Study On Synthesis And Characterization Of Spirocyclic Aromatic Phosphate Flame Retardants And Their Application In Polyolefin

As important commodity plastics, polyolefins, such as polyethylene(PE) and polypropylene(PP), have good chemical stability and good electricity insulation and are widely applied in the fields of automobile industry, electronic industry, communication equipments and packaging productions. However, polyolefin materials become very dangerous materials in fire due to their flammability. Flame retardants can make them delay ignition time and restrain fire spread, therefore people' lives is saved and the property is protected.Halogenated flame retardants is a kind of flame retardants that is used earlier and has good flame retardancy for polyolefin. However, the production and research of halogenated flame retardants were infinitely impacted because halogenated flame retardants produce dark smoke and release toxic gases, such as hydrogen halide and dioxins, during burning and the European Parliament and the Council legislated the RollS Directive to restrict of the use of certain hazardous substances such as PBB and PBDE in electrical and electronic equipment from 1 July 2006. It is an urgent task to look for the substitute of halogenated flame retardant for the industries of the production and research of flame retardants. The spirocyclic phosphate is a novel containing phosphorus flame retardant, which has been emphasized on their preparation and application.In this dissertation, 12 compounds of spirocyclic phosphates were designed and synthesized, and their structures were characterized by melt point, FTIR,¹HNMR, etc, and the thermal degradation behaviors of the flame retardants were analyzed by TG/DTG technique. Some of the flame retardants synthesized were applied in linear low density polyethylene (LLDPE), PC-modified high density polyethylene (HDPE) and PC-modified PP to obtain flame retarded materials, and the flame retardancy and mechanical properties were determined.Firstly, the intermediate of spirocyclic phosphates, 3,9-dichloro-2,4,8,10- tetraoxa-3,9- diphosphasprio[5.5]undecane-3,9-dioxide (SPDPC), was synthesized by using POCl₃ and pentaerythritol as raw materials, and the mole ratio of POCl₃ to pentaerythritol is 1:2.3. The synthetic reaction was kept at 80℃for 6 h in the organic solvent. The intermediate is a white and sandy crystal, and its yield reached 80%.Six flame retardant compounds, such as spirocyclic diphenol phosphate, spirocyclic dimethyphenol phosphate, spirocyclic diphenylamine phosphate, etc, were synthesized using SPDPC as the intermediate and water as a solvent. In the their synthetic reactions, the mole ratio of SPDPC to phenol was 1:2.2, pH value was controlled to be 8～9, the reactive temperature to be 5～10℃, and the reactive time to be 4～6 h. Then, by filtrating and washing, the white powder was abtained with 75～93% yield.Using SPDPC as the intermediate, flame retardant oligomers of spirocyclic p-benzenediol phosphates, spirocyclic m-benzenediol phosphates, spirocyclic bisphenol A phosphates, spirocyclic 1,4-diaminobenzene phosphates and spirocyclic melamine phosphates were synthesized by the methods of non-solvent and organic solvent. Their structures were identified by the melt point, FTIR and ¹HNMR, and the polymeriazation degrees of the oligomers was tested by the end analysis.The thermal degradation behavior of 12 synthesized flame retardant compounds were analysed by TG/DTG. The experimental results show that the thermal degradation temperature is 262℃at 5% weight loss for SPDPC, and the temperature of the weight loss peak is 303℃. The char residue of SPDPC is about 30% at 700℃. For six spirocyclic aryl phosphates, the thermal degradation temperature at 5% weight loss is between 320～360℃, the temperature of the weight loss peak is between 380～420℃, and the char residue of SPDPC is about 20～30% at 700℃. For five spirocyclic aryl phosphate oligomers, the thermal degradation temperature at 5% weight loss is between 266～336℃, the temperature of the weight loss peak is between 360～420℃, and the char residue of SPDPC is about 26～50% at 700℃.Using SPDPC as the flame retardant to treat LLDPE. When SPDPC addition was 30%, the LOI of LLDPE reached 21.3%, the tensile strength the flexual strength and impact strength were 14.6MPa, 23.6MPa and 5.1kJ/m² respectively. When the addition of spirocyclic melamine phosphate was 30%, the LOI of LLDPE was 26.2%, the tensile strength and the impact strength of LLDPE were 10.2MPa and 6.0kJ/m₂ respectively.Polymer blends of PC-HDPE and PC-PP were treated with spirocyclic diphenol phosphate, melamine phosphate(MP) and melamine (MA) to obtain flame retarded polymer blends. When the flame retardant was added 30% in the polymer blend and the weight ratio of spirocyclic diphenol phosphate to melamine phosphate(MP) was 7:3, the LOI of PC-HDPE reached 26.2%, the tensile strength, the flexual strength and the impact strength of flame retarded PC-HDPE were 18.0MPa, 26.5MPa and 9.1kJ/m₂ respectively. When the flame retardant was added 30% and the weightratio of spirocyclic diphenol phosphate to melamine (MA) was 1:1, the LOI of PC-PP reached to 8%, the tensile strength, the flexual strength and the impact strength of flame retarded PC-PP were 23.3MPa, 37.4MPa and 5.8kJ/m₂ respectively.Spirocyclic phosphate, as a kind of phosphorus containing intumescent flame retardants, can achieved better time retardancy in polyolefin when it is used with nitrogen containing compounds together.