Study On Synthesis And Curing Reaction Of Epoxy Terminated Poly(Phthalazinone Ether Sulphone Ketone)

Poly(phthalazinone ether sulphone ketone)(PPESK)possesses heat resistance(T_g, 263～305℃),radiation resistance,excellent mechanical properties and reasonable solubility due to introduce the twisted non-coplanar phthalazinone moiety,sulphone,ketone and ether into the main chain of polymer,and PPESK has widely used in high-temperature coating, high-temperature membrane and composites fields.To broaden the application of PPESK in heat resistant adhesive field,the best modification is that reactive groups can be pendant groups or end capped groups of PPESK.A kind of thermoset cross-linkable PPESK will be obtained and can be used in high-temperature adhesive field.In this paper,epoxy-terminated PPESK(E-PPESK)was synthesized using 4-(4-hydroxyphenyl)-2,3-phthalazin-l-one(DHPZ),4,4'-dichlorobenzylsulfone(DCS),4,4'-difluo-robenzophenone(DFK),2-(chloromethyl)oxirane(ECH)as raw materials by nucleophilic substitution polymerization in solution with three methods.The molecular weight and distribution of the product E-PPESK was measured by GPC.The structure of E-PPESK was ambiguously confirmed by FT-IR,¹H-NMR and ¹³C-NMR.Analyzing the results of ¹H-NMR spectra of E-PPESK obtained from different three synthetic methods,the third is the best method because of the strongest resonance peaks of epoxy end groups and the best stability of E-PPESK.The influences of reaction temperature and reaction time on epoxy end group content of E-PPESK were studied.Optimum reaction condition was that the PPESK oligomer was reacted with ECH at 100℃for 10h by tracking the content of the end capped epoxy of the product by FT-IR and ¹H-NMR.Its number-average molecular weight calculated by ¹H-NMR spectra of E-PPESK was similar with that detected by GPC.Curing performances to E-PPESK of seven curing agents were studied,of which five cure agents were selected to cure E-PPESK.The peak temperatures when heating-up rates is zero were calculated according to their DSC curves,and then the optimum curing technology parameters were obtained.Based on the Kissinger formula,Ozawa formula and Crane formula,the apparent activation energy(E_a)and reaction series of curing reactions were calculated.The results of studies on dosage of five curing agents show that the optimum dosages were close to the calculated values.The largest gel content of cured resin of E-PPESK with number-average molecular weight 3962 meant the largest cross-linked extent in the polymer,and its appearance was also the best.The glass transition temperature(T_g)of the cured E-PPESK/DDE resin was 249℃.The results of tensile shear property test show that E-PPESK adhesives with number-average molecular weight 7570 has maximum value for both of PA 650(polyamide) and DDE as curing agents.Mixed the above-mentioned adhesive with E-51,the resulting adhesive with DDE as curing agents had maximum tensile shear strength up to 21.88 MPa when the dosage of E-51 was 25 phr.