Synthesis Of A Novel Phosphate Flame Retardant And Its Intumescent Flame Retardant Polypropylene

Many traditional halogen containing flame retardants are in a dilemma due to the strict requirement of less smoke and poison, this offers a good opportunity for the development of halogen-free phosphorus flame retardants. As a kind of important common plastic, polypropylene(PP) has good chemical stability and good electricity insulation. However, it is easy to burn due to its lower oxygen index, only 17-19%. Synthesis of novel phosphate flame retardant and their intumescent flame retardant polypropylene has become the world's research focus of flame retardant polypropylene.In this paper, the first compound of 2-chloro-2-oxo-5,5-dimethyl-1,3,2-dioxaphosphorinane (DOPC) was synthesized on basis of the materals of neopentyl glycol and phosphorus oxychloride. Then DOPC respond with pentaerythritol to obtain a novel halogen-free phosphorus flame retardant, tetra(5,5-dimethyl-1,3-dioxaphosphorinanyl-2-oxy) neopentane (DOPNP). And the structure of DOPNP was characterized by FT-IR,1H NMR, 31P NMR and TGA. The thermogravimetric analysis (TGA) results demonstrate that DOPNP showed a good char-forming ability. Its initial decomposition temperature was 236.4℃based on 1% mass loss, and its char residue was 41.2 wt% at 600℃, and 22.9 wt% at 800℃, respectively.The flame retardancy of a novel intumescent flame-retardant (IFR) system consisted of DOPNP, APP, melamine polyphosphate (MPP) and synergistic agent (4A zeolite) for PP were investigated. Through a series of flame-retardant compound test, the optimal flame retardant formulation was DOPNP/APP/MPP=1/10/5. Then the intumescent flame retardant(IFR) with the best ratio was added for PP to study The flame retardancy properties of a novel intumescent flame-retardant polypropylene system (IFR-PP). The results of comparative flame-retardant test demonstrate that DOPNP effectively raised LOI value and UL-94 level of IFR-PP. When the loading of IFR was 30 wt%, LOI of IFR-PP reached 31.3%, and it passed UL-94 V-0.Thermal degradation behavior and combustion behavior of the IFR-PP composites were characterized by thermogravimetric analysis (TGA) and cone calorimeter (CONE), while the morphological structures of char layer was observed by scanning electronic microscopy (SEM). The thermogravimetric analysis (TGA) results demonstrate that DOPNP-APP-MPP showed a good char-forming ability. Its initial decomposition temperature was 216℃based on 1% mass loss, and its char residue was 55.1 wt% at 600℃, and 47.5 wt% at 800℃, respectively. CONE results show that DOPNP-APP-MPP could effectively decrease the heat release rate peak(HRR),the total heat release(THR),the smoke production rate(SPR),the total smoke production(TSP) and CO production (COP) of PP. Mechanical properties and SEM tests show that DOPNP showed better compatibility of IFR and PP matrix and a continuous and compact char layer formed during LOI tests.