The Preparation、Modification Of The Mg-Al Hydrotalcite Flame Retardant And Its Application On Polypropylene

Hydrotalcite flame retardants are new inorganic flame retardants with halogen-free and friend environment, which widely applied in the field of polymeric materials. However, it is hard for the large scale commercial application of the retardants due to their low efficiency, poor dispersion and compatibility. It has recently become a hotspot to solve these problems. The hydrotalcite retardant with ultra-fine grain size, good dispersion and high flame retardant performence was obtained through preparing the Mg-Al hydrotalcite by high gravity reactive precipitation (HGRP), and then modifying using sodium tripolyphosphate.It was found that the Mg-Al hydrotalcite with Mg/Al molar ratio of 3 possesses high crystallinity, single crystal phase, small particle size and good thermal stability. So, it was suitable as a flame retardant material. The processing parameters were optimized for the MAH3 prepared by HGRP. The optimal process parameters of the response surface analysis (RSM) were temperature 58.17℃, reaction time for 37.57 min, the crystallization time for 4.67 h and carbon-chlorine (CO32-/Cl-) molar ratio. Under the optimal conditions, the yield rate of the MAH3 was 85.818%, which improved by about 6% compared with one in single-factor-experiment (SFE).The microstructure, thermal stability and particle size distribution of the MAH3 and modified MAH3 (SMAH3) were determined. The formation mechanism of the SMAH3 was investigated. Tripolyphosphate root (P3O105-) formed a coating on the surface of the MAH3 and SMAH3 particles, so as to improve the interfacial properties of the particles and restrain the formation of hydrogen bond among particles. The intermolecular steric hindrance of the SMAH3 was increased, while the agglomeration process was effectively controlled.The optimum operations were found by means of RSM. The lowest oil absorption value (45.03%) was obtained from 6.98 wt% sodium tripolyphosphate (STPP) at 38.10℃ for 90.01min, which decreased by 2.3% compared with one in SFE. On the other hand, the average size (580 nm) of the SMAH3 by RSM was smaller than one (670 nm) by SFE, and the particle size distribution of 255～816 nm by RSM narrower than one of 345～970 nm by SFE. So, the quality of the SMAH3 by RSM was better than by SFE.The MAH3 content has a significant influence on the composite material with MAH3 and polypropylene (MAH3-P). By adding a lot of MAH3, the MAH3-P had good flame retardant property, but the mechanical properties became worse with increase of the MAH3 content. The MAH3-P with 30%MAH3 reached the standard non-flammable plastics, and had good flame retardant property with LOI%27.2, tensile strength 20.29 MPa, flexural strength 54.68 MPa, elongation at break rate of 13.24% and impact strength 6.576 kJ·m-2. The results showed that the MAH3-P could keep the mechanical properties of polypropylene. The flame retardancy and mechanical properties of the SMAH3-P were better than those of the MAH3-P.