Types of Halogen-Free Flame Retardants:
Intumescent Flame Retardants:
Intumescent flame retardants are char forming additives that form a protective barrier of carbon foam film in the condensed phase. The protective layer is formed on the polymer's surface in response to heat which protects the product from being burnt.
This carbon char acts as a barrier or insulating layer that interrupts the combustion process from further occurring. Char forming flame retardants offer robust protection by preventing fuel molecules from reaching the flame front and thereby protect the polymer from further depolymerization.
Intumescent coatings also don't need synergists to improve the effectiveness and don't degrade the mechanical properties of the polymer. They are often used for applications that require high levels of flame protection, such as building and construction, aerospace, military, wire & cable, automotive, and transportation applications.
Organophosphorus Flame Retardants:
These types of flame retardants react chemically with free radicals in the gas or the condensed phase during combustion. They act as radical scavengers that are activated by the release of temperature. Unlike halogen compounds, they typically don't need synergists to be effective but can be combined with other halogens to enhance the protection and loading rate.
Ammonium polyphosphate is one of the most popular non-halogenated phosphorus-based flame retardants. Phosphate esters are supplied in liquid form and highly effective in urethane foams and engineered resin systems. Although phosphorus compounds are very effective and can be used in various applications, they tend to generate smoke and carbon monoxide gas.
Endothermic Flame Retardants:
Endothermic flame retardants are mineral-based additives such as aluminum trihydrate (ATH) and magnesium hydroxide (Mg(OH)2). They act by the release of water and carbon dioxides that dilutes the fuel available for combustion. Endothermic decomposition cools down the condensation phase, slows down degradation, and absorbs the fuel combustion heat.
Although mineral fillers are lower in cost and are considered to be greener chemistries, they require higher loading rates to reach the desired level of protection. The higher level of mineral fillers can also affect the polymers' mechanical properties.
The Benefits of Using Non-Halogenated Flame Retardants:
- Non Halogen flame retardants are non-toxic and do not release harmful gases during combustion.
- Unlike halogen compounds, non-halogenated compounds are not persistent and do not cause bioaccumulation.
- Non-halogenated flame retardants can function independently and do not require a synergist to provide the necessary performance.
- Halogen-free flame retardants are regarded as greener additives and have no environmental scrutiny or regulatory concerns.
PhosGard® APP is a fine particle flame retardant that is based on modified Ammonium Polyphosphate that is excellent for use in water-based coatings, polyurethanes, thermosets, and polyolefins.
PhosGard® NH4 is a halogen-free phosphate-based flame retardant with low scorch and low volatility. It is excellent for use in flexible urethane foams, engineered resins, and PVC systems.
CharFlam 200-M is a micronized melamine-based intumescent flame retardant that provides superior protection to paints, coatings, and textiles.
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