Preparation And Application Of Brucite-Based Flame Retardants With Structural Synergy

Along with the process of halogen-free flame retardants, brucite/magnesium hydroxide has drawn great attentions due to its abundant raw materials, non-toxic and smoke suppressibility. However, its fatal disadvantages are the low flame retardant efficiency and high loading amount, leading to poor mechanical properties of polymer composites. Herein, a novel structural synergy strategy is proposed to remarkably improve the mechanical properties and flame retardancy of polymer composites by controlling and adjusting the hybrid structure of brucite and flame retardant synergists. To evaluate the improvement of different hybrid structures, we designed and synthesized a series of brucite hybrid flame retardants containing virous structures and compositions. And their application performance and mechanism were also investigated. The main points of this dissertation are as follows:(1) Magnesium hydroxide nanoneedles were synthesized directly from natural brucite via a facile and dissolution-free route in the presence of sulfosalicylic acid and polyethylene glycol (PEG, MW1000), and magnesium hydroxide nanopaltes were obtained under the same condition in the presence of polyethylene glyco only. The comparative experimental results verified that the nano-scaled magnesium hydroxide could highly enhance the tensile strength but fail to improve the elongation at break in the EVA matrix. Furthermore, the nano magnesium hydroxide, especially the needle-like one, could significantly increase the limiting oxygen index, but it still need60wt%loading amount to achieve UL94rating. The reason for this phenomenon is its fragile carbon layer.(2) A novel hybrid flame retardant consisting of a brucite core and a SiO2shell was synthesized by sol-gel method. The comparative experimental results verified that the brucite@SiO2hybrid structure could improve the mechanical properties to some extent and highly enhance the flame retardant behaviors in EVA matrix. With the same loading amount of50wt%, the EVA/brucite@SiO2composite could meet the requirements of the application performance.(3) A new composite flame retardant consisting of a brucite core and a fine zinc borate [Zn6O(OH)(BO3)3] hierarchical nanostructure shell was designed and synthesized via a facile gradual deposition route. The comparative experimental results verified that the brucite@Zn6O(OH)(BO3)3hybrid hierarchical structure could remarkably enhance the mechanical properties and flame retardant performance. With the same loading amount of45wt%, the EVA/brucite@Zn6O(OH)(BO3)3composite could achieve the requirements of the application performance.(4) A series of organic-inorganic hybrid flame retardants with controllable interfacial properties consisting of a brucite core and an amine polyphosphate shell was synthesized via a step grafting routes. The control experiments verified that the brucite@amine polyphosphate could obtain controllable mechanical properties in EVA polymer by adjusting the surface organic molecular structure. Meanwhile, it could extremely improve the flame retardant efficiency. With the same loading amount of40wt%, the EVA/brucite@amine polyphosphate composite could meet the requirements of the application performance.