Study on surface creation and wettability of bamboo through abrasive belt sanding

In manufacturing bamboo products, sanding is an important method to make surface modification. In this study, mechanical sanding experiments were carried out to investigate the resultant surface creation and wettability. Electrostatic sand-planting abrasive belts with meshes of P60, P80, P120 were selected as abrasive tools. Dimensional bamboo strips were used to prepare workpieces with wax layer and pith film completely removed. Here, we carefully considered structural characteristics of bamboo, including internode and node areas at bamboo skin (BS) and pith ring (BP) sides. Dynamic contact angles were measured to evaluate surface wettability. In contrast with the unsanded surfaces, contact angles of sanded bamboo surfaces significantly declined at the end moment of 12s. Interestingly, node areas at BS and BP sides basically exhibited lower contact angles after sanding than internode areas. Surface morphology is a key component of surface creation, the impact of which on the wettability was studied. Specifically, mechanical sanding caused noticeable plowed ridges and much micro-fibrillation, leaving anatomical cavities like fractured vessels and pits exposed. Surface roughness was measured by a non-contact 3D profilometer with parameters of Sa, Ssk, Sku, Str, Sdr, Spc. The quantitative analysis presented that the Sa and Sdr values of sanded surfaces can be sorted as P60 > P80 > P120. Importantly, the results indicate that a rougher bamboo surface with greater Sa does not definitely result in better wettability. Detailed information on surface creation should be taken into account.