Oil release behavior and kinetics of oil-impregnated kapok fiber powder

In this study, kapok fiber powder (KFP) was evaluated as a wicking material for the application of mechanical lubricants. KFP had lengths ranging from several microns to 2 mm, with part of the hollow lumen being compressed. Experiments showed that the oil sorption capacity of KFP for mineral oil and PAO4 was 21.9 g/g, and 19.9 g/g, respectively. The oil release behavior of oil-impregnated KFP was quantitatively evaluated by a device proposed in the present study to simulate the usage of lubricant in bearings. The results indicated a two-step oil release process including a rapid release phase and a slow release phase. The cumulative oil release increased with an increasing oil/fiber ratio and temperature. The release mechanism of oil-impregnated KFP was further investigated by release kinetics models which demonstrated that the oil release followed Fickian diffusion and could be described by the Rigter–Peppas model. These results are proposed to provide a reference for the evaluation of the oil release performance of oil-impregnated wicking materials when they are applied in mechanical bearing field.