Preparation of APP with raffinate acid and its application to flame retardant PP
The byproduct raffinate acid generated by the wet-process phosphoric acid purification process is used as raw material to prepare flame retardant APP.The effects of material ratio,reaction time and reaction temperature on the product indexes are studied.The results show that the optimal reaction process of APP is as follows:Molar ratio of nitrogen and phosphorus is 4∶1,reaction temperature is>280-300℃,reaction time is 4 h.The obtained product indexes are as follows:Nitrogen content is 12.4%,P2O5 content is 53.2%,average degree of aggregation is 68,pH is 7.05,water solubility is 2.86 g.Then the APP is added to PP as an intumescent flame retardant(IFR)with melamine and pentaerythritol.The effect of IFR on PP flame retardancy is investigated,and the results show that compared to pure PP,when the addition amount of IFR is 30%,the maximum heat release rate and total heat release of PP/IFR are decreased by 68.1%and 20.7%respectively.It passes the UL-94 test with a V-0 rating,and the limit oxygen index(LOI)increases from 18.1%(for pure PP)to 29.5%.
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