Flame retardant nylon is one of many modified varieties of nylon. Applications include automotive ignition system components, solar photovoltaic cell components, appliance plugs and sockets, electrical circuit breakers, and more. The flame retardant grade of the nylon before modification is about UL94 V-2. By adding a flame retardant to the nylon for modification, the flame retardant grade after modification can reach UL94 V-0.
China is a large country in the world's phosphorus resources, so red phosphorus has a great cost advantage, and its flame retardant efficiency is high, which makes it widely used. Red phosphorus forms phosphoric acid after thermal decomposition. On the one hand, phosphoric acid acts as a dehydrating agent and promotes the formation of carbon. The formation of carbon reduces the heat transfer from the flame to the condensed phase. , Reduces the heating process. It is flame retardant through the endothermic, condensed phase flame retardant mechanism.
However, in 2010, the Panasonic recall incident raised concerns about the use of red phosphorus flame retardants, because the red phosphorus can make the product's performance have some potential safety hazards. On the other hand, the color of red phosphorus also restricts it to dark nylon products such as black or red, so light-colored or transparent halogen-free flame-retardant nylons generally use melamine salts.
Melamine salts mainly include melamine cyanurate (MCA), melamine polyphosphate (MMP), etc., which have the advantages of low toxicity, low corrosion, high flame retardant efficiency, and no conflict with additives. It can be used alone PA reaches UL 94 V-0 level.
After the melamine salts are thermally decomposed, they will take away some heat and reduce the surface temperature of the PA. From the perspective of gas phase analysis, decomposition easily releases non-combustible gases such as ammonia, nitrogen, nitrogen oxides, and water vapor, which dilutes the concentration of combustible and combustion-supporting gases, preventing further combustion inside the PA. From the perspective of the condensed phase, the PA material degrades early, promotes the formation of residual carbon, and protects the interior of the matrix.
When using these flame retardants, for the purpose of reducing costs and maximizing the flame retardant effect, people will compound according to some synergistic effects, such as halogen flame retardants with gas phase flame retardant effects and solid phase flame retardant effects. The combination of phosphorus-based flame retardants can form a complete gas-solid phase flame retardant system; nitrogen-based flame retardants can promote the carbonization of phosphorus-based compounds and so on.
All in all, flame retardant nylon does not have the perfect flame retardant to choose from. Under the general trend of environmental protection, halogen-free, economical and efficient compounding is the future development direction.
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