Study On Ultraviolet And Electron Irradiation Effects On Novastrat-PI And UHMW-PE Poluethylene Films

In this paper,solar ultraviolet simulation equipment and high-energy electron accelerators are used to carry out 250-400 nm ultraviolet and 1 Me V electron irradiation experiments on transparent Novastrat-PI and UHMW-PE films.Summarize the changes of spectral transmittance and tensile properties of two materials under irradiation conditions.Using FTIR,XPS to explore the irradiation damage mechanism of the two thin film materials.The test results show that Novastrat-PI film has better radiation resistance than UHMW-PE film.Ultraviolet irradiation has little effect on the performance of PI film,and its spectral transmittance and tensile properties show a slight downward trend as the irradiation time increases.After the irradiation reached 2000 ESH,the maximum transmittance decreased by 1.88%,and the tensile strength and elongation decreased by 24 MPa and 33.72%,respectively.The effect of 1 Me V electron irradiation on the performance of PI film is greater than that of ultraviolet irradiation.When the irradiation fluence reached 5E16 cm-2,the maximum transmittance decreased by 5.1%,and the tensile strength and elongation decreased by 43 MPa and 45.80%,respectively.After 2000 ESH UV irradiation,the PE film changed from milky white to light yellow.The maximum transmittance of PE film is reduced by 3.1%,the tensile strength and elongation are decreased by 10.6 MPa and 22.25%.After 1E16 cm-2 fluences,the color changed the same as that of ultraviolet irradiation,its transmission,tensile strength and elongation decreased by 7.3%,28 MPa and 88.53%,respectively.The FTIR and XPS results shows that the PI film has a stable molecular structure,and UV irradiation only destroys chemical bonds with low binding energy such as alicyclic C-C*,amide ring C-N and ether bond C-O bond.The main chain structure remains basically intact.The broken bond makes the lipid ring and amide ring partially destroy,and forming free radical or other reaction products,which has can influence on optical and mechanical properties.Because 1Me V electron irradiation is more easily break bonds than UV irradiation,so it can cause much defects in materials and more serious damage to materials.When PE films under irradiation,C-C fracture leads to molecular degradation,and C-H bond fracture may lead to inter chain cross-linking.After ultraviolet radiation,free radicals and C=C unsaturated groups are generated on the surface,which reduces the transmittance,and the local cross-linking slightly increases the yield strength and decreases the elongation.When irradiated with 1 Me V electrons,two effects of degradation and cross-linking occur simultaneously in the molecular chain of the PE film.In the initial stage of irradiation,the cross-linking effect between the chains is better than the degradation of molecular chains,which causes the strength of the material to increase.As the irradiation progresses,the cross-linking reaches saturation and degradation gradually dominates,causing the material strength to begin to decline after reaching an extreme value,and finally the mechanical properties are almost completely lost.Degradation and cross-linking can only occur in the movable segment,so the more crystalline phases in PE,the weaker the radiation degradation and cross-linking effect,the more stable the material.