Liquid polysulfide rubber (LP-3) was used as a toughening modifier to improve the toughness of polybenzoxazine obtained from bisphenol A-aniline based benzoxazine (B-a).The mixing and curing processes of B-a and LP-3 were monitored by 1H-NMR

FTIR and DSC.It was found that the ring-opening addition reaction between B-a and LP-3 happened during mixing

and the resultants showed lower curing temperature and faster curing rate than the pure B-a.The thermal and mechanical properties of the cured materials with various LP-3 incorporations were measured by TGA

DMA

impacting and flexural test.The results showed that LP-3 was an effective toughener for polybenzoxazine from B-a.Materials containing LP-3 in the crosslinked network showed much better toughness than that without LP-3.With the increase of LP-3 incorporation

impacting strength increased while modulus and glass transition temperature (Tg) decreased.When 5 wt% LP-3 was added

the impacting strength of the cured material was about 3.4 times higher than that of the polybenzoxazine from pure B-a.Simultaneously

the material at this LP-3 content retained high storage modulus (E'=3.9 GPa at 30℃) and high glass transition temperature (Tg=206℃) with improved flexural properties and thermal stability (T5%=322℃

T10%=342℃).It was concluded that LP-3 was a promising modifier for the commercial B-a resin even with small addition amount.When the amount of LP-3 was 5 wt%

the cured material owned the best overall performance.