||Intumescent fire-retardant paints were mainly including ammonium polyphosphate(APP), melamine and pentaerythritol These three chemicals |
are the main structure of the expansion system. Ammonium polyphosphate is an inorganic polymer containing phosphorus and nitrogen. This chemical APP has high content of P-N of flame retardant, good thermal stability, non-toxic and smoke-inhibiting. It is often used as a halogen-free flame retardant of nitrogen-phosphorus-based expanded in various fields. In particular, the coatings of flame retardants are gradually becoming a research hotspot. The chemical APP of I-type structure has linear chains of different lengths, low decomposition temperature and high water solubility. The chemical of APP Type II structure is water-insoluble substance. This APP has crosslinked structure existing in the crystal and the degree of polymerization can reach more than 1000. Thus APP of type II is more inclined to be used in the application.
In this study, three different types of APP were selected: APP I, APP II, and APP II Coating MF. These three APPs were added to the fire retardant paint. Physical properties tests , wooden board trial burn and gas burner tests were conducted.
The results of all tests show that the expansion layer was not thick enough and there was void in the inner layer of the expansion when tests of wooden board trial burning on APP I type.This finding would cause a poor flame-retardant effect. While the APP II type and APP II Coating MF was found the thickness and density of the intumescent layer increased after board burning test.After the gas burner test, the fire-resistance of fire-resistance of APP type I was only reach 25 minutes, the APP II type was reached 71 minutes, and the APP II Coating MF was reached 77 minutes.Finally,the APP II coating MF has good aging of fire retardant .