Irradiation Effects Of Electron And Vacuum Ultraviolet On PI Aerogel And CF/PTA Composite

In this paper,radiation tests were carried out for a PI aerogel(Polyimide aerogel)and a CF/PTA composite(Carbon fiber reinforced polytriazole composite)with the employment of high and low-energy electron radiation facilities and vacuum ultraviolet radiation equipment.The irradiation effects of electron and vacuum ultraviolet on the thermal stability,thermal conductivity,thermal diffusivity and bending strength of the PI aerogel and CF/PTA composite were investigated by using modern analysis techniques such as SEM,ATR-FTIR and XPS,and the related damage mechanism was discussed.Furthermore,the influence of electron or vacuum ultraviolet irradiation on the outgassing characteristics of these two materials were also examined by in-situ and post analysis techniques.The results show that the radiation of 170 ke V and 1 Me V electrons would cause ionization damage to the PI aerogel,leading to PI degradation and lower C-O bond content in the aerogel.In addition to the ionization damage,the 170 ke V electron radiation also induces the charge and discharge damage effect in the PI aerogel.The discharge damage might destroy surface morphology of the PI aerogel and reduce the specific surface area.The vacuum ultraviolet irradiation would result in activating of PI aerogel surface,and increase the content of O element and the ratio of C=O and C-O bonds.Electron irradiation and vacuum ultraviolet irradiation have limited effects on thermal stability,thermal conductivity and thermal diffusivity of the PI aerogel.The radiation of 170 ke V and 1 Me V electrons and vacuum ultraviolet radiation have been found to cause ionization damage in the CF/PTA composite,resulting in degradation of the polytriazole(PTA)matrix and decrease of the C-N bond content.With the increase of irradiation electron energy,the ionization damage effect of PTA matrix increases,and thus decreases the thermal stability and flexural strength of the composite.It is shown that 1 Me V high-energy electron radiation would remarkably reduce the thermal stability and flexural strength of the CF/PTA composite,while 170 ke V electrons and vacuum UV have little effect on the thermal stability and flexural strength of CF/PTA composite.The mass loss of PI aerogel and CF/PTA composite due to vacuum outgassing with time is found to conform to the exponential quasi first-order kinetic equations.170 ke V and 1 Me V electrons radiation would cause the PI aerogel to degrade,resulting in an increase in the mass of collected volatile condensable material(CVCM).And vacuum ultraviolet radiation would cause PI aerogel surface to activate,leading to reaction of PI aerogel with the adsorbed gases and thus reduction of the quality of CVCM.It is also found that both electron and vacuum radiation might increase the ex-situ total mass loss(TMLex)of CF/PTA composite,while the 1Me V electron radiation significantly increased the mass of CVCM.The in-situ dynamic test results show that the vacuum ultraviolet radiation would cause the surface activation of PI aerogel,leading to a significant decrease in the H2 O content in the gas environment,while the vacuum UV might cause the CF/PTA composite to degrade and release ions such as CH3+,C3H3+ and C3H5+,etc.