Study On Modification Of Bismaleimide With Soluble Polyimide Oligomers

In this paper,4,4'-(hexafluoroisopropylene)diphthalic anhydride(6FDA)and 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride(?-ODPA)are used as the acid anhydride source,the diaminodiphenyl ether as an amine source,two novel bismaleimide resin systems were synthesized using one-step method,namely 6FPIO and?-BMI,respectively.The basic structure of the structure was analyzed by FT-IR?GPC and X-ray diffraction(XRD).The solubility of the new bismaleimide resin system was determined.The results showed that the number average molecular weights of the two bismaleimide resin systems were 1712 and 1682,respectively.And the synthesized polyimide oligomer has certain solubility in acetone.In order to improve the toughness of the cured product of bismaleimide resin system,the synthesized bismaleimide resin was added as a modifier to the conventional bismaleimide resin(4-4-bismaleimide diphenylmethane,BMI).The effects of different modifier content on gel time,viscosity-temperature relationship,curing reaction and mechanical properties of the traditional bismaleimide resin system were studied.The gel properties of 6FPIO/BMI and?-BMI/BMI resin systems were determined by the plate knife method,and the reaction activation energy of each system was calculated.The results showed that the reaction activation energy of the modified system was lower than that of the pure BMI resin system.With the increase of modifier content,the reaction activation energy of the modified bismaleimide resin system tends to increase.The viscosity characteristics of different modified systems were measured by the rotational viscometer.As the content of modifiers increased,the flow activation energy of the resin system continued to decrease.From formula 1 to formula 4 and formula 5 to formula 8,the activation energy of the resin system was measured.They are 61.27 kJ/mol,65.91 kJ/mol,69.33 kJ/mol,74.71 kJ/mol and 57.54 kJ/mol,63.49 kJ/mol,67.03 kJ/mol,and 72.91 kJ/mol,respectively.The non-isothermal differential scanning calorimetry(DSC)was used to study the curing reaction kinetics of the modified bismaleimide resin system.The reaction activation energies were calculated using Ozawa-Flynn-Wall and Friedman-Reich-Levi,respectively.And the Malek two-parameter model was used to determine the pre-exponential factor and reaction progression of the resin curing system,and the corresponding curing models were established.Using artificial neural network and genetic algorithm,the curing behavior of the modified bismaleimide resin system was fitted and analyzed.According to the fitting result,the hidden layer structure of the thermal neural network is determined as a double-layer structure with 15neurons.The number of iterations in a genetic algorithm is 50,the crossover probability is 40%,and the mutation probability is 5%.The fitting result is well fitted with the experimental curve,and the full error is less than 5%The tensile strength,flexural strength and impact toughness of the cured bismaleimide resin were tested by universal testing machine.The morphology of the port was analyzed by SEM,and the toughening mechanism was analyzed The results showed that the mechanical properties of cured resin system were the best when the modifier content was 20%.The tensile strength,bending strength and impact strength of 6FPIO/BMI and?-BMI/BMI resin systems were 82.87 Mpa,147.68 MPa,27.83 kJ/m~2?82.73 Mpa,144.66 Mpa,23.07 kJ/m~2,respectively.