A Theoretical and Experimental Study of Oil Wicking Mechanism of Kapok Fibrous Powder Assembly

Kapok fiber has a large lumen with a natural waxy surface which endows it with distinct hydrophobic-oleophilic properties. Oil-impregnated kapok fibrous powder (KFP) has great potential as a lubricant carrier material. To study the oil wicking mechanism of KFP assemblies with different pore structures (interfibrous pores and the lumens), a dual-scale model was established based on Washburn capillary theory. The theoretical model was verified by capillary rise test of KFP assemblies in various packing densities ranging from 0.08 g/cm3 to 0.14 g/cm3. It was found that the experimental results have good consistency with theoretical values at low packing densities. The deviation between the experimental result and the theoretical value increases with the increase of packing density. This can be largely attributed to compression of the lumens at increased packing density, leading to the reduction of oil sorption capacity within the lumens. The outcomes of this research are believed to provide important references for the usage of fibrous powder materials as lubricant carrier.