| Abstract: | The object of this study was to identify, for future large-scale testing, and adequate fire-protective coating for the substrate, polyvinyl chloride (PVC) nitrile rubber (MIL-P-15280 Rev H). Fifteen fire protective coatings which included ten intumescent, two ablatives, two fire retardants and one photon diffusive coatings were evaluated using bench-scale thermal insults. To discern the possible mechanism(s) whereby the coatings offer fire protection, the effect of radiant heat versus the flame source employed was investigated and thermogravimetric analysis (TGA) of the neat coatings was performed. In selected cases, the effect of coating thickness and repeatability of the results were evaluated. The differences in coating effectiveness, and the varied repeatability in three of the four cases examined, focus on the inherent complexity of intumescence, as well as on the importance of scaled-up testing of coatings that appeared promising. Thermogravimetric analyses of the coatings indicate that two selected TGA measurements/parameters, when used in conjunction, appear useful in characterizing mechanistic differences between the less effective and more effective coatings. Based on the rigorous criterion adopted, one candidate (a water-based intumescent coating at 100 mil (2.54 mm) thickness) appears promising for the substrate, PVC nitrile rubber. Its effectiveness is attributable to it exhibiting good insulative and re-radiative properties and an apparent low susceptibility to crack formation. |
