphosphate And Its Application In Flame Retarding Polypropylene

Polypropylene is extensively used in many fields, such as automobiles, housing, chemical industry, for its low price, ease-processing and low density. However, due to the flammability property, its applications have been severely restricted in many fields, such as electrical materials. Lots of efforts have been made to improve the flame-retardant properties of PP over the pass decades. Bromine-containing compounds can efficiently improve the flame retardancy(FR) of PP, but their use has been limited due to safety and environmental concerns. Therefore, the development of non-toxicity and smokeless, intumescent flame retardant (IFR) in which ammonium polyphosphate (APP) is the main composite, have become the trend of halogen-free flame retardant in the polypropylene system. However, their low flame retardant efficiency and poor thermal stability are still two drawbacks in comparison with bromine-containing flame retardants. microencapsulated ammonium polyphosphate (MAPP) with epoxy resin is prepared to improve the compatibility between intumescent flame retardants and polypropylene. Besides, In order to improve the efficiency of intumescent flame retardants, we introduced series of synergists into polypropylene, and studied intensely the synergistic mechanism of the synergists.The main contents are summarized as follows:Firstly, Microencapsulated ammonium polyphosphate (MAPP) with epoxy resin is prepared by in situ polymerization. The influence of the different process parameters such as the amount of capsule materials, the curing time and solidification fraction was investigated, when the capsule material addition amount was10%, and the addition the amount of curing agent for epoxy resin is15%, using40℃/h-70℃/h heating method, the MAPP is low solubility in water with good water resistance, the oxygen index test results are good, the formed carbon layer is more conducive to the flame retardant. Microencapsulation gives MAPP better resistance and flame retardance compared with APP in thermoplastic polypropylene.Secondly, The optimal mass ratio (3:1) of MAPP-PER in the intumescent flame retardant was found after systematically investigation of the flame retardant property via LOI, UL-94and tensile strength test. The mechanism of MAPP-PER was studied by TGA. The TGA result showed that Ea of polypropylene was improved from98.1KJ/mol to129.8KJ/mol. Finally, The effects of synergists on the flame retardant property of polypropylene were investigated. The optimal additions of the synergists were obtained via LOI and UL-94tests. According to the results of LOI and UL-94, the optimal addition (1.5wt%) of SrCO3, the LOI and UL-94could reach35.2%and V-0rating, respectively. The synergistic mechanism of SrCO3was investigated via TGA and FT-IR, which indicated that SrCO3could react with MAPP to form the crosslink structure, then the crosslink structure reacted with PER to form the crosslink, smooth and compact char layer.