Study On The Synthesis And Performance Of Autocatalytic Phthalonitrile Resin

Phthaliconitrile resin(PN),as a new type of thermosetting resin,exhibits excellent heat resistance,flame retardancy and good mechanical properties,and has great application potential in the aerospace field.The structure type and filling amount of the curing agent have a great influence on the performance of the cured product,and the brittleness of the resin cast body is great,which restricts the development and application of PN resin.Therefore,the research on nitrile-based resins,especially those with self-curing ability,has important academic value and engineering significance.In this paper,resorcinol and tetranitrophthalonitrile are used as raw materials for nitrile resins,potassium carbonate is used as a catalyst,and 4-(3-hydroxyphenoxy)is synthesized by nucleophilic substitution reaction by adjusting the ratio of reactants.Phthalonitrile(DPH)and4,4’-(1,3-phenylene bis(oxy))diphthalonitrile(BPH)two nitrile-based resins,using infrared to analyze the blended resin It is confirmed that DPH contains-OH group,and BPH does not contain-OH group.Through the blending process,the blended phthalonitrile resins with different ratios of BPH and DPH were prepared,and cured at 370°C to obtain the cured product.Using infrared to analyze the blended resin before and after curing,it was found that DPH/BPH blended The phthalonitrile resin system undergoes a cross-linking reaction to form a self-curing nitrile-based resin material system.Further analysis revealed that the-OH group in DPH reacted with the-CN group in the blend resin to cross-link the two nitrile-based resins to form a longchain heterocyclic structure.This reveals that the self-curing mechanism of the blended resin is the crosslinking reaction initiated by-OH in the nitrile-based resin structure.In order to further clarify the curing behavior of DPH/BPH blended phthalonitrile resin,DSC was used to analyze the blended resin system and the Kissinger and Ozawa methods were used to obtain the activation energy,index factor,Reaction order: The Starink method is used to obtain the curing reaction activation energy change trend with the degree of curing,and the T-β extrapolation method is used to predict the theoretical curing temperature of the DBPH resin.In the study,the thermal stability and mechanical properties of self-curing nitrile-based resins with different blending ratios and different curing temperatures were analyzed and characterized.The results show that when DPH:BPH is 3:7 and curing temperature is 320 ℃,the overall performance of the prepared DPH/BPH blend resin is the best.T5% temperature is472.36 ℃,T10% temperature is 534.29 ℃,and carbon residue rate is 800 ℃.It is 68.24%,the glass transition temperature(tanδ)is 373 ℃,the tensile strength is 37.19 MPa,the bending strength is 72.23 MPa,the compressive strength is 207.45 MPa,and the elongation at break is0.82%.The reason for the pyrolysis weight loss of the blended resin was analyzed by infrared.Using polyether ether ketone and DPH/BPH resin to be blended and modified,the study found that PEEK did not cross-link with the nitrile-based resin during the curing process of the DBPH resin,but the strength and plasticity of the nitrile-based resin were improved,and the heat-resistant temperature was improved.And the residual carbon rate is reduced.When the PEEK content reaches 7 wt.%,the tensile strength of the cured DBPH resin is 47.41 MPa,the elongation at break is 1.12%,and the bending strength is 83.01 MPa,which are 27.5%,36.5%and 14.9% higher than the matrix resin respectively;DBPH /PEEK system T5% temperature is439.74 ℃,T10% temperature is 503.85 ℃,and the carbon residue rate of 800 ℃ is 59.23%,which are respectively reduced by 6.91%,5.70% and 13.2% compared with the matrix resin.Based on the microscopic analysis,it is shown that the toughening methods of PEEK to DBPH resin are the bridging restraint effect and the crack anchoring effect.The crack will bend between the toughened particles,forming a secondary crack,absorbing more damage energy,and inhibiting the further propagation of the crack.