Preparation And Fire Retardant Mechanism Study For The Intumescent Unsaturated Polyester Resin Coating

To meet the growing demand for environmental protection, intumescent flameretardant (IFR), without halogen elements, is developed rapidly. In numerousintumescent flame retardants, phosphorus compounds, especially phosphate ester andaromatic phosphate ester, are suitable to replace halogen flame retardant agent.Unsaturated polyester resin (UPR) has been extensively applied as the corrosionresistance coating of steel components, chemical equipment, and automotive parts,due to many excellent properties, including electrical insulation, low volatility,adequate mechanical strength, excellent fullness, good corrosion resistance and hightransparency. For UPR modified with dicyclopentadiene (DCPD), char-layer wasformed rapidly after burning, which could protect the inner material. Therefore, theflame resistance of unsaturated polyester resin coating was further improved. In thispaper, intumescent unsaturated polyester resin flame-retardant coating was preparedby the introduction of composite flame retardant and the flame-retardant mechanismwas simultaneously investigated.The concrete research content as follows:1. The intumescent fire-retardant coating was prepared with unsaturatedpolymer resin modified with dicyclopentadiene (DCPD) as binder and ammoniumpolyphosphate (APP) and triphenyl phosphate (TPP) as compound fire retardant. Thedosage of components was optimized by measuring the fire-resistant time, and theoptimum ratio of the UPR/APP/TPP was40:29:29.2. When the content of composite flame retardant was58wt.%, the limitingoxygen index (LOI) value increased from20.9to27.2, and a V-0rating in UL-94testwas obtained. The flame-resistant time reached26~34minutes. The results of thermo-gravimetric analysis (TGA) and differential scanning calorimeter (DSC) showed thatthe char yield was improved by the introduction of APP and TPP. The major product of the decomposition of thephosphorous flame retardant was phosphoric acids whicheffectively promoted the cross-linking reaction during the burning process.3. The flame-retardant mechanism of DCPD-modified unsaturated polyesterresin intumescent flame-retardant coating was deeply investigated with advancedapparatus and analysis method such as TGA, DSC, SEM and FTIR. It wasdemonstrated that when heating, phosphorus compounds degraded to formphosphorus acid derivatives which esterify and dehydrate the pyrolyzing polymer.Simultaneously, nonflammable gas released by aromatic phosphates can reduce theconcentration of oxygen and blow the charring product to form a compact and firmcarbonaceous layer, which acts as a physical barrier to shield the oxygen flow andthermal radiation. It was indicated that the excellent flame resistance was achieved byadding APP and TPP to UPR.