Synthesis of a novel phosphonate flame retardant and its application in epoxy resins

A novel phosphonate flame retardant additive bis(2,6-dimethyphenyl) phenylphosphonate (BDMPP) was synthesised from phenylphosphonic dichloride and 2,6-dimethyl phenol

Chinese researchers blended BDMPP into epoxy resins to prepare flame retardant thermosets. Source: Tobias Bräuning/ -

Its chemical structure was characterised by Fourier transform infrared (FTIR) spectroscopy, 1H and 31P nuclear magnetic resonance. The prepared BDMPP and curing agent m-phenylenediamine were blended into epoxy resins (EP) to prepare flame retardant EP thermosets. The effect of BDMPP on fire retardancy and thermal degradation behaviour of EP/BDMPP thermosets was investigated by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimeter and thermalgravimetric analysis (TGA). The morphologies of char residues of the EP thermosets were investigated by scanning electron microscopy (SEM) and the water resistant properties of thermosets were evaluated by putting the samples into distilled water at 70°C for 168 h.

Thermosets show excellent flame retardancy

The results demonstrated that the cured EP/14 wt % BDMPP composites with the phosphorus content of 1.11 wt % successfully passed UL-94 V-0 flammability rating and the LOI value was as high as 33.8%. The TGA results indicated that the introduction of BDMPP promoted EP matrix decomposed ahead of time compared with that of pure EP and led to a higher char yield at high temperature. The incorporation of BDMPP enhanced the mechanical properties and reduced the moisture absorption of EP thermosets. The morphological structures of char residue revealed that BDMPP benefited to the formation of a more compact and homogeneous char layer on the materials surface during burning, which prevented the heat transmission and diffusion, limit the production of combustible gases and then lead to the reduction of the heat release rate. After water resistance tests, EP/BDMPP thermosets still remained excellent flame retardancy.The study is published in: Journal of Applied Polymer Science, Volume 132, Issue 45, December 5, 2015.

Interested in more research and development in flame retardant coatings?

Check out the programm of the EC CONFERENCE “Fire retardant coatings” here The following companies and institutions will report on recent developments: Budenheim, Clariant, EMPA, Albemarle, Lehmann&Voss, Fraunhofer, Wacker, Université Lille.

These two paint manufacturers will also give insights in new systems: Sika and AkzoNobel

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