Studies On Ternary Composites Of Polymer/crosslined Rubber Particle/nano-magnesium Hydroxide And The Relationships Of Their Microstructure And Properties

A new approach of fabricating polymer/nano-magnesium hydroxide (NMH) halogen-free flame retarded composites was developed in this dissertation in order to study the dispersability of NMH and the relationship between microstructure and properties of the composites. Several kinds of polymer/NMH halogen-free flame retarded composites with different microstructures like full-separation structure and encapsulation structure were prepared by this method. The relationships between microstructure and properties of related ternary composites were investigated in detail.In this experiment, a compound flame retardant (CFR) of ultra-fine full-vulcanized rubber particle (UFRP)/NMH was firstly prepared based on crosslinked rubber latex and NMH slurry. The ternary composites of ethylene vinyl acetate copolymer (EVA)/CFR and polyamide 6 (PA6)/CFR were prepared by melt-blending CFR with EVA or PA6 using an inner mixer or a twin screw extruder.Observation by transmission electron microscope (TEM) on both EVA/CFR and PA6/CFR ternary composites showed that the new approach is in favor of NMH dispersion. Cone calorimeter test (CCT) revealed that EVA/CFR and PA6/CFR ternary composites have better flame retardancy than EVA/UFRP/NMH and PA6/UFRP/NMH which were prepared by conventional melt-blending process. EVA/CFR and PA6/CFR ternary composites presented longer ignition time and lower heat release rate in initial period after ignition than related conventional-obtained temary composites. It was found that that better NMH dispersion resulted in higher thermal stability, which is also the main reason for the improved flame retardancy.Synergistic effect on flame retardancy was found between acrylonitrile butadiene (NB)-UFRP and NMH in EVA/NB-CFR temary composite. The CCT data revealed that the addition of NB-UFRP into EVA/NMH system not only reduced the heat release rate, but also prolonged the ignition time of the composite. Thermodegradation analysis (TGA) and Fourier Transform Infrared spectroscopy (FT-IR) result indicated that there exists certain interaction between EVA and NB-UFRP in the composite of EVA/NB-CFR and EVA/NB-UFRP. As a result, the inclusion of NB-UFRP into EVA/NMH system obtained us better thermal stability and therefore improved flame retardancy. In addition, NB-UFRP also helps to get good NMH dispersion which is another reason for the synergism of flame retardancy. In this article, we also studied by comparison the ternary composites of EVA/NB-CFR and EVA/carboxyl acrylonitrile butadiene (CNB)-CFR. It was found that the inclusion of different UFRPs resulted in different micro-morphology. EVA/NB-CFRs have the tendency to form full separation structure, while EVA/CNB-CFRs to form encapsulation structure.Investigations on the relationship between the microstructure and flammability indicated that full separation structure of EVA/NB-CFR benefits the material on the resistance to ignition, while the encapsulation structure of EVA/CNB-CFR is in favor of lowering the material's heat release rate during its combustion.Studies on EVA/Silicone (Si)-CFR ternary composites revealed that the incorporation of Si-UFRP can not only improve the mechanical properties, but also shows a synergism between Si-UFRP and NMH on the flame retardancy of EVA composites. EVA ternary composite modified by Si-CFR, which is a combination of Si-UFRP and NMH, presented better flame retardancy than either of EVA/Si-UFRP or EVA/NMH binary composites. Reasons for this synergism were also investigated in the dissertation.