Study On Dopo Derivatives Flame Retardant Unsaturated Polyester Resins

Unsaturated Polyester Resin(UPR) is one of the most important thermosetting resins.General UPR is highly flammable, therefore we need the flame retardant unsaturated polyester resins in many fields. According to the trend of developing halogen-free flame retardant and the damage to the UPR from additive flame retardant, it is very necessary to develop reactive flame retardant which have good compatibility with UPR, high thermal stability and efficient flame retardncy.9,10-dihydro-9-oxa-10-phosphahenanthrene-10oxide(DOPO) and its derivatives have high thermal stability,were used as reactive flame retardants for many polymers. In this thesis,two DOPO derivatives were prepared and participated in the general UPR polycondensation reaction to get UPR good in flame retardancy. This thesis systematically studied the relationship between the amount of two derivatives and properties of UPR, such as retardancy, thermal stability and curing reaction; deeply analysed that how the structures of derivatives affected retardancy, thermal stability and curing reaction; made use of Scanning Electron Microscopy(SEM), Fourier Transform Infrared Spectroscopy(FTIR) and Thermal Gravimetric Analysis(TGA) to explore flame retardant mechnism.Two DOPO derivatives were synthesised and the derivatives involved in the polycondensation reaction to prepare reactive flame retardant UPR. DOPO reacted with maleic acid and itaconic acid to get DOPO derivatives DOPOMA and DDP. They respectively reacted with phthalic anhydride, maleic anhydride, propylene glycol to prepare DOPOMA flame retardant UPR (P1-UPR series) and DDP flame retardant UPR (P2-UPR series). Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) proved that DOPOMA and DDP involved in the polycondensation.The flame retardant amount increased, the limited oxygen index(LOI) of P1-UPR series and the P2-UPR series increased, and flame retardancy was improved,but DDP had better retardancy than DOPOMA did. When the amount of DOPOMA was 24%, it could achieve UL-94 V-1 level and LOI was 25.4%. When the amount of DDP was 18% ,it could achieve UL-94 V-0 level and LOI was 29.0%. Cone calorimeter tests also showed the good flame retardancy of P2-UPR series.Using TGA to study that how amount and structure of the flame retardant affected the thermal stability of P1-UPR series and P2-UPR series. It showed that the thermal stability of P2-UPR was the best,and P1-UPR was close to UPR0; UPR0 residue was only 3.4%, P1-UPR3 increased to 6.1%, while P2-UPR3 was as high as 10.3%, and the order was consistent with flame retardancy.FTIR and SEM test results for residue carbon layer showed that the P concentration in surface was greatly increased and it had a compact structure, indicating that the condensed phase flame retardant mechanism was the main.It showed that, using benzoyl peroxide and N, N-dimethyl aniline accelerator, flame retardants had no effect on the cure of UPR. However, using methyl ethyl ketone peroxide initiator and Co accelerator, DOPOMA and DDP would delay the cure of UPR.The curing kinetic parameters and curing parameters were obtained from the above DSC curves. The apparent activation energy(Ea) of P1-UPR3 and P2-UPR3 were 73.67, 57.41 kJ/mol, both higher than the UPR0 with Ea of 48.38 kJ/mol. Curing parameters for UPR0, P1-UPR3 and P2-UPR3: gel temperature was 52,84 and 75℃;cure temperature was 60,103 and 92℃; post-cure temperature was 93,121 and 106℃.