Huimin Cao,Xi Guo,Yongdong Zhou,Yutao Yan,Weisheng Sun
To improve the hydrophobicity of precious hardwood, a facile sanding pretreatment and alkyl ketene dimer (AKD) modification were performed. After the AKD modification, the wood was highly hydrophobic, and the contact angle was 143°. The increased hydrophobicity could be attributed to the ester bond formed between the wood hydroxyl groups and AKD, which was confirmed by attenuated total reflectance–Fourier transform infrared spectroscopy. Sanding pretreatment could further greatly increase the wood hydrophobicity and render it superhydrophobic, not only in a cross-section but also in the tangential and radial sections. The changed wood surface roughness could be responsible for the increased hydrophobicity, which was confirmed by characterization with a scanning electron microscope (SEM) and a three-dimensional optical microscope. Apart from the improved hydrophobicity, the AKD-modified wood exhibited excellent water, acid, and toluene resistance. After a 12 h immersion, the contact angle did not change significantly, and the acid immersion contributed to an improvement in the hydrophobicity of the wood. Furthermore, the resultant AKD-modified wood exhibited an excellent self-cleaning effect.
Increasing interest in 3D-printed high-performance polymers is observed due to their excellent mechanical properties and high resistance to chemical and thermal degradation. One of the ongoing challenges is to achieve sufficient joint strength because of the inertness of thermoplastics . In the current work, effects of surface treatment on shear bond strength of 3D-printed samples were focused and assessed. First, polyetherimide (PEI), polyether ether ketone (PEEK) and PEEK/CF(carbon fiber) as adherend were produced via FDM 3D printing . Then, sanding or atmospheric plasma treatments were carried out to improve the surface wettability of the 3D-printed specimens. Significantly, reduction in surface roughness was observed in sanding treated specimens, while nearly no change occurred in plasma-treated counterparts. However, surface free energy and wettability were greatly improved after plasma treatment. Single lap-shear tests and failure mode for PEI, PEEK and PEEK/CF using two different adhesives (film and liquid) were investigated, and the effect of surface treatment on bond strength was further compared. Results suggested that liquid adhesive contributed higher joint strength for surface-treated specimens in comparison to film adhesive . Besides, atmospheric plasma treatment is more efficient and safer method for 3D-printed PEEK and PEEK/CF, achieving a higher joining strength.
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