Contact electrification (CE), or the development of surface charges upon contact and separation, is a millennia-old scientific mystery and the source of many problems in the industry. Since the 18th century, efforts to understand CE have involved ranking materials according to their charging propensities. In all these reports, wood, an insulator, turns out to be surprisingly immune to CE. Here, we show that this unique antistatic nature of wood is attributable to its lignin content, i.e., lignin removal from wood ceases the antistatic property, and (re)addition brings it back. The antistatic action of lignin (also an insulator) is proposed to be related to its radical scavenging action and can be explained through the bond-breaking mechanism of CE. Our results also show that lignin, a sustainable, low-cost biopolymer, can be used as an antistatic additive in some representative examples of elastomers and thermoplastics, displaying the universal nature of its antistatic action.
Lignin is a complex 3D organic polymer, consist of hydroxyl, methoxyl, carbonyl and carboxyl substitutions without an exactly known chemical structure. Occurring in higher plants, mainly in woody tissues of hardwood and softwood plants, lignin is the world's second most abundant polymer which provides unique strength and elastic properties of the plants. Predominantly, lignin is obtained as a byproduct during the pulp production of the paper industry and millions of tons of lignin per year are mostly burned simply for energy. Such an abundant polymer also has some very useful features such as having antioxidant properties, being amorphous and behaving like thermoplastics. Thus, it is convenient to be used as a source of low molecular weight chemicals, dispersants, emulsifiers, and additives for polymeric materials. Since many industries such as polymer, electronics, space, medicine and etc. are dealing with troubles caused by static electric deposition; it is aimed, in this study, to provide a cheap and environment friendly method for avoiding electrostatic charge formation using lignin as an antistatic agent for elastomers. Elastomers doped with isolated natural lignin are characterized by various techniques and then, lignin doped samples are analyzed for surface charge density measurements (net charge and discharge time measurements) to assess the extent of antistatic behavior and the results are compared with the undoped samples.
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