ISSN   1004-0595

CN  62-1224/O4

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2种纤维素纳米纤维作为水基润滑添加剂的摩擦学性能研究

Tribological Properties of Two Cellulose Nanofibers as Water-Based Lubricant Additives

  • 摘要: 为探索不同制备方法得到的纤维素纳米纤维作为水基润滑添加剂的摩擦学性能,选择TEMPO (2, 2, 6, 6-四甲基哌啶-1-氧自由基)氧化法和机械法得到的2种纤维素纳米纤维(TO-CNF和C-CNF). 采用光学显微镜(POM)、扫描电子显微镜(SEM)、激光粒度仪、红外光谱(FT-IR)、X射线粉末衍射(XRD)和元素分析等方法对其形貌和结构进行表征,发现上述2种不同类型的CNF均为棒状结构,且为纤维素I型,其中氧化法制备的TO-CNF结构中含有一定量的羧基官能团. 通过热重分析表明,C-CNF的热稳定性略优于TO-CNF. 进一步通过UMT往复摩擦试验机研究了2种CNF作为水基润滑添加剂的摩擦学性能,结果表明,在添加量(质量分数,w)不超过1%时,2种CNF在不同添加浓度下均表现出显著的减摩性能. 其中TO-CNF的减摩性能略优于C-CNF,添加w=1%可使摩擦系数相对于基础体系降低51%. 通过钢板表面接触角和磨损后的表面分析对CNF的润滑作用机理进行分析,推测由于CNF结构中含有大量的羟基或羧基等极性官能团,作为添加剂能够在摩擦副表面发生不同程度的吸附从而形成润滑保护膜,防止滑动表面微凸体的直接接触进而改善摩擦学性能.

     

    Abstract: In order to explore the tribological properties of cellulose nanofibers obtained by different preparation methods and their potential as water-based lubrication additives, a thorough analysis was conducted. This study focused on two types of cellulose nanofibers (CNF) variants: TO-CNF and C-CNF obtained by TEMPO (2, 2, 6, 6-tetramethylpiperidine-1-oxyl radical) oxidation and mechanical methods respectively. To gain insights into the morphology and structural characteristics of these CNFs, several analytical techniques were employed. Optical microscopy (POM) allowed for the initial visualization of the surface properties of these cellulose nanofibers, offering a macroscopic perspective. Subsequently, scanning electron microscopy (SEM) was harnessed, capitalizing on its capacity for high-resolution imaging. SEM unearthed the minute intricacies of these nanofibers, unveiling their structural intricacies. In addition to visual inspection, the structural constituents of these cellulose nanofibers were probed using Fourier-transform infrared spectroscopy (FT-IR) and X-ray powder diffraction (XRD). FT-IR was instrumental in detecting specific functional groups within the nanofibers, with particular emphasis on the presence of carboxyl groups. XRD findings unveiled vital insights into the crystalline arrangement of both TO-CNF and C-CNF. It was discerned that both variants featured rod-shaped structures and were classified under the cellulose I category. Notably, TO-CNF obtained through oxidation exhibited a perceptible quantity of carboxyl functional groups. Beyond structural characterization, the thermal stability of these CNFs was meticulously scrutinized, given its paramount significance in potential applications as lubrication additives within high-temperature environments. The outcomes of our investigation unveiled that C-CNF showcased marginally superior thermal stability compared to TO-CNF, a noteworthy attribute that could augment their performance in demanding conditions. Frictional properties of both types of CNF as water-based lubricant additives were studied by reciprocating friction tests using the UMT tribometer. The results proved highly promising. Both TO-CNF and C-CNF exhibited exceptional anti-friction properties when introduced at concentrations not exceedingw=1%. In fact, they demonstrated remarkable anti-friction capabilities across a spectrum of concentrations. It was noteworthy that TO-CNF showcased slightly superior anti-friction performance in comparison to C-CNF. For instance, the inclusion ofw=1% TO-CNF led to a remarkable 51% reduction in the friction coefficient when juxtaposed with the base liquid. These findings underscore the substantial potential of CNF in augmenting the lubrication performance of water-based systems, rendering them an enticing prospect for a gamut of industrial applications. The lubrication mechanism of CNF was analyzed by investigating surface contact angles and post-wear surface analysis of steel plates. It was speculated that the polar functional groups in the CNF structure, such as hydroxyl or carboxyl groups, could adsorb to the surface of the friction pair in different degrees as additives, forming a lubricating protective film to prevent direct contact of sliding surface asperities and improve frictional properties. To sum up, the continued research endeavors and optimization of CNF as lubrication additives might potentially lead to more efficient and eco-friendly industrial applications, thereby addressing the critical requisites across diverse industries.

     

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