Views: 18 Author: Site Editor Publish Time: 2022-07-17 Origin: Site
Like most polymers, EVA or EVA foam sheet is easy to burn, emits a large amount of heat, emits a large amount of smoke, and releases toxic gases, which greatly limits its application.
Nowadays, the EVA flame retardant system is mainly modified with halogen trioxide thermoplastic elastomer and applied with antimony system. When the halogen flame retardant is burned, it is easy to produce toxic and corrosive gases and a large amount of smoke, which is easy to cause secondary harm.
With the improvement of people's environmental protection and health requirements and the introduction of relevant regulations, the research and development of halogen-free environment-friendly flame retardant polymer materials has become a hot spot and trend today. When the polymer added with the intumescent flame retardant melamine polyphosphate (MPP)/pentaerythritol (PER) system burns, a uniform intumescent carbon layer will be formed on its surface.
In recent years, the flame retardant effect of hydrotalcite (LDH) has gradually been recognized by people. When LDH is burned or heated, it loses interlayer water, carbonate and hydroxyl groups, and absorbs a lot of heat in this process, which plays a flame retardant effect.
The decomposition product has a large specific surface area and strong alkalinity, which can absorb the acid gas and smoke released during thermal decomposition in time, and play the role of smoke suppression and smoke elimination. Hydrotalcite and intumescent flame retardant are combined with modified EVA thermoplastic elastomer, and the synergistic effect of the two is used to improve the flame retardant performance of EVA foam, and a green flame retardant material with high efficiency, low price, low toxicity, low smoke and no environmental pollution is prepared. .
EVA/MPP/PER/LDH composites were prepared by melt blending method, and their flame retardant properties were studied. The results show that the MPP/PER and LDH systems have a synergistic flame retardant effect, which is conducive to the formation of a continuous and dense carbon layer and can improve the residual rate of EVA thermal decomposition; when the mass ratio of EVA/MPP/PER/LDH is 60/20/10/10 , The flame retardant grade of the composite material reaches UL94V-0, and the limiting oxygen index is 30.6%.
In the thermogravimetric analysis, the initial decomposition temperature was 316 °C, and the maximum exothermic peak temperature on the DSC curve was 360 °C, which was about 50-100 °C higher than the existing IFR decomposition temperature, which could meet the processing requirements of almost all engineering plastics. At the same time, Timer is insoluble in water and most organic solvents, and does not have the disadvantage of commonly used IFR for hygroscopicity. Therefore, Trimer can be used for flame-retardant plastics and alloys in the high-tech electronic-electrical industry. This new Trimer is compounded with ammonium polyphosphate (APP) and melamine (MA) to form an intumescent flame retardant mixture flame retardant EVA. The mass ratio of flame retardant is Trimer:APP:MA=100:32: 49.
When the amount of mixed flame retardant is 30% (mass fraction), the LOI of the flame retardant system can reach about 30%, and the flame retardancy is UL94V-0 grade; Reduced by 50%~70%, 30%~40% and 50%, it has a good flame retardant effect. In addition, a uniform and dense carbon layer with a closed-cell structure was formed during combustion, with a pore size between 5 and 30 μm and a pore wall of 6 to 9 μm.
Halogen-free flame retardant EVA composites were prepared by using fumed SiO2 synergistic silane coupling agent KH550 to modify magnesium hydroxide (KH550-MH). The results show that when KH550-MH accounts for 47% of the system and SiO2 accounts for 8% of the system, the flame retardant grade of the system is V-0, and the elongation at break reaches 168%.
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