Novel tetrapotassium azo diphosphonate (INAZO) as flame retardant for polyurethane adhesives

• Published in: Polymer degradation and stability Vol. 97; no. 3; pp. 375 - 382
• Main Authors: Tirri, Teija, Aubert, Melanie, Wilén, Carl-Eric, Pfaendner, Rudolf, Hoppe, Holger
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2012; Elsevier
• Subjects: Additives; Adhesives; ammonium polyphosphates; Applied sciences; Azo; biphenyl; burning; calorimeters; castor oil; Combustion; Cone calorimeters; dolomite; Exact sciences and technology; Flame retardant; Flame retardants; flammability; heat; mechanism of action; Phosphonate; Physicochemistry of polymers; Polymer industry, paints, wood; Polyurethane adhesive; Polyurethane resins; polyurethanes; smoke; Technology of polymers; Thermal degradation; Flame retardant; Phosphonate; Polyurethane adhesive; Azo; Thermal degradation; Polymer; Vegetable oil; Mechanism; Thermal properties; Additive; Smoke emission; Castor oil; Polyurethane; Ammonium Polyphosphates; Flammability; Adhesive
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2011.12.005

An inorganic azo diphosphonate (INAZO), (KO)2(O)P-NN-P(O)(OK)2·4H2O, was synthesized and tested as a novel type of flame retardant additive for castor oil and oligomeric methylene diphenyl diisocyanate (PMDI) based two component polyurethane adhesive with or without using dolomite ((CaMg(CO3)2) as filler. Flammability according to UL 94 test and performance under forced-flaming conditions (cone calorimeter) were investigated at the additive loadings of 5, 10 and 20wt %. It was shown that INAZO improves flame retardancy by significantly reducing heat release rate (HRR), maximum average rate of heat emission (MARHE) and total smoke release (TSR) values in comparison to CaMg(CO3)2 filled polyurethane adhesives. The macroscopic structure of the sample residues after cone calorimeter measurement was also analysed. The action mechanism of the developed INAZO flame retardant is suggested to be mainly in the condensed phase. UL 94 V-0 rating was achieved in the vertical burning test when 10wt % loading of INAZO was used, whereas the reference flame retardant ammonium polyphosphate (APP) required a loading of 20wt % to reach the V-0 classification.