Interactions between calcium carbonate and ammonium polyphosphate in low‐borate concentration hydrocarbon intumescent coatings

For high performance of hydrocarbon intumescent coatings, interactions between the acid source ammonium polyphosphate (APP) and inorganic fillers can be critical. In present work, low-borate concentration (ie, 1 wt% zinc borate) coatings with different ratios CaCO3 to APP were studied in an attempt map reaction mechanisms. The analysis coating was conducted using thermal insulation assessment according UL1709 fire curve (disregarding substrate load, geometrical diversity, other full-scale implications complete standard), rheological measurements, thermogravimetric analyses, attenuated total reflection-Fourier transform infrared spectrometer (ATR-FTIR), X-ray diffraction. Results show that a CaCO3/APP mass ratio 0.3 gives best longest critical time steel substrates reach both 400 550°C assessment). dependency on dynamic viscosity minimum points significant during softening state intumescence process) coating. Due enhanced anti-oxidation property, degradation zone char residual weight after exposure improved when increasing ratio. compositional development showed react form new polymeric phase, calcium catena-polyphosphate (CaP2O6). This may contribute formation compact phase benefit coatings.