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The purpose of this paper is to study, analyze and present the lubricating mechanism and tribological properties of two types of oil‐based titanium complex grease containing Polytetrafluoroethylene (PTFE).

Two types of oil‐based sebacic acid/stearic acid titanium complex greases containing PTFE additive were synthesized using 3 L reaction vessel, and the base oils including neopentyl polyol ester and mixed oil of 650SN and neopentyl polyol (1:1.8). Friction‐reduction, antiwear, and load‐carrying properties of greases were evaluated using a four‐ball tester, and their dropping point and penetration were characterized using relevant ASTM standards. Morphologies of wear scar and chemical states of typical elements on worn surfaces were characterized by means of scanning electron microscope and X‐ray photoelectron spectroscopy, respectively.

Tribological results show that titanium complex grease containing PTFE had better friction‐reduction and antiwear properties than base grease. However, PTFE could not improve the load‐carrying capacity of base grease. Moreover, a synergistic effect between deposited film and adsorptive film contributes to good tribological properties of titanium complex grease.

Such a very useful lubricating material could be used in industrial applications including steel plants, power plants, packaging, and fertilizer industries.

The lubricating mechanism of titanium complex grease containing PTFE was proposed by tribochemical analysis of worn surfaces. The mechanism should become the direction of the theoretical and applied research of grease in the future.

Little attention has been given to the effects of returnee entrepreneurs on external and internal corporate social responsibility (CSR). This study aims to investigate whether returnee entrepreneurs engage in more external or internal CSR and to further explore the contingency effects of foreign market embeddedness and local government endorsement.

This study uses 11,967 startups in China to examine the relationship between returnee entrepreneurs and external and internal CSR. The authors use an ordinary least square regression and propensity scoring matching approach to analyze the data.

The empirical results show that returnee entrepreneurs are more likely to undertake external CSR but less likely to undertake internal CSR. Foreign market embeddedness and local government endorsement have opposite moderating effects on these relationships.

This study has important implications for returnee entrepreneurs’ strategic choice between external and internal CSR and also provides theoretical support for policymakers to make effective and enforceable CSR policies.

This study discusses how returnee entrepreneurs implement external or internal CSR in China, answering the call to distinguish between external and internal CSR. Drawing on a legitimacy perspective, the authors find interesting and seemingly counterintuitive effects of returnees on external and internal CSR, which also necessitates distinguishing between these two types of CSR. In addition, the authors find different moderating roles of foreign market embeddedness and local government endorsement.