Research On The Modified Benzoxazine Resin

Benzoxazine resin is a new kind of heterocycle thermosetting resin, which developed onthe basis of traditional phenolic, and carries on the excellent properties of phenolic, such asthermal properties, flame resistence and electrical performance. At the same time benzoxazinehas no release of small molecules when curing and volume contraction is nearly zero.However, with the development of technilogy, the heat resistance of benzoxazine can notsatisfy the development of various fields, so the benzoxazine needs to be modified to improveits heat resistance.In this paper, a bisphenol-A based benzoxazine (BA-a) which assumed faint yellow andwell-proportioned particulate matter was synthesized at 80℃by the suspension method.945cm-1is the characteristic peak of BA-a by the fourier transform infrared spectroscopy(FTIR). The solubility of BA-a was measured and the experiment result suggests that theBA-a can dissolve well in general organic solvent such as acetone, trichloromethane and soon.In order to improve the heat resistance of BA-a further, Molybd-phenolic (Mo-PF), RTMbismaleimide (BMI) and moulded bismaleimide (BMI) which have excellent thermalproperties were employed to modify BA-a. The effect of different content and kind ofmodifier on the curing characteristics and thermal decomposition characteristics of themodified BA-a were researched.The gelation properties of BA-a and its modified system were measured. It was shownthat Mo-PF and moulded BMI decreased the gel time of the modified system effectively. Theapparent activation energy of every system was calculated based on the gel point. The resultswas following: the activation energy of the resin system modified by Mo-PF was lower thanthat of the pure benzoxazine resin and the activation energy of the other modified BA-a werehigher than that of the pure benzoxazine resin. The temperature-time equation and figure were obtained.The differential scanning caborimetry (DSC) was used to research the curing kinetics ofmodified benzoxazine resin. Kinetic triplet were calculated by Kissinger equation, Ozawaequation and Crane equation. The result shows that the activation energy of the BA-amodified by Mo-PF and RTM BMI (20%) were lower than that of the pure benzoxazine resinand the activation energy of the other modified BA-a were higher than that of the purebenzoxazine resin. The reaction order of modified benzoxazine were 1. At the same time thecuring process parameters were calculated by extrapolating T～βmethod.The thermal decomposition of modified BA-a was researched by thermogravimetricanalysis (TGA) with the non-isothermal model at nitrogen atmosphere. The result shows thatall modified system improved the char yield, thereinto the moulded BMI (content 30%)improved the char yield maximally (38 wt.%) and was 35% higher than pure BA-a resin. Theheat index of the modified system were higher than that of the pure BA-a resin (180.516℃),moreover the heat index of the modified BA-a by Mo-PF (206.486℃) was highest.