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Ultrahigh molecular weight polyethylene (UHMWPE) is suitable for tribological applications in various environments because of its advantageous characteristics, including its high‐impact strength, excellent resistance against wear and corrosion, and self‐lubricating properties. However, the tribological behavior of UHMWPE under seawater lubrication is still poorly understood. In this study, the wear mechanisms of UHMWPE in seawater environment were elucidated by examining its morphology and structural evolution during sliding friction. The tribological properties of UHMWPE were significantly affected by the sliding speed in seawater. At low sliding speeds, no long‐strip structures were observed on the worn UHMWPE surface. However, as the sliding speed was increased, prominent convex long‐strip structures appeared and became more densely distributed with time. The molecular chains in the amorphous region of UHMWPE stretched along the sliding direction under stress. In the crystalline region, molecular orientation, and lamellar slip were accompanied by molecular conformational transformations. During the initial stage of sliding friction, UHMWPE mainly exhibited adhesive wear caused by plastic deformation. Subsequently, the wear mechanism of UHMWPE gradually changed from adhesive wear to a combination of adhesive and abrasive wear, and its wear intensified over time. [ABSTRACT FROM AUTHOR]

Polymer materials possess low density, high strength, corrosion resistance, and excellent cavitation erosion resistance. As a result, they are widely used in marine, water conservancy, and other engineering equipment as replacements for metal materials. However, polymer friction pairs working in a water environment for an extended period are easily damaged by cavitation erosion. In this work, the cavitation behavior of polytetrafluoroethylene (PTFE) and ultra-high molecular weight polyethylene (UHMWPE) in deionized water and seawater is investigated through experiments and computational fluid dynamics (CFD) simulations. The results indicate that the cavitation erosion resistance of UHMWPE is significantly better than that of PTFE, and the UHMWPE has four cavitation process stages, while the PTFE has only three cavitation stages. 316 L counterparts in the seawater corrosion and cavitation coupling effect of a large number of metal particles off and wash polymer material surface, so that the cavitation erosion of PTFE and UHMWPE is more serious in seawater environment. CFD simulation demonstrates that the cavitation erosion zone under the radiator shows a semicircular distribution. Meanwhile, the formation of ring-shaped cavitation pit is related to the distribution of bubbles on the surface of the radiator. The cavitation rate of PTFE and UHMWPE is slowed down by the "water cushion effect." [ABSTRACT FROM AUTHOR]

In this work, blended composites with ultra‐high molecular weight polyethylene (UHMWPE) as matrix polymer, α‐zirconium phosphate (α‐ZrP) as filler, and sodium polyacrylate (PAANa) as compatibilizer were prepared. The interfacial interaction between PAANa as a compatibilizer and the components of α‐ZrP/UHMWPE was studied by molecular dynamics simulation. The friction and wear behavior of the GCr15 ball/composite friction pair under seawater lubrication under different loads were explored, and the friction and wear mechanism were analyzed. The results show that PAANa as a compatibilizer can effectively improve the interfacial interaction force between components of PAANa/α‐ZrP/UHMWPE composites. The composites exhibited different trends regarding the relationship between tribological properties and α‐ZrP content under various loads. The wear mechanism of composites under low load is mainly represented by extrusion deformation. With the increase of load, the wear mechanism of composites gradually changed into adhesive wear and abrasive wear (depending on the content of α‐ZrP). This work provides a theoretical basis for preparing and applying other α‐ZrP/polymer blend composites. [ABSTRACT FROM AUTHOR]

Using thermal‐oxidative aging and tribological experiments, effects of thermal‐oxidative aging processes on tribological properties of polyformaldehyde (POM) and ultra‐high molecular weight polyethylene (UHMWPE) were evaluated and compared with each other. It was found that the color of UHMWPE surface after aging has turned to yellow, while that of POM surface has no obvious change. The aging factors lead to dimensional change of UHMWPE disk specimens from the original circle to the ellipse in the meantime. Tribological experiments show that friction coefficients of the pairs of POM/GCr15 and UHMWPE/GCr15 tend to decrease after thermal‐oxidative aging, and the decreasing tendency in friction coefficients of POM/GCr15 is more distinct. The results of this study will contribute to the understanding of the relationship between aging and tribological properties of POM and UHMWPE, and enrich the theory of polymer tribology. [ABSTRACT FROM AUTHOR]

Abstract: As oxidation stability of engine oil was hard to evaluate in field, this paper tried to propose a field test method to determine the oxidation onset temperature (OOT) of gasoline engine oil. A theoretical model of grey average value of oil spot image and OOT was established by using spot test method, image processing, and Pressure Differential Scanning Calorimetery method. The oil sample unknown OOT was taken to spot test and image processing in field to obtain the grey average value. The OOT can be calculated by bringing the grey average value to the established theoretical model. This approach was successfully used for OOT determination of 4 different kinds of engine oils with good accuracy and precision. The absolute error of mineral oils was less than 4.52°C, and synthetic oils were less than 1.2°C. This convenient, low‐cost, and reliable method can achieve OOT of engine oil in field determination and provide reference for engine oil drain interval evaluation. [ABSTRACT FROM AUTHOR]

ABSTRACT Ultraviolet aging restricts the outdoor application of polyformaldehyde as the friction material. In this work, ultraviolet aging processes were applied to polyformaldehyde specimens and effects of the processes on their surface properties and tribological performance were evaluated. Surface morphology results show that a thin layer of white powder and micro-cracks with further ramifications in other directions were observed on the surfaces after 400 h of ultraviolet exposure, while it is not detectable for the unaged specimens. Analysis of aging surface indicates that ultraviolet leads to the increase of micro-cracks and the degree of crystallinity. All the tribological test results demonstrate that with the extension of ultraviolet aging time, (i) the process of damage on polyformaldehyde surface induced by ultraviolet aging is first slowly and faster afterward; (ii) the fluctuation of the friction coefficients of polyformaldehyde/GCr15 rubbing pairs increases; and (iii) the wear rate of polyformaldehyde markedly increase after aging test 400 h. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44684. [ABSTRACT FROM AUTHOR]