Novel Low-Temperature Chemical Vapor Deposition of Hydrothermal Delignified Wood for Hydrophobic Property

Abstract

As a hydrophilic material, wood is difficult to utilize for external applications due to the variable weather conditions. In this study, an efficient, facile, and low-cost method was developed to enhance the hydrophobicity of wood. By applying the low-temperature chemical vapor deposition (CVD) technology, the polydimethylsiloxane-coated wood (PDMS@wood) with hydrophobic surface was fabricated employing dichlorodimethylsilane as the CVD chemical resource. The result of water contact angle (i.e., 157.3°) revealed the hydrophobic behavior of the PDMS@wood. The microstructures of the wood samples were observed by scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) analysis verified PDMS successfully coated on wood surfaces. The chemical functional groups of the PDMS@wood were investigated by Fourier transform infrared (FT-IR) and Raman spectra. The thermogravimetric results indicated the enhanced thermal stability of the wood after PDMS coating. In addition, the stability test of PDMS@wood indicated that the hydrophobicity properties of the PDMS@wood samples were preserved after long-time storage (e.g., 30 days). The scratch test was carried out to examine the abrasion resistance of the hydrophobic coatings on PDMS@wood surface. It was suggested that low-temperature CVD process could be a successful approach for fabricating hydrophobic wood.

Keywords: dichlorodimethylsilane; hydrophobic; low-temperature chemical vapor deposition (CVD); polydimethylsiloxane (PDMS); wood.

Figure 1

Schematic illustration of description of the entire process.

Figure 2

Low-temperature chemical vapor deposition (CVD) treatment of wood. (A) The device set-up of the treatment and (B) illustration of the formation of PDMS on the wood surface, including (I) moisture deposition onto the wood surface, (II) introducing C₂H₆SiCl₂ vapors onto the wetted wood surface, and the (III) the formation of PDMS though the (C) chemical reactions.

Figure 3

FT-IR spectra of untreated wood and PDMS@wood.

Figure 4

Raman spectra of the untreated wood, PDMS, and PDMS@wood.

Figure 5

Thermogravimetric curves of untreated wood, PDMS, and PDMS@wood: (A) TG and (B) DTG.

Figure 6

The SEM images of wood samples on tangential section: (A,B) untreated wood; (C,D) PDMS@wood.

Figure 7

The EDS analysis of wood samples on tangential section (A) untreated wood and (B) PDMS@wood.

Figure 8

The SEM images of wood samples on cross section: (A,B) untreated wood; (C,D) PDMS@wood.

Figure 9

The EDS analysis of wood samples on cross section (A) untreated wood and (B) PDMS@wood.

Figure 10

The water CAs of PDMS@wood on cross section. The different reaction temperature with durations of (A) 0.5 h, (B) 1 h, and (C) 1.5 h. The comparison of CAs at (D) initial and (E) equilibrium after 60 s.

Figure 11

The water CAs of PDMS@wood on tangential section. The different reaction temperatures with durations of (A) 0.5 h, (B) 1 h, and (C) 1.5 h. The comparison of CAs at (D) initial and (E) equilibrium after 60 s.

Figure 12

The dynamic SA test of PDMS@wood.

Figure 13

(A) Poplar cross section CA after 30-day storage. (B) Poplar tangential section CA after 30-day storage.

Figure 14

Abrasion resistance of PDMS@wood. (A) Schematic of the illustration of the sandpaper abrasion test. (B) The SEM image of the PDMS@wood surface before abrasion test. (C) The SEM image of the PDMS@wood surface after abrasion test. (D) The water CA and SA as a function of number of abrasion cycles for hydrophobic wood surface.