Zhang Jinyang, Su Chao, Rogers Fergus J M, Darwish Nadim, Coote Michelle L, Ciampi Simone
School of Molecular and Life Sciences, Curtin Institute of Functional Molecules and Interfaces, Curtin University, Bentley, Western Australia 6102, Australia.
Phys Chem Chem Phys. 2020 May 28;22(20):11671-11677. doi: 10.1039/d0cp01317j. Epub 2020 May 14.
Here, we investigate the development and relaxation of static charges on the surface of plastic materials that are first brought in contact, and then macroscopically separated. Experimentalists dealing with the static electrification of insulators are aware of difficulties predictably attaining, and precisely reproducing, a given charging magnitude. Here we have observed for the first time that in homo-systems (e.g. PTFE rubbed against PTFE) charge densities reach the maximum value after a material-specific contact time. Attempts to charge a sample beyond its peak value leads to a progressive drop in charge. We propose this drop to result both from the electrostatically driven segregation of polymer ionic fragments, as well as from the discharge of unstable fragments by dielectric breakdown when a sufficiently high surface charge density is reached. We therefore highlight the general existence of two branches in the charging versus charging time curve: the assumption of a monotonous charging slope holds only left or right of the charging maxima and to achieve a specific charge density, care has to be taken to remain within one branch. Differences between materials in the tribocharging peak time are shown to reflect difference in material transfer rates and water adsorption, rather than differences in electronic factors such as the relative stability of cationic and anionic fragments.
在此，我们研究了首次接触然后宏观分离的塑料材料表面静电荷的产生和消散情况。处理绝缘体静电起电的实验人员清楚，要可预测地达到并精确重现给定的充电量存在困难。在此我们首次观察到，在同系体系中（例如聚四氟乙烯与聚四氟乙烯摩擦），电荷密度在特定材料的接触时间后达到最大值。试图使样品充电超过其峰值会导致电荷逐渐下降。我们认为这种下降是由聚合物离子片段的静电驱动分离以及当达到足够高的表面电荷密度时不稳定片段通过介电击穿放电共同导致的。因此，我们强调在充电与充电时间曲线中普遍存在两个分支：单调充电斜率的假设仅在充电最大值的左侧或右侧成立，并且要达到特定的电荷密度，必须注意保持在一个分支内。摩擦起电峰值时间的材料差异表明，这反映的是材料转移速率和水吸附的差异，而不是诸如阳离子和阴离子片段相对稳定性等电子因素的差异。
