Preparation Of Polyaluminosiloxane Flame Retardant And Its Application In PC

With the development of modern science and technology, the polymer materials are widely used in various industries. The polycarbonate (PC), as a major kind of polymers has increasingly applications in those industries because of its superior properties such as good transparency, strong mechanical strength, good heat resistance, good anti-ultraviolet radiation and electrical insulation features. With the growing demand for the PC in the filed of electron, electric, building, automobile and so on, the requirements of its flame retardant property, comprehensive performance and environmentally-friendly features become higher and higher. It is highly needed to develop an efficient halogen-free flame retardant for fire-retardant treatment of PC to meet the requirements in the related fields. In this research we use co-hydrolysis condensation to prepare environmentally friendly halogen-free polyaluminosiloxane flame retardants, and apply it to the PC for its fire-retardant treatments. The research focus on the following three aspects:the preparation of the polyaluminosiloxane and the measuring of its flame retardant properties; the impacts on PC physical properties when the polyaluminosiloxane is added into the PC; the effects of the nano-SiO2on properties of the PC/polyaluminosiloxane.Novel polyaluminosiloxane flame retardants were synthesized through co-hydrolysis condensation reaction using diphenyldimethoxysilicone (PTMS), dimethyldimethoxysilane (DMPS) and aluminum isopropoxide as the raw materials. The flame retardant action of polyaluminosiloxane on PC was analyzed by limiting oxygen index (LOI) method and the cone calorimeter. The presence of the polyaluminosiloxane can significantly improve LOI of PC and the structure of polyaluminosiloxane affects its flame retardancy greaterly. It is found that when the Ph/Me ratio is6:4, and the R/Si is1:2in the branched chain, the polyaluminosiloxane reaches its highest flame retardancy. Adding5%of this polyaluminosiloxane into the PC, the LOI of the PC increased from25.5%to30.4%. The presence of the polyaluminosiloxane in the PC can reduce PC's maximum thermal degradation rate, and increase its800℃carbon residue significantly. The800℃carbon residue of PC/polyaluminosiloxane system is30-45%higher than that of the pure PC, showing that the polyaluminosiloxane in PC reduced the degradation rate of the blends, and promoted the formation of the carbon layers, especially for the polyaluminosiloxane with1.2Si-O ratio in its branched chain. In the combustion process, polyaluminosiloxane will migrate to the PC surface, and PC degradation product interaction occurs, causing crosslinking structure. Si and Al accumulate in the material surface and form insulation carbon layer which is rich in Si,Al. When it is complete combustion, flame retardant PC forms a uniform, dense carbon layer, which acts as good insulating protection layer effects to inhibite material further degradation, effectively prevent the flammable gas produced and transfer to the combustion zone. Thereby it effectively improves the flame retardancy of PC. The cone calorimeter test results show that adding polyaluminosiloxane flame retardant in PC can prolong PC ignition time, effectively reduce smoke, heat and CO, CO2and other harmful gases generating in the burning process. Besides, it significantly improves the fire performance index, mitigates the whole combustion process, ensure the timely transmission of heat to the external environment, and reduce fire hazard.The tensile strength of the polyaluminosiloxane flame retardant PC (5WT%polyaluminosiloxane) is55.5-58.6MPa, while the tensile strength of the pure PC is55MPa. The presence of the polyaluminosiloxane improved the tensile strength of the PC. The flexural strength and impact strength of the pure PC are86MPa and16KJ/m2respectively, and the flexural strength of the PC/polyaluminosiloxane system is84MPa-89MPa. The effect of polyaluminosiloxane on the flexural strength of the PC is slight. The impact strength of the polyaluminumsiloxane retardant PC is15%to30%higher then that of the pure PC. Thus, on the whole, the effect of the polyaluminosiloxane on mechanical properties of the PC is not reduced but increased.In order to obtain flame retardant PC materials with more excellent flame retardant performance and comprehensive performance, a high performance flame retardant was screened out from the prepared polyaluminumsiloxanes. The polyaluminumsiloxane was then mixed with SiO2nanoparticles and PC to prepare the PC blends. The flame retardancy and the mechanical properties of these blends were investigated. The results show that the presence of the SiO2nanoparticles in the PC/polyaluminosiloxane has a little effect on its LOI value. However, the presence of the SiO2can reduce the heat release rate, and then reduces the fire hazard of the PC/polyaluminosiloxane. When increasing the SiO2content, the mechanical properties of flame-retardant PC material is firstly increased and then drop, adding an appropriate amount of nano-SiO2can improve obviously the tensile strength and impact strength of PC/polyaluminosiloxane flame retardant material. The nano-SiO2has a more significant influence on the impact strength of the PC/polyaluminumsiloxane. When the content of SiO2is1WT%, the influence reaches to the maximum value, and the impact strength is increased by48%than PC/polyaluminosiloxane without SiO2.