Research On The Aging Effects Of The Polyurethane Films In Extreme Ultraviolet And Ozone Environment

In this article, two kinds of polyurethane film material were studied under ultraviolet，ozone andUV/ozone comprehensive aging environment respectively. The film samples were prepared by spincoating, the aging experiment of the samples was carried in the independently developed agingequipment. The infrared spectrum situ test, color difference, yellowness index, UV-Vis spectra of thesamples in different aging time were recorded with FT-IR spectroscopy, colorimeter apparatus andUV-Vis spectroscopy respectively. Field emission scanning electron microscope(SEM) was used tocharacterize the microstructures of the films before and after the aging experiments.According to the infrared spectroscopy of the film samples during the aging process, thefunctional groups in the polyurethane molecule were investigated, and the photo oxygen index(PI)value and the carbonyl index(CI) value were caculated according to the formula. The results show thatthe infrared absorption intensity of methyl and methylene in the polyether polyurethane moleculedecreased with the aging time, while the infrared absorption intensity of hydroxyl group, amino groupand carbonyl group increased with the aging time, and C-O bond fractured; in polyester polyurethanemolecule, the infrared absorption intensity of the methyl and methylene, hydroxyl group, amino groupchanged a little with the aging time, and the infrared absorption intensity of the carbonyl groupdecreased with the aging time. The difference of the carbonyl change law between the two kinds ofpolyurethane was analyzed theoretically. In single UV environment, the PI and CI value of the twokinds of polyurethane appeared linear relationship with the aging time and increased with it at lowerUV intensity; while at higher UV intensity, the PI value and CI value increased quickly at the beginningand then slow down with the aging time; within the same aging time, the higher the UV intensity, thelager the PI value and CI value. In the single ozone environment, changes of PI value and CI valuerelatively decreased. While in the UV/ozone integrated environment, values of PI and CI showed asignificant increase.Analysis results of UV-visible absorption spectrum showed that the carbonyl region of200nm~300nm UV absorption band changed, the band intensity of polyether polyurethane increasedwith the aging time. In high intensity UV, high concentration ozone and UV/ozone synthesisenvironment, the band intensity increased rapidly at the beginning and then slowed down; the UVabsorption band intensity of polyester polyurethane appeared decreased in the later of the aging period. The test results of color difference and yellow index showed that polyether polyurethane weremore prone to yellowing than polyester polyurethane. The color difference and yellow index concertedresponse to environment factors.SEM tests found that the impact of UV and ozone on polyurethane morphology varies. The filmswere more likely to appear to rattle after UV aging while their surface appeared protrusions and cavitiesafter ozone aging. Under the comprehensive environment condition, the surface of polyurethane filmsshowed embrittlement with the emergence of chalking phenomenon.The synergistic effect of the two environmental factors of UV and ozone was analyzedcomprehensively, and the synergistic mechanism was discussed.