Thermally Catalyzed Curing Of Bisphenol A Type Benzoxazine/iodonium Salt

Polybenzoxazine resin is a kind of high performance thermoset resins developed in recent years, which polymerized from benzoxazine monomer. Benzoxazine is a molecule where an oxazine ring (a hetero-cyclic six-membered ring with oxygen and nitrogen atom) is attached to a benzene ring. Polybenzoxazines has a number of unique properties such as easy to synthetize, cheap raw material, near-zero volume changes, high glass transition temperature, and low water absorption, good thermal and mechanical properties. Benzoxazine has flexible molecular design and good compatibility with general resins, like phenolic resins, epoxy resins and bismaleimide resins. Therefore, polybenzoxazine has been applied in military, aeronautics and astronautics, auto and electronics fields. But the curing reaction normally takes place at a temperature above 200?, limiting the applications of benzoxazine. This paper studies the catalytic effect of diaryliodonium salts (Arlx) on thermal curing of bisphenol A-type benzoxazine, meanwhile, the cure degree and the influence of diaryliodonium salts on thermal and mechanical properties is also investigated. The cure kinetics is also studied based on DSC technology with Kissinger and Ozawa method.In this study we introduce diaryliodonium tetrafluoroborate (DT), diphenyliodonium hexafluorophosphate (PF) and diphenyliodonium hexafluoroarsenate (AS) to catalyze bisphenol A-type benzoxazine (BA). The cure reactions of BA with and without diaryliodonium salts as catalyst are monitored by using differential scanning calorimetric (DSC) and in-situ fourier transform infrared spectroscopy (in-situ FTIR). Both initial and peak curing temperature (T,-and Tp) of BA decrease significantly in presence of diarylionium salts. The curing degree and polymerization rate of BA monomers increased significantly with catalyst. The curing degree of BA and BA/ArIx curing at 180?,200? and 220? were investigated respectively. Non-isothermal DSC was utilized to study the curing kinetics of BA and BA/ArIx systems. Similar to neat BA, BA systems with catalyst also followed an autocatalytic kinetic model.Bisphenol A-type benzoxazine and benzoxazine with diarylionium salts were cured at 180? for 2h followed by 200? for 2h to form crosslink structure named PBA and PBA/ArIx. Thermo gravimetric analyzer (TGA) and dynamic thermomechanical analysis (DMA) were induced to study the thermal and dynamic mechanical properties of PBA and PBA/Arlx system. It is shown that, small amount of ArIx could improve the char yield of polybenzoxazine, meanwhile, the glass transition temperature (Tg) and storage modulus (25?) of PBA is 200? and 4715 MPa, while Tg and storage modulus (25?) for PBA/DT-1 (BA:DT=99:1 by wt), PBA/PF-1(BA:PF=99:1 by wt) and PBA/AS-1(BA:AS=99:1 by wt) system are 207? and 6974MPa,213? and 7069MPa,205? and 6611 MPa, this indicates that the present of ArIx could improve the thermal mechanical property of PBA.