Hydrophobic modification of pentaerythritol and its application in fire-retardant coatings for steel structures

Pentaerythritol (PER) is generally used as carbon source in intumescent fire- retardant coating. In order to enhance water resistance of the coating, PER reacted with C9 maleic anhydride copolymer microsphere (C9-MAH) by esterification. The composition of the product PER-C9-MAH was analyzed by FTIR; TGA results show the thermostability of PER-C9-MAH is better than PER; and SEM observation clearly showed the obvious enlargement in particle size from PER to PER-C9-MAH. The contact angle of PER is 26.5° and it raised to 87.2° for PER-C9-MAH. The fire resistance changes of the coating before and after water/salt water soaking are compared. After soaking in distilled water and 5 g/L salt water for 48 h respectively, phenomena such as blistering and falling off will be found in the coating containing PER accompanied with 1.9 ± 0.01% (in water) and 2.4 ± 0.01% (in salt water) weight losses; however the coating containing PER-C9-MAH looked smooth with little defects, and the weight losses are just 0.3 ± 0.01% (in water) and 0.3 ± 0.01% (in salt water) respectively. After burning 30 min, the back temperature of coating containing PER raises 76.2 °C (soaked in water) and 157.0 °C (soaked in salt water) respectively; However, it is just 19.7 °C and 33.7 °C rise for coating containing PER-C9-MAH. TGA, SEM and Raman spectroscopy results document the char of the coating containing PER-C9-MAH shows higher quantity, density and degree of graphitization, so it exhibits enhanced strength.