Study On Effect Of Metal Salt On Curing Mechanism And Thermal Properties Of Polybenzoxazine

Polybenzoxazine is a sort of thermosetting resins,which has excellent mechanical properties,thermal properties,flame retardance,good dimensional stability,excellent molecular design,processing no small molecule release,near-zero volumetric shrinkage rate.However,its high curing temperature limits its application in a wide range of fields.Therefore,adding a suitable catalyst to reduce its curing temperature becomes a valuable subject.In this paper,metal salts are used to catalyze the curing reaction of polybenzoxazine.The structure of the polybenzoxazine was analyzed,the reaction mechanism was discussed,the thermal properties of the cured product were also studied.First,the effects of acetylacetone metal on curing mechanism and thermal properties of ploybenzoxazine were studied.The experimental results showed that the acetylacetone metal could reduce the cured temperature of polybenzoxazine effectively.Under the same conditions,the catalytic activity of acetylacetone metal was related to 3d orbital electronic configuration of the transition metal.In-situ IR and X-ray photoelectron spectroscopy analysis showed that the O atoms and N atoms were attacked by electrophiles and Ar-O-C?C atom side?and N-C-O?N atom side?were broken.The cured product structure included Mannich bridge and Ph-N-Ph structure.T_5%of the cured product was basically unaffected,while the thermal decomposition rate was lowered down,the char yield at 900?was increased.Secondly,the effects of triflate metal on curing mechanism and thermal properties of ploybenzoxazine were studied.The experimental results showed that triflate metal could reduce the curing temperature of polybenzoxazine more effectively.The bond between Ar-O-C?C atom side?and Ar-C-N?N atom side?was interrupted.The cured structures of polybenzoxazine consisted of aniline para position Mannich bridge,phenolic hydroxyl ortho position Mannich bridge,aniline para position methylene bridge and phenolic hydroxyl ortho position methylene bridge.The curing process would produce a small amount of C=N terminated polybenzoxazine.After adding the triflate metal,the amount of char yield at 900?was increased,the thermal degradation tended to be gentle,but T_5%of the cured product was decreased.Thirdly,ferric acetylacetonate with the nucleophile effect on the curing mechanism and thermal properties of polybenzoxazine was studied.The experimental results showed that the nucleophiles did not promote the curing process in this system.In-situ IR results showed that the conversion of the intermediate structure to phenoxyl polybenzoxazine was increased from 30%to 100%at the initial stage of the reaction,and lots of phenoxyl polybenzoxazines were formed after the opening of oxazine ring.TG results showed that the char yield of the cured product of the complex system was not as good as the cured product by adding same amount of ferric acetylacetonate.Finally,lanthanum triflate with the nucleophile effect on the curing mechanism and thermal properties of polybenzoxazine was studied.The experimental results showedthatimidazolewasbeneficialtolanthanumtriflatecatalyzed polybenzotriazine.When complex system catalyzed polybenzoxazine,the curing mechanism slightly changed,imidazole could be combined with the structure of benzoxazine intermediates.T_5%of the cured product was increased with the addition of imidazole.