Study On The Preparation Of Encapsulated Red Phosphorus And Its Flame Retardant Performance In The Wood Plastic Composites

The inorganic encapsulated red phosphorus (IERP) and organic-inorganic double encapsulated red phosphorus (OIERP) had been prepared by precipitation method with magnesium hydroxide and polyethylene (PE) as capsule wall, the red phosphorus (RP) as the capsule core. The optimum synthetic process conditions of inorganic encapsulated red phosphorus were determined through the optimization of synthesis process parameters. Applying IERP to wood plastic composite (WPC), and investigating the influence on the flame retardant properties and mechanical properties of wood plastic composites by two kinds of coated red phosphorus. The research, by means of thermal analysis, discussed the thermal decomposition properties of composite materials. By means of single heating rate method, the activation energy of material was calculated. Furthermore, the flame retardant mechanism of encapsulated red phosphorus flame retardant was researched based on the change rule of activation energy after the adding of flame-retardants.In this dissertation, the main research conclusions are as follows:(1) The IERP was prepared by the liquid phase precipitation reaction. Through single-factor and orthogonal experiment, the results showed that the synthesis technological conditions of IERP were optimized with reaction temperature of 80 ℃, the stirring speed of 300 r/min, the concentration of sodium hydroxide solution of 1mol/1 and magnesium hydroxide proportion of 30% in IERP.(2) The performance of IERP and OIERP were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), thermo gravimetric analysis (TG) and Fourier transform infrared spectrometer (FT-IR). The results showed that red phosphorus was encapsulated well by magnesium hydroxide and PE with the shallow of its color. The cladding rate of IERP and OIERP were 81.5% and 91.4%, respectively. Meanwhile, the moisture absorption rate of IERP and OIERP were 2.5% and 1.4% and the oxidation resistance of IERP and OIERP were 0.56 mg/(g·h) and 0.16 mg/(g·h), respectively. Compared with the moisture absorption rate of 10.6% and the oxidation resistance of 8.24 mg/(g·h) of red phosphorus, the performance of IERP and OIERP were obviously improved. The weight loss ratio of IERP was significantly higher than that of red phosphorus within the temperature range from 340 to 540 ℃. In addition, the carbon residue levels of IERP were around 34% higher than that of red phosphorus.(3) Two encapsulated red phosphorus flame retardants were applied in WPC. Through the oxygen index and vertical combustion performance test, the results showed that the oxygen index of WPC increased with rising addition of encapsulated red phosphorus. The composite materials could achieve UL94 V-0 level, with the addition of 8% IERP and 10% OIERP, respectively. These indicated that magnesium hydroxide and red phosphorus played a very good flame retardant effect, and could have obvious synergistic effect. However, the tensile strength, elongation at break and bending strength of composite materials reduced with the increasing encapsulated red phosphorus amount.(4) The thermal degradation process of WPC was composed of three steps:the first step (220-380 ℃), the second step (420-530 ℃) and the third step (630-700 ℃). The corresponding activation energy of the former two stages in the process of thermal decomposition was 37.3kJ/mol and 69.8kJ/mol, respectively. The activation energy of the former two stages of WPC was 37.5kJ/mol and 53.4kJ/mol while the IERP added in. The addition of flame retardant made the activation energy of WPCs reduce in the second stage of thermal degradation.