Study On The Preparation And Flame Retardancy Of Black Phosphorene-based Composite Materials

Polymeric materials are widely used in various fields,but they are extremely flammable and easy to cause fire.Therefore,we need to improve the flame retardant properties of materials to protect people's lives and property.The development of an excellent Non-toxic,non-polluting,less amount of addition and good compatibility with polymers is a breakthrough in the field of flame retardant.As a flame retardant,elemental phosphorus has the advantages of high efficiency,halogen-free,low toxicity,etc.However,due to the difficulty of nanometer,the red phosphorus used more often has some shortcomings such as poor compatibility with macromolecule and easy precipitation.In this paper,nano black phosphorus?BP?with 2D layered structure and large specific surface area has been introduced in the system,which has been applied through the strong interfacial interaction with polymer materials and form into stable and high-performing Nano black phosphorus/polymers.BP not only can significantly increase the flame retardant property,but also improve the mechanical performance through target design of the microstructure.Through a series of characterization,the capture and analysis of intermediate products and final products,the microstructure and reaction pathway of the materials.This project will lay the theoretical foundation and experimental basis of the development and application of BP based nano flame resistant materials.The main research contents are as follows:?1?BP was obtained by liquid phase method and added to WPU directly.A BP/WPU polyurethane composite polymer containing 0.2%?mass fraction?of BP was synthesized to prepare.The morphology of the black phosphorus in the waterborne polyurethane matrix was observed with a scanning electron microscope?SEM?,indicating that the black phosphorus was uniformly distributed in the WPU.Thermal analysis results show that black phosphorous could effectively inhibit the thermal degradation of WPU,and the heat flow rate decreased by 34.7%.Compared with pure WPU,the limit oxygen index?LOI?of black phospholene/water-based polyurethane composites increased by 2.6%,and the peak heat release rate?PHRR?decreased by10.3%.The results show that black phosphorous has good flame retardancy.?2?To solve the problem of mechanical property degradation after BP added WPU,black phosphonene/graphene?BP/G?composite was designed and prepared by the High-pressure Nano Homogenize Machine?HNHM?.BP/G composite material was added to waterborne polyurethane to form BP/G/WPU composite material with the addition amount of 3.55%.Through X-ray diffraction?XRD?and Raman spectrum analysis,it was found that a small number of p-c bonds formed in the two nanosheets.The structure,thermo-stability,flame retardant properties and mechanical performance of composites are analyzed by a series of tests.The structure characteration results showed that the BP/G composite material can distribute uniformly into the WPU.The addition of BP/G composites increased the residue of WPU from 0.96%to 5.64%,significantly inhibiting the thermal decomposition of WPU.Compared with WPU,the PHRR?235.4 kW/m2?and THR?51.68 MJ/m2?of BP/G/WPU decreased by 48.18%and 38.63%respectively.The mechanical analysis presents that the Young's modulus of the BP/G/WPU has an increase of 7 times more than the BP/WPU,which indicates that the introduce of graphene can effectively improve the mechanical properties of the single BP/WPU.TG-FTIR test of WPU and BP/WPU composite materials was carried out to analyze the gas composition produced by the thermal decomposition of the materials.In addition,the composition analysis of the combustion residue of CC was conducted to explore the elementary composition in the condensed phase.BP/WPU test results showed that with the temperature rising to about 240?,BP began to promote the decomposition of WPU and catalyze the formation of carbon layer.When the temperature reaches above420?,most BP begins to enter the gas phase to form phosphorous radicals,which causes the material to release more non-combustible gases to delaying combustion.P-C,P-O-C and P₂O₅ bonds were detected in CC residue,indicating that BP plays a catalytic role in carbon formation.?3?The LOI of BP and BP/G added to WPU couldn`t reach the level of refractory materials,so boron nitrite?BN?was introduced to improve the LOI value of materials.BP and BN was obtained by liquid phase method.WPU and these two flame retardants were used to prepare composite materials,the mass fraction of BP was 0.2%and the quality fraction of BN was 0.2%.The fracture morphology of BP/BN/WPU composites were observed by scanning electron microscopy?SEM?,and the results showed that the BP and BN were evenly dispersed in the matrix.TG analysis,LOI test and CC test were carried out to research the flame retardancy and synergistic effect of black phosphorous and boron nitride.The results show that the LOI of BP/BN/WPU reaches to 33.8%,the PHRR significantly decreases by 50.94%,After the CC test,the residue of BP/BN/WPU was about 10 times that of pure WPU.Therefore,BP and BN nanosheets can play a synergistic role in inhibiting fire risk and will be a promising synergistic flame retardant.BP/BN/WPU test results showed that Most of the BP enters into the gas phase,and a small amount of BP remains in the condensed phase to catalyze the polymer into carbon.BN mainly stays in the condensed phase to play the role of lamellar barrier,and the presence of P-C bond was detected,indicating that BN has the effect of catalytic carbonization.?4?BP-GO-BN ternary composite was formed by ultrasonic separation of black phosphorus,GO and boron nitride.BP-GO-BN were added to WPU to to further improve the dispersibility of flame retardant and the flame retardant property of composites.The structure,thermo-stability and flame retardant properties of composites are analyzed.Antifrictional Metel?AFM?results showed that BP-GO-BN formed a lamellar structure with a size of 200-500 nm and a thickness of 2-3 nm.The results of SEM show that BP-GO-BN composite can disperse evenly in WPU.The results of thermal analysis showed that the amount of carbon residue would increase with the addition of BP-GO-BN nanosheet under inert atmosphere.The CC test shows,The peak heat release rate of the WPU with the addition of bp-go-bn of 1.2%was48.49%lower than that of pure WPU,and THR was 47.02%lower than that of pure WPU.The residue increased greatly and formed large and dense blocks.BP-GO-BN ternary flame retardant has good dispersibility and flame retardant property.The test results of WPU/BP-GO-BN showed that as the temperature increased,GO began to decompose and convert into stable and self-crosslinked graphene after 50?,thus making residue more compact.At 240?,BP starts to transform into phosphoric anhydride,which promotes the formation of carbon layer.After 420?,BP mainly enters the gas phase and generates non-combustible gas to delay combustion.The BN will will stay in the condensed phase,which not only has the iris action,but also has the function of catalyzing the formation of char layer,further formation of compact char layer.BP also possesses the flame retardant mechanism of condensed phase and gas phase,which has the synergistic flame retardant effect after being compounded with other two-dimensional materials.This mechanism has certain theoretical guiding significance for the design of BP-based flame retardants.