Revealing the Interface Structure and Bonding Mechanism of Coupling Agent Treated WPC

Abstract

This paper presents the interfacial optimisation of wood plastic composites (WPC) based on recycled wood flour and polyethylene by employing maleated and silane coupling agents. The effect of the incorporation of the coupling agents on the variation of chemical structure of the composites were investigated by Attenuated total reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) and Solid state 13C Nuclear Magnetic Resonance spectroscopy (NMR) analyses. The results revealed the chemical reactions that occurred between the coupling agents and raw materials, which thus contributed to the enhancement of compatibility and interfacial adhesion between the constituents of WPC. NMR results also indicated that there existed the transformation of crystalline cellulose to an amorphous state during the coupling agent treatments, reflecting the inferior resonance of crystalline carbohydrates. Fluorescence Microscope (FM) and Scanning Electron Microscope (SEM) analyses showed the improvements of wood particle dispersion and wettability, compatibility of the constituents, and resin penetration, and impregnation of the composites after the coupling agent treatments. The optimised interface of the composites was attributed to interdiffusion, electrostatic adhesion, chemical reactions, and mechanical interlocking bonding mechanisms.

Improvement of White Spruce Wood Dimensional Stability by Organosilanes Sol-Gel Impregnation and Heat Treatment

“…The wood chemical characterization was obtained from FTIR spectra and NMR 13 C and 29 Si spectra. FTIR spectra were recorded between 4000-400 cm −1 , at 4 cm −1 of resolution using 64 scans.…”

“…Indeed, ethanol could solubilize some wood extractives (polyphenols) [26], leading to a decrease of certain peaks on the infrared spectrum compared to heat-treated wood only. Figure 4 shows the 13 C NMR and 29 Si spectra of oven dried wood, non-treated and treated with organosilanes (OWSSiHT).…”

“…The C2, C3, and C5 of hemicelluloses are present in the peak at 75 ppm, and those of cellulose are present in the peak at 72.8 ppm. The C6 of crystalline cellulose and C5 of hemicelluloses For 29 Si spectra (Figure 4), the non-treated wood spectrum shows no peaks due to the absence of silica in the wood. MTMOS signals in the 29 Si NMR spectrum are at -37 and -39 ppm [30].…”

“…The C6 of crystalline cellulose and C5 of hemicelluloses For 29 Si spectra (Figure 4), the non-treated wood spectrum shows no peaks due to the absence of silica in the wood. MTMOS signals in the 29 Si NMR spectrum are at -37 and -39 ppm [30]. The organosilane-treated wood spectrum does not show these peaks, which means that no MTMOS remained unreacted.…”

“…The C6 of crystalline cellulose and C5 of hemicelluloses have a peak at 65.0 ppm. The C6 amorphous of cellulose is presented in the peak at 63.0 ppm [27][28][29]. The peaks from lignin are present at 173.1 ppm for the carboxyl groups, 148.1 ppm for the C4 carbon atoms, 132.8 ppm for the aryl group, 89.2 ppm for the βO4 and αO4 bond of lignin, and 56.4 ppm for the carbon from the methoxyl groups of lignin.…”