Carbonization agents

Function Propellant and aerating agent carbonating agent direct-contact freezing agent. 

In intumescent fire retardant application, clay was combined with ammonium polyphosphate and pentaerythritol in the polypropylene matrix. The fire retarding properties depended on the composition of clay. Ammonium polyphosphate played the role of carbonization catalyst and pcnlacrylhrilol the role of carbonization agent. 

Carbon disuifide Ethane carbonation agent, carbonated beverages Carbon dioxide carbonation agent, food Carbon dioxide carbonizing agent, wooi Sodium bisuifate Sodium bisuifite carbonizing, textiies Suifuric acid... 

Refining of beet sugar Manufacture of oil and grease additives Steel carbonizing agent Glass manufacture... 

Acidic agent Carbonization agent Spumific Synergistic agent LOI volume (%) WI--94 rhr (kW/m ) ... 

The char formers commonly used in intumescent formulations for thermoplastics are polyols such as pentaerythritol, mannitol, and sorbitol. However, exudation and water solubility are problems associated with these additives. Moreover, these additives are often not compatible with the polymeric matrix, and the mechanical properties of the formulations are then very poor. We have developed intumescent polyolefin-based formulations using charring polymers [thermoplastic polyurethane (TPU) and polyamide-6 (PA6)] as carbonization agents. " These formulated blends have improved mechanical properties compared with polymers loaded with classical flame retardants, and they avoid the problems... 

As in the case of zeolite, the mechanism of action looks similar. No direct comparison can be made because MMT is a layered silicate compared to the cage structure of zeolite, and also because the carbonization agent is no longer a polyol but a char-forming polymer (PA6). Nevertheless, the main conclusion we can draw is that the action of the synergist (nanoclay or zeolite) is to stabilize in a first step the carbonaceous structure forming aluminophosphates and silicophosphates. With the nanoclay, this effect is only effective up to 310°C, whereas it is still efficient at 560°C with zeolite. To keep its protection efficient at high temperatures, the nanoclay permits the formation of protective ceramiclike material after collapse of the phosphocarbonaceous structure. Note that we did not detect any specific influence of the surfactant of the nanoclays, probably because of its low amount in the formulation. 

Curves of heat release rate (HRR) versus time for intumescent EVA-based formulations (Figure 6.11) exhibit two peaks assigned to the development of intumescence. The first corresponds to formation of a protective layer, and the second corresponds to its destruction or failure. It clearly appears that when a nanocomposite is included in the formulation (in the matrix, in the carbonization agent, or in both), the first peak heat release rate (PHRR) is reduced (from about 340 kW/m to 200 kW/m ). However, the second peak decreases only when EVAnano is used, suggesting the formation of a stronger char. Work is in progress to explain these phenomena. 

Bugajny, M. Le Bras, M. Bourbigot, S. Poutch, F. Lefebvre, J.-M. The use of thermoplastic polyurethanes as carbonization agents in intumescent blends, 1 Fire retardancy of polypropylene/thermoplastic polyurethane/ammonium polyphosphate blends. J. Fire Sci. 1999, 17(11-12), 494-513. 

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