Char and intumescence mechanism
During combustion a carbonaceous crust forms, isolating the polymer from oxygen and blocking the flame. This is the principle behind DG HF 2000.
The mechanism
During combustion, halogen free flame retardants work through a mechanism known as char formation and/or intumescence. They cause a carbonaceous crust to form which is entirely inert to combustion, and which hinders or limits contact between oxygen and the polymer.
Without oxygen reaching the material, combustion is not sustained and the flame goes out. The crust acts as a physical barrier protecting the polymer beneath it.
The swelling
Intumescence produces a swelling of the product that limits flame propagation. Retardants of this kind achieve very good performance even at moderate loadings, which allows the mechanical properties of the polymer to be preserved. The absence of halogens further reduces their hazard compared with halogenated retardants.
De Grandi’s DG HF 2000 is an intumescent flame retardant based on phosphorus and nitrogen: it uses precisely this mechanism, producing a homogeneous char with a closed-cell structure.
The test
The performance of intumescent additives is measured with the UL 94 Vertical Burn Test: class V-0 — the highest — requires the flame to self-extinguish with no dripping of the specimen, which could otherwise spread the fire. Class V-2 permits flaming drips.
DG HF 2000 achieves the V-0 classification, and class B s1 d0 under UNI EN 13501-1. It is the direct result of the intumescent mechanism.
All DG HF 2000 dataFAQ
It is a retardant that, during combustion, causes a carbonaceous crust to form together with a swelling of the material. The crust (char) is inert to combustion and hinders contact between oxygen and the polymer, while the swelling limits flame propagation. Without oxygen to sustain combustion, the flame goes out.
The char mechanism consists in the formation of a carbonaceous crust on the surface of the burning material. This crust is entirely inert to combustion and acts as a physical barrier: it limits or prevents contact between oxygen and the polymer beneath, interrupting the supply that feeds the flame.
They are two aspects of the same protective process. Char is the inert carbonaceous crust that forms and isolates the polymer from oxygen. Intumescence is the swelling of the product that accompanies char formation and physically limits flame propagation. DG HF 2000 uses both, producing a homogeneous closed-cell char.
Less than inorganic retardants do. Intumescent retardants achieve very good performance even at moderate loadings, which allows the mechanical properties of the polymer to be preserved. This is an advantage over inorganic retardants such as the hydroxides, which require very high loadings and compromise the properties of the material.
DG HF 2000, the intumescent produced by De Grandi, achieves a V-0 classification in the UL 94 Vertical Burn Test: the highest available, with the flame self-extinguishing and no dripping. It also reaches class B s1 d0 under UNI EN 13501-1 on reaction to fire.
De Grandi produces DG HF 2000, a non-halogenated intumescent retardant for polyolefins, at its plant in Tromello, in the province of Pavia, Italy. To evaluate its use on your compound you can contact the company on +39 0382 868402 or at info@degrandisrl.it.
