Application And Research Progress Of Hydroxide Flame Retardant In Polyethylene

2022-11-11

Polyethylene (PE) is a thermoplastic resin obtained by the polymerization of monomer ethylene. It has good cold resistance, good mechanical strength and dielectric properties. It is widely used in cables, films, pipes, packaging, containers, medical appliances and other products. But the PE oxygen index is 17.4%, which is a flammable material. PE material has a fast burning speed, a large amount of heat/smoke, and it is easy to melt and drop when burning, which poses a great threat to the safety of life and property, and limits the use and development of polyethylene. Therefore, it is imperative to carry out flame retardant modification.

Metal hydroxide flame retardants are mainly aluminum hydroxide and magnesium hydroxide. Magnesium-aluminum flame retardants have good stability, non-toxicity, and low smoke generation. During the combustion process, water vapor will be released to dilute the combustible gas, take away part of the heat, inhibit combustion, and produce a flame retardant effect. Aluminum-magnesium flame retardant can prolong the ignition time and reduce the heat release rate. The compatibility of magnesium hydroxide with PE is poor and the flame retardant efficiency is low. It needs a large amount of addition to improve the flame retardant performance, and a large amount of addition will reduce the processing of composite materials. and mechanical properties.

A research project uses sodium stearate and polyethylene glycol as modifiers to modify the surface of magnesium hydroxide, and prepare high-density polyethylene flame retardant composite materials. The research shows that when the addition amount of modified magnesium hydroxide is 30%, the tensile strength of HDPE/magnesium hydroxide composite material is 12.3MPa, magnesium hydroxide has good compatibility with HDPE, and the limiting oxygen index is increased to 24.6% , the flame retardant performance improved less.

Layered double hydroxide will release CO2 and H2O when it decomposes, dilute and block oxygen, making it have a good flame retardant effect and can replace halogen and phosphorus-containing flame retardants.

In another research project, aluminum hydroxide/Mg-Fe-LDH/HDPE flame retardant composites were prepared with aluminum hydroxide and self-made magnesium iron double hydroxide (Mg-FeLDH) as flame retardants. The study found that aluminum hydroxide and Mg-Fe-LDH can effectively inhibit the CO release and heat release during the combustion of composite materials (HDPE1, HDPE2, HDPE3), making HDPE difficult to ignite. When the total amount of flame retardants is 40% (2% of Mg-Fe-LDH, HDPE2), HDPE composites have good flame retardant properties.

Metal hydroxide flame retardants are safe, environmentally friendly and inexpensive. When used alone, the flame retardant effect is not good, and a large amount of addition is required to improve the flame retardant performance of the material, but when a large amount is added, the mechanical properties will be reduced. Therefore, it is the research direction of hydroxide flame retardant to study surface modification and use it in combination with nitrogen and phosphorus flame retardants to improve the flame retardant performance and reduce the addition amount.

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