Modification Of Benzoxazine Resin With Linear And Hyperbranched Polymers

In this thesis,four linear polyaryletherketones(PAEK)were synthesized via nucleophilic substitution reaction mechanism using bisphenol A,allyl bisphenol A,bisphenol AP and bisphenol fluorene as phenol sources.PAEK and hyperbranched polymers were blended with benzoxazine resins(BA-a,DDM)respectively.The differential scanning calorimetry(DSC)test technique was used to study the curing kinetics of each system and calculate the average apparent activation energy of each system.DSC and thermogravimetric analyzer(TGA)were used to study the curing behavior and thermal properties of the blends.The mechanical properties and fracture morphology of the blended resin were analyzed using a universal material testing machine,a drop hammer impact tester and a scanning electron microscope(SEM),respectively.The PAEK end groups contain active hydroxyl groups.Blending with benzoxazine resin can promote the benzoxazine ring-opening curing at low temperatures,thereby reducing the curing temperature of benzoxazines and it decreases as the amount of PAEK added increases.Among them,the poly(aryl ether ketone)side group molecular structure has a great influence on the ring-opening curing reaction of the oxazine ring,and the decrease in the curing temperature of the bisphenol-A poly(arylene ether ketone)(BA-PAEK)blend system is most pronounced,When the amount of PAEK added was 9%,the initial curing temperatures of BA-PAEK/BA-a and BA-PAEK/DDM resin systems decreased by 22 and 29°C,respectively,while the side groups contained allyl,phenyl and fluorene groups the initial curing temperature decreased by 14-24 and 5-24°C,respectively,indicating that the bulky side groups are not conducive to the ring opening of the oxazine ring.Using kissinger ozawa and starink as kinetic models,the apparent activation energy of curing reaction was calculated for each blend system.Among them,the BA-PAEK/benzoxazine resin system has the lowest apparent activation energy value,and the apparent activation energy value of the fluorene-based PAEK(BF-PAEK)/benzoxazine resin system is the highest.This result is consistent with the curing behavior.In addition,the addition of polyaryletherketone increased the T_g and impact resistance of the blended resin,and the toughness was improved.For the BA-a resin system,the thermal stability of the polymer is significantly improved,while the thermal stability of the DDM system changes little.Hydroxyl-terminated,carboxyl-terminated hyperbranched polyesters(H402,C102)and hydroxyl-terminated hyperbranched polyamides(HPN202)as benzoxazine resin-modified additives greatly reduced the initial curing temperature of benzoxazine resin by hydroxy,carboxyl,and secondary amine groups.Among them,when the addition amount of hyperbranched polymer was 9%,the curing temperature of C102 in BA-a and DDM systems decreased by 47 and 38°C,respectively,while that of HPN202 decreased by 13 and 14°C,respectively,and the decrease of H402 was lowest,only 8 and 12°C,indicating that the carboxyl group has the strongest ring-opening promoting effect on the oxazine ring,while HPN202 contains a secondary amine group and a synergistic effect of the terminal hydroxyl group,so the curing temperature is lower than H402.The introduction of hyperbranched polymers into the benzoxazine resin system greatly improves the T_g and impact resistance of the polymer.At the same time,the toughness of the polymer is greatly improved,and the thermal stability of the BA-a resin is significantly improved.However,for the DDM system,thermal stability has decreased significantly.