Chapter 11
Downloaded by PENNSYLVANIA STATE UNIV on September 17, 2012 | http://pubs.acs.org Publication Date: September 15, 2001 | doi: 10.1021/bk-2001-0797.ch011
Use of Carbonizing Polymers as Additives in Intumescent Polymer Blends M . Le Bras and S. Bourbigot Laboratoire de Génie des Procédés d'Interactions Fluides Réactifs-Matériaux, E.N.S.C.L., BP 108, F-59652 Villeneuve d'Ascq Cédex, France
Intumescence is one way to obtain effective halogen-free fire retarded polymeric systems. The first generation of intumescent systems consisted of mixtures of polyols as carbon sources together with sources of acid, typically ammonium polyphosphate, A P P . The development of the corresponding materials is limited by low compatibility between the host matrix and additives, eventual reaction between the additives during processing or polyols hydrolysis and subsequent exudation. A solution consists in the substitution of the polyols by polymers which undergo a natural carbonization upon heating: thermoplastic polyurethanes, polyamide-6 or clay-polyamide-6 nanocomposites. This study shows that mixtures of these polymers with ammonium polyphosphate are effective fire retardant additives in EPR, PP, PS and E V A . Finally, it is shown that F R performances of polyamide-6 based material are preserved after an artificial aging.
Fire protection of flammable materials via an intumescence process has been known for several years: intumescent materials on heating form foamed cellular charred layers on the surface. These layers act as a physical barrier which slows down heat and mass transfer between the gas and condensed phase.
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© 2001 American Chemical Society
In Fire and Polymers; Nelson, G., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2001.
Downloaded by PENNSYLVANIA STATE UNIV on September 17, 2012 | http://pubs.acs.org Publication Date: September 15, 2001 | doi: 10.1021/bk-2001-0797.ch011
137 Generally , intumescent formulations contain three active ingredients: an acid source (such as ammonium polyphosphate (APP) used in this work), a carbon source and a blowing agent. The first generation of carbon sources used in intumescent formulations for thermoplastics consisted of polyols such as pentaerythritol, mannitol or sorbitol (1, 2). Problems with this kind of additives consist in migration/blooming of the additives, water solubility of the additives and reaction with the acid source during processing of the formulations (2-4). Moreover, there is not a good compatibility between the additives and the polymeric matrix and the mechanical properties of the polymer are comparatively poor. Recently, we have developed fire retardant (FR) intumescent formulations using charring thermoplastic polymers (thermoplastic polyurethanes (TPU) (5), polyamide-6 (PA-6) (6) and hybrid clay-PA-6 nanocomposites (PA6nano) (7,
