Preparation Of Zinc Hydroxystannate-Base Nanohybrid Flame Retardantr And Its Effect On The Flame Retardancy Of Polymer

Zinc hydroxystannate(ZnSn(OH)6), a class of perovskite-structured hydroxide material, is well-documented as efficient nontoxic flame retardants and smoke suppressants and therefore it is also considered as one of the most promising functional materials to solve the energy and environmental problems. In this work, because of the agglomeration and poor dispersion of zinc hydroxystannate(ZHS)nanoparticles, we selected a novel organic-inorganic hybrid flame retardant containing phosphorus and silicon(denoted as DOPO-VTS) and to modify ZHS nanoparticles and prepared DOPO-VTS-ZHS nanoparticles. On the one hand, surface modifier could reduce the agglomeration of ZHS nanoparticles and improve the dispersibility properties of ZHS nanoparticles in polymer matrix. On the other hand, the synergistic effect between modifier and ZHS nanoparticles could improve the flame retardant properties of ZHS nanoparticles in polymer matrix. Moreover, we used ZHS nanoparticles to decorate the graphene oxide(GO) nanosheets to prepare a new ZHS/GO nanohybrids flame retardant additive for the poor dispersion of ZHS nanoparticles in polymer matrix. On the one hand, ZHS nanoparticles could improve the compatibility properties and mechanical properties of polymer because that the oxygen containing functional groups on the surface of the GO interact with matrix formation to form a network structure; on the other hand, GO unique two-dimensional layered structure promotes the formation of continuous and compact carbon layer, and the specific surface area can be adsorption and hinder the transfer of heat and gas. Furthermore, the synergistic effect between ZHS nanoparticles and GO could improve the flame retardant properties of polymer. The structure and morphology of DOPO-VTS-ZHS and ZHS/GO were characterized by X-ray diffract(XRD), Fourier transform infrared spectrometry(FT-IR), Transmission electron microscopy(TEM) and so on. The flame retardant, smoke suppression and mechanical properties of polymer filled with DOPO-VTS-ZHS and ZHS/GO were evaluated by limited oxygen index(LOI), cone calorimetry, tensile strength and so on. Moreover, the flame retardant mechanism was determined by SEM and XPS analysis of the morphology and structure of the carbon layer after combustion. These main research results and contents were as follows.1. Preparation of DOPO-VTS-ZHS nanoparticles and investigation of its effect on mechanical properties and flame retardancy of polymerzinc hydroxystannate(ZHS) nanoparticles surface-modified with DOPO-VTS were synthesized by surface modification technology. The structure and morphology characterization results of DOPO-VTS-ZHS nanoparticles showed that surface modification by DOPO-VTS does not change the crystal structure of ZHS nanoparticles and DOPO-VTS helps to reduce the agglomeration of ZHS nanoparticles.The results showed that: First, thermal gravimetric data showed three kinds of complexes ultimate residual carbon content increased with the amount of additives increasing. Pure PVC carbon residue content was 0.63%, when 7 wt. % three kinds of additives were added into PVC, the ultimate residual carbon content of ZHS/PVC, DOPO-VTS/PVC and SA-ZHS/PVC were 0.82%, 0.75%, 1.36% respectively.Secondly, LOI of three types of nanocomposites also had the same trend as carbon residue content. When the three kinds of additives were added, LOI of ZHS/PVC, DOPO-VTS/PVC and DOPO-VTS-ZHS/PVC would increase from 25.8 of pure PVC to 28.9, 26.6 and 30.2, respectively. Thirdly, the cone calorimeter result revealed that the three kind of flame retardants could obviously reduce the peak heat release rate(pHRR), the total heat release(THR) and smoke products of PVC. Among them, DOPO-VTS-ZHS had the most significant effect. At last, the tensile strength test showed that DOPO-VTS play a favorable role in improving the compatibility between ZHS nanoparticles and PVC.Moreover, the results of DOPO-VTS-ZHS can also improve the flame retardant and mechanical properties of EP, and the SEM analysis showed that the char layer of DOPO-VTS-ZHS/EP after combustion was also more dense and continuous.2. Synthesis of ZHS/GO nanohybrids and their synergistic reinforcement on reducing fire hazards of flexible poly(vinyl chloride)Zinc hydroxystannate(ZHS) nanoparticles decorated graphene oxide(GO) nanosheets were successfully prepared by a simple solution method. The structure and morphology characterization results of ZHS/GO nanohybrids showed that ZHS nanoparticles are integrated with the GO nanosheets utilizing an electrostatic interaction. Subsequently, as-prepared ZHS/GO was introduced into flexible poly(vinyl chloride)(PVC) and fire hazard behaviors and mechanical properties of PVC nanocomposites were investigated. Compared to neat PVC, thermogravimetric analysis exhibited that the addition of ZHS/GO nanocomposites into PVC matrix led to an improvement of the charring amount and a decrease in the valueof derivative thermogravimetric peak. Moreover, the incorporation of 5 wt. % ZHS/GO imparted excellent flame retardancy to flexible PVC, as shown by increased limiting oxygen index value, reduced peak heat release rate and total heat release value tested by an oxygen index meter and a cone calorimeter,respectively. In addition, the addition of ZHS/GO nanocomposites dramatically decreased the smoke products of PVC. More importantly, ZHS/GO can increase the tensile strength of PVC matrix, which implies that GO favors to improve the compatibility between ZHS and flexible PVC matrix.