Synthesis And Flame Retardancy Of Alkyd Resin Chemically Modified By Two DOPO Derivatives

Alkyd resin is usually synthesized through esterification polycondensation reaction. It has advantages of simple manufacturing process and excellent comprehensive performance of film, leading to its wide application. But its flammability is a fire hazard which should be taken into account for its production, transportation and storage processes. To eliminate or diminish the fire hazard, it is necessary to improve its flame retardancy through adding flame retardants or combining flame retarding groups.9,10-dihydro-9-oxa-10-phosphahenanthrene-10-oxide (DOPO) and its derivatives are often used as additive or reactive flame retardants for many polymers. In this study, the DOPO derivative 2-[10-(9,10-dihydro-9-oxa-10-phosphaphenantrene-10-oxide-10-yl)]-maleic acid (DOPO-MA) was synthesized from DOPO and maleic acid by addition reaction. Further it was reacted with soybean oil fatty acid, pentaerythritol, phthalic anhydride to prepare one kind of flame retarded alkyd resin (MAALK). Similarly, another DOPO derivative 6-((Bis(2-hydroxyethyl)amino)methyl)-6H-dibe-nzo[c,e][1,2]oxaphosphinine 6-oxide (DHDOPO) was synthesized with DOPO, diethanolamine and paraformaldehyde as raw materials and was used to prepare another kind of flame retarded alkyd resin (DHALK). Fourier transforms infrared spectroscopy (FTIR) and nuclear magnetic resonance hydrogen spectrum(1H-NMR) proved that two kinds of flame retardants involved in the polycondensation reaction of alkyd resin. The cone calorimeter test results showed that the flame retardancy of MAALK and DHALK was better than that of the common alkyd resin without flame retardants (ALK) and increased with the content of phosphorus. Under 50 kW/m2 external heat flux, the ignition time, the peak heat release rate (PHRR), the total heat release (THR) and the fire residue of ALK were respectively 7s,1145 kW/m2,82 MJ/m2 and 0.2%. For MAALK and DHALK, when the mass fraction of phosphorus reached 2.5%, the ignition time respectively extended to 16s and 14s, PHRR respectively decreased to 722 kW/m2 and 652 kW/m2, THR respectively decreased to 45 MJ/m2 and 34 MJ/m2, the residue respectively increasing to 12.9% and 16.8%. In addition, thermogravimetric analysis (TGA) revealed that the thermal stability of MAALK and DHALK was improved significantly, and the residue increased from 1.43%(ALK) to 3.75% and 8.92% respectively. The test results of film performance showed that the impact resistance of DHALK decreased with increasing the mass fraction of phosphorus. Most performances met the national standard requirements for alkyd varnish except the drying time of DHALK and MAALK. Further, the water resistance of MAALK containing relatively large amount of phosphorus did not meet the national standard.In order to reduce the drying time, on the one hand, the soybean fatty acid was partly substituted by the linoleic acid to obtain MADY and DHDY respectively corresponding to MAALK and DHALK. The cone calorimeter test results showed that as the content of DOPO derivative increased both PHRR and THR decreased and the fire residue gradually increased. The flame retardancy of MADY and DHDY was respectively worse than that of MAALK and DHALK, although the drying time and water resistance of MADY and DHDY met the national standard. On the other hand, with MAALK and amno resin as raw materials, amino-alkyd baking paint (FRA) was prepared. But it was found that the impact resistance of FRA was worse than the national standard of amino-alkyd resin coating, and the flame retardancy of FRA was worse than that of MAALK.