Study On The Synthesis And Properties Of Self-curing Triphenol-based Phthalonitrile Resin

Phthalonitrile resin is a thermosetting polymer with excellent high temperature resistance,which is often used as the matrix resin of composites.However,its wide application is limited by its high curing temperature,narrow processing window,and high monomer melting point.In this paper,a novel self-curing phthalonitrile resin system was designed and synthesized from terphenol(TFPA).The obtained resin is incorporated with carborane bisphenol and epoxy resin with different proportions,and its properties were modified.The effects of dosage of carborane bisphenol and epoxy resin on the structure and properties of the mixed system were studied in detail.(1)Three TFPA-Ph systems with different phenolic hydroxyl contents(TFPA-Ph-N1,TFPA-Ph-N2,and TFPA-Ph-N3)were synthesized by the reaction of TFPA with 4-nitrophthalonitrile.Through DSC and curing rheology analysis,it was found that the TFPA-Ph system has good processing flowability,with a melting point below 120 ~oC and a wider processing window of over 90 ~oC.Property analysis shows that the higher the content of phenolic hydroxyl groups,the lower the curing temperature of the resin and the faster the curing rate;The higher the content of nitrile groups,the greater the crosslinking degree of the polymer,and the thermal oxygen stability,moisture heat resistance,and flame retardancy of the cured resin also improve.In addition,the post curing temperature also has an impact on the property of the polymer,and an increase in post curing temperature will promote the cross-linking and curing of nitrile groups,significantly improving the performance of the polymer.(2)The carborane structure was introduced into TFPA-Ph-N3 system using carborane diphenol(COH)as boron source,and the effect of its dosage on the structure and properties of phthalonitrile resin was studied.Through DSC and curing rheology analysis,it is found that COH can promote the curing of TFPA-Ph-N3,which can lead to self-curing reaction at a lower temperature,and greatly improve the processability and high temperature resistance.(3)Blending modification of phthalonitrile resin/epoxy resin(TFPA-Ph-N1/TFPA-EXOXY)was carried out,and the effect of component proportion on the structure and properties of the cured product was studied.When the ratios of TFPA-Ph-N1/TFPA-EXOXY were 3:7and 5:5,respectively,the curing temperature of the system decreased to160 o C and 164 ~oC,which was about 60 ~oC lower than the pure epoxy resin system.This confirms that the presence of phenolic hydroxyl groups in TFPA-Ph-N1 promotes the synergistic curing of nitrile and epoxy groups.The property analysis of the cured blend system showed that the compatibility of the blend system was good,and the processing performance and high-temperature resistance of the mixed resin were improved with the increase of TFPA Ph-N1 ratio.(4)The carborane structure was introduced into the binary blend system of TFPA-Ph-N1/TFPA-EXOXY with a ratio of 5:5,and the effect of its dosage on the structure and properties of phthalonitrile resin was studied.Results show that with the increase of COH content,the toughness and high-temperature resistance of the polymer increase.