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Additives char formers

The use of polyols such as pentaerythritol, mannitol, or sorbitol as classical char formers in intumescent formulations for thermoplastics is associated with migration and water solubility problems. Moreover, these additives are often not compatible with the polymeric matrix and the mechanical properties of the formulations are then very poor. Those problems can be solved (at least partially) by the synthesis of additives that concentrate the three intumescent FR elements in one material, as suggested by the pioneering work of Halpern.29 b-MAP (4) (melamine salt of 3,9-dihydroxy-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]-undecane-3,9-dioxide) and Melabis (5) (melamine salt of bis(l-oxo-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octan-4-ylmethanol)phosphate) were synthesized from pentaerythritol (2), melamine (3), and phosphoryl trichloride (1) (Figure 6.4). They were found to be more effective to fire retard PP than standard halogen-antimony FR. [Pg.135]

Metal chelates lower decomposition temperature (decrease thermal stability of material), increase char yield and limiting oxygen index, and improve smoke density rating. They are useful S5mergistic additives for Al(OH)3 and Mg(OH)2. Their two major functions are catalysts of dehydrochlorination and char formers. [Pg.71]

Alumina frihydrafe, by itselfor in combination with antimony trioxide, is an effective fire retardant additive (69,70). Antimony trioxide by itself has been shown to effectively reduce the smoke generated in a flexible formulation of PVC (71), as has zinc borate (72) and barium metaborate (73). Phosphate plasticizers, described earlier, are also effective as char formers (71). Smoke suppressants, as a special class of materials, are designed to reduce the... [Pg.397]

The chemistry of flame-retardant additives is highly varied and is optimised not only for specific polymer chemistries, but also to address flammability effects such as flame spread, dripping, smoke release and so on. Flame-retardant chemistry includes classes of compounds such as halogenated organics, char formers, crosslinking compounds, mineral fillers, intumescent packages, phosphorus compounds, nitrogen-based compounds and even certain metal and boron compounds. [Pg.34]

Another common FR additive for PVC formulations is zinc borate (ZB). This product is suggested as a partial replacement for antimony oxide and also functions as a smoke suppressant for vinyl composites (Fig. 9.4). ZB additionally can suppress glowing embers because it alters the surface morphology (char former) of the affected area. Use of ZB and related products, such as zinc hydroxystannate, is discussed in Section 16.5. [Pg.297]

The use of the additive molar Cpx function is restricted to polymers exempt from halogen. Halogen atoms are in-built soot formers (and consequently in-built flame retardants in the presence of oxygen) engaged in secondary reactions, thus influencing the char formation markedly. [Pg.772]

Resins are of two general types thermoplastic and thermoset plastic. The former melts every time its temperature is raised above a certain limit. This gives rise to coti-cems over its performance in elevated temperatures, because while it can be melted several times during the manufacturing process, it can also be inadvertently melted in service. Thermoset plastic covers a range of plastic resins that only melt (or flow) Mice. Typically they are manufactured in two parts (a base and an accelerator or catalyst), and when mixed and heated, they commingle and flow as a plastic. Once set in this form, they do not melt again, but on the addition of excessive heat, they will soften then char. Thus, like thermoplastics, they are also sensitive to extreme heat. [Pg.299]


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See also in sourсe #XX -- [ Pg.4 , Pg.27 ]




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Char formers

Charring

Chars

Former

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