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低温等离子体在聚合物材料表面改性方面有着广泛的应用。为了研究等离子体改性对材料表面一系列性能的影响,文中采用大气压空气中介质阻挡放电(dielectric barrier discharge,DBD)产生低温等离子体处理低密度聚乙烯(low density polyethylene,LDPE)薄膜,利用水接触角测试仪、傅里叶变换红外光谱仪(fourier transformed infrared spectroscopy,FTIR)和表面电位测试系统等对改性表面进行分析。实验结果表明:在处理的前20 s内,随着处理时间的增加水接触角显著降低。继续增加处理时间,水接触角变化趋于饱和。FTIR测试结果表明DBD处理后LDPE薄膜表面引入了羰基类含氧极性基团。表面电位三维分布图表明,DBD处理后的LDPE表面电位衰减比未处理的快,并且随处理时间增加,衰减率提高。导致上述结果的原因有两方面:第一是水接触角降低引起表面吸附水分含量提高,增大材料的表面电导率,提高了表面载流子的迁移速率,加快电荷沿面消散。第二是DBD处理在LDPE薄膜表面生成了羰基等极性基团,引起表面陷阱能级变浅,表面入陷的电荷更容易脱陷。总之,重频脉冲DBD处理能够有效地加快LDPE薄膜表面电荷的消散,可以为应用提供参考。
Low temperature plasma has a wide range of applications in the surface modification of polymer materials. In order to study the effect of plasma modification on a series of properties of the material surface, a low density polyethylene (LDPE) thin film was formed by atmospheric pressure plasma dielectric barrier discharge (DBD) Contact angle tester, fourier transformed infrared spectroscopy (FTIR) and surface potential test system to analyze the modified surface. The experimental results show that the contact angle of water decreases significantly with the increase of treatment time in the first 20 s. Continue to increase the processing time, the change of water contact angle tends to be saturated. FTIR test results showed that the carbonyl-type oxygen-containing polar groups were introduced into the surface of LDPE film after DBD treatment. The three-dimensional distribution of surface potential shows that the surface potential of LDPE after DBD decay is faster than that of untreated LDPE, and the decay rate increases with the increase of treatment time. There are two reasons for the above-mentioned results. The first one is the decrease of water contact angle, which leads to the increase of moisture content on the surface, increasing the surface conductivity of the material, increasing the surface carrier transport rate and accelerating the charge dissipation along the surface. The second is that DBD treatment generates polar groups such as carbonyl groups on the surface of the LDPE film, causing the surface trap level to be shallow and the trapped surface charge to be more easily detached. In summary, the repetition rate pulse DBD treatment can effectively accelerate the dissipation of the surface charge of the LDPE film, which can provide reference for the application.