Polyurethane foams based local montmorillonite (magnite) as intumescent materials

Abstract

In the present framework, we aimed to elaborate intumescent composites polyurethane/ organically treated montmorillonite (PU/ OMMT) foams by the use of local “Bentonite” called “Maghnite”. These composites were elaborated via an in situ polymerization. The first stage relates to the organic treatment of the montmorillonite (MMT) using an alkylammonium (hexadecylamine C₁₆H₃₅N) in order to increase the interfoliate distance, resulting in an organically compatible modified montmorillonite (OMMT). The second one is reserved to the optimization of the polyurethane (PU) formulation. Composite’s foams (PU/ OMMT) are formulated via the free expansion process. Moreover, the physicochemical characterization of the developed foams was carried out. Characterization of the obtained foams have been done by various methods such as: FTIR, DSC, TGA, XRD, SEM, Charpy test, and normalized flammability test (UL 94 HB). FTIR analysis confirms the PU formation and the incorporation of the organically treated montmorillonite (OMMT) into the polyurethane (PU) via the in-situ polymerization. Add to that, it is assigned by the XRD analysis that the interfoliate distance has been increased from 11.63°A to 27.96°A using the hexadecylamine and the PU/ OMMT composite foams present a mixture of intercalated and exfoliated structure. The SEM images prove that the addition of 5 wt % of OMMT has resulted in similar cell size compared to the pristine PU formulation (about 100 µm). DSC and TGA analysis proved the good thermal stability of PU foams and confirmed that the PU/ OMMT composite foam is the most stable one. Regarding the fire behavior, the obtained foams are in accordance with the normalized flammability test. The strength and tenacity test revealed improved mechanical properties in comparison to those not treated.