Controllable Synthesis Of Zinc Borate And The Research Performance Of Its Flame Retardant

Zinc borate is a kind of widely used inorganic flame-retardant in industry. It has the following excellence that belongs to inorganic flame-retardant:the perfect thermal stability, no volatilization, no separating out and no toxicity. Otherwise, zinc borate promotes fume suppression and the expanding of char. While used with other kind of flame-retardants, its effect becomes better.In order to elevate the flame retardant performance of zinc borate in polymers, there are two methods. The first is reducing the granularity of zinc borate to the nano scale, which could increase the interface between zinc borate and polymers and make good use of the function of zinc borate. The second is the modifying the surface of zinc borate. Because of the poor compatibility between zinc borate and polymers, it is necessary to modify the surface of zinc borate. After that, it is possible to avoid the destroy of mechanical properties of zinc borate/polymers.In our research, we synthesized zinc borates using two ways. The first is that we had successfully synthesized the 2ZnO·3B2O3·3.5H2O using ZnO and H3BO3 as the stuffs. To get the pure nano 2ZnO·3B2O3·3.5H2O, the reacting conditions set as follows:the temperature should be higher than 85℃, and the molar ratio of boric acid and zinc oxide should be higher than 3:1, and the reaction time should be longer than 2h. The synthesized zinc borate displayed nanoflake morphology with particle size of around 100-200 nm, thicknesses less than 100 nm, and that there are some uniform mesopores in the particles and the diameter of the cavities is about 10 nm. To modify the surface of zinc borate, we used the oleic acid as the modifying agent. While the dosage of oleic acid was 2.0 wt.%, the water contact angle of zinc borate reached to 129°. The second synthesis method was that we use Na2B4O7·10H2O and Zn(NO3)2 as the reactants. By controlling the reacting conditions, we could get three kinds of zinc borates, that is,2ZnO·3B2O3·7H2O,3ZnO·3B2O3·5H2O and 2ZnO·3B2O3·3.5H2O.We also did some research about the synthesized zinc borate's flame retardant. We chose the hydrophobic zinc borate (2ZnO·3B2O3·3.5H2O) as the experiment object, which synthesized using ZnO and H3BO3 as the reactants and oleic acid as the modifying agent. Through solution mixed method, we mixed the hydrophobic zinc borate (2ZnO·3B2O3·3.5H2O) in PE, getting zinc borate/PE composites. To test the flame retardant of hydrophobic zinc borate, we mainly used TGA to research the thermal stability of zinc borate/PE composites, getting the general assessment about the flame retardant of zinc borates. The test results indicted that, when the dosage of hydrophobic zinc borate in PE reached 2.0 wt.%, the decomposition on-set temperature would elevate from 340℃to 408℃.