重频脉冲放电等离子体处理聚合物材料加快表面电荷消散的实验研究

Experimental Study of Accelerating Surface Charge Dissipation on Polymer Treated by Repetitively Pulsed Discharge Plasmas

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 plasmas have been widely used in surface modification of polymer material. To study a series of performances on polymer treated by plasma, non-thermal plasmas generated by dielectric barrier discharge（DBD） are used to treat low density polyethylene（LDPE） films in atmospheric air. The results were analyzed with water contact angle measurement, fourier transformed infrared spectroscopy（FTIR） and system of surface potential measurement. The results show that water contact angle gradually decreased with increasing treatment time during 0~20 s. However, theirs values did not change obviously during 20~240 s. FTIR show that LDPE films after treatment formed oxygen-containing polar species such as carbonyl. Threedimensional distribution of the surface potential show that the process of decay was accelerated after DBD treatment. The decay rate improved with increasing treatment time. The results were explained for two aspects： one reason was that the reduction of water contact angle resulted in increasing of adsorption water content on the surface. It would increase surface conductivity and accelerate charge carriers to migrate along the surface. Another reason was that DBD treatment introduced polar carbonyl group on the surface, leading to the energy level of surface trap shallow. In summary, DBD generated by repetition frequency pulse can effectively accelerate surface charge dissipation of LDPE films. This can provide a reference for applications.