Investigation On Radiation Effects Of Poly (Ether Ether Ketone) Under Complicated Conditions

Poly(ether-ether-ketone)is an aromatic organic thermoplastic polymer with excellent properties such as high melting point,chemical corrosion resistance,hydrolysis resistance,friction resistance and radiation resistance.It is widely used in aerospace,electronic information,energy,machinery,automobile and other fields.Ionizing radiation under complex irradiation conditions leads to cracking,cross-linking and oxidation reaction of PEEK.It can not only destroy performances of PEEK component,but also reduce the operating reliability of device and shorten the service life of device.Investigation on the radiation effect of PEEK at high-temperature oxidizing atmosphere and evaluation of effect of radiation aging on performance of PEEK provides a scientific basis for predicting the service life of PEEK components.In the paper,the species,quantity and evolution of free radicals in EB-irradiated PEEK before and after thermal annealing were analyzed by ESR method,and the effects of oxygen content,temperature and absorbed dose on the chemical structure,oxidation degree,melting behavior,thermal stability and crystalline structure of the EB-irradiated PEEK were also studied.The contents and results were as follows:(1)The PEEK powders and films with the different sizes were irradiated by electron beam in air and in oxygen respectively.The radical species and quantities in the PEEK after irradiation and thermal annealing were analyzed by ESR.Phenoxy and peroxyl radicals were mainly produced in the PEEK samples irradiated in air and in oxygen.The concentration of free radicals increased gradually with absorbed dose.The concentration of free radicals in the samples irradiated in oxygen was lower than that in air.After annealing at 50-250oC,the concentration of free radicals in the samples irradiated in air decreased gradually with the increase of temperature.Interest was concentration of free radicals in the samples irradiated in oxygen firstly increased and then decreased with the increase of temperature.After annealing at 300~oC for different time,the ESR spectra was measured at room temperature,indicating that phenoxy radicals produced,and the amount of the phenoxy radicals was no significant change with the elongation of annealing time.Owing to the decomposition of more peroxides,the concentration of the phenoxy radicals in the samples irradiated in oxygen was higher than that in air.(2)Effects of oxygen content,irradiation temperature and absorbed dose on performances of the EB-irradiated PEEK were studied in detail by characterization methods such as FT-IR,XPS,DSC,TGA,XRD and so on.The oxidation degree of PEEK increased with the increase of oxygen content,temperature and absorbed dose.It showed that not only the absorption peak intensity of carbonyl and aryl ether bonds in the infrared spectra increased,but also the O/C ratio of the PEEK samples in the calculated XPS results rised,and the thermal stability,melting temperature and crystallization temperature of the samples decreased in TGA and DSC results.However,the intensity and location of characteristic X-ray diffraction peaks of the PEEK samples did not change significantly before and after radiation,indicating that irradiation had no obvious effect on the crystal structure.In the dose range of500-4500 kGy,the water contact angle decreased with the increase of absorbed dose,suggesting that the increase of oxide on the surface of the PEEK films.The tensile fracture stress and elongation at break of the PEEK films firstly increased and then decreased with the increasing absorbed dose because of the predominant radiation cross-linking in PEEK samples in the low dose,and the overwhelming radiation cracking in the high dose.