Glass fiber reinforced polyester, also known as polyester FRP, one of its main components is composed of an unsaturated polyester resin and glass fiber. Because of its easy processing, light weight, high strength, corrosion resistance, good electrical and thermal function, low cost and other characteristics, it is widely used in industry, construction, transportation, mining and other fields. However, FRP made of polyester resin is combustible, 20% is unsaturated resin oxygen index of incineration (LOI), and thus the practical use of the need to enhance the flame retardant function of FRP.
The application of magnesium hydroxide in glass fiber
In the past, halogen-containing organic flame retardant is the most used method, but in the burning will release a lot of black smoke and toxic gases, has been gradually restrained to use. Over the years, for the consideration of fire prevention and safety of life and property, the need for polyester fiberglass with halogen-free, smoke suppression, flame retardant and other functions is becoming more and more urgent. Therefore, a new inorganic flame retardant – magnesium hydroxide has been more and more widely used.
In the past in the flame retardant FRP, aluminum hydroxide is the most used inorganic flame retardant, has increased, non-toxic, flame retardant, smoke suppression and many other advantages, but the defect of ATH flame retardant is a low heat-resistant temperature, heat temperature territory 205 ℃ is stable, once beyond 220 ℃ is the occurrence of differentiation. Therefore, in the use of this type of polyester FRP to pay attention to the temperature boundary of 205 ℃, the scope of application is bound by a certain limit.
Compared with aluminum hydroxide, magnesium hydroxide flame retardant and smoke elimination mechanism and aluminum hydroxide is very similar, but magnesium hydroxide has a variety of aluminum hydroxide does not have the outstanding advantages.
First of all, magnesium hydroxide differentiation temperature is high, heated to 340 ℃ before the beginning of differentiation into water and magnesium oxide, not only good flame retardant effect, but also to meet the needs of the market for higher temperature resistance of flame retardant glass fiber reinforced plastic.
Secondly, magnesium hydroxide differentiation generated by the active magnesium oxide is easy to absorb free radicals and carbon, which can delay the material ignition time. Its catalytic oxidation function can cut the smoke generation and escape rate.
In addition, the smoke suppression ability of magnesium hydroxide is double that of aluminum hydroxide, which can better prevent the pollution of the environment when burning. And magnesium hydroxide processing process is short, the production cost is low, the market price is only half of aluminum hydroxide, but the flame retardant effect is equivalent to increase the amount of aluminum hydroxide.
In addition, the coupling agent modified magnesium hydroxide treatment, can increase its increase within the polyester FRP, help to improve the oxygen index value, further reduce costs. And it is also feasible to use magnesium hydroxide alone as the flame retardant of polyester FRP.