A New Wood Adhesive Based on Recycling Camellia oleifera Cake-Protein: Preparation and Properties

Abstract

In order to improve the initial viscosity and stability of Camellia oleifera cake-protein adhesive, Camellia oleifera cake-protein was blended with defatted soybean protein (DSP), soybean protein isolate (SPI), and casein, followed by adhesive preparation through degradation and crosslinking methods. The performance of Camellia oleifera cake-protein adhesive was investigated by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), scanning electron microscopic (SEM), and thermogravimetric (TG) and X-ray diffraction (XRD). The results showed that DSP, SPI, and casein likely promoted the effective degradation of Camellia oleifera cake-protein, and, thus, more active groups were formed in the system, accompanied by more reactivity sites. The prepared adhesive had a lower curing temperature, and higher initial viscosity and stability, but the storage time was shortened. Moreover, DSP, SPI, and casein, themselves, were degraded into peptide chains with lower molecular weights; thus, improving the overall flexibility of the adhesive, facilitating a better elastic contact and regular array between crosslinking products, and further strengthening the crosslinked structure and density of the products. After curing, a compact and coherent reticular structure was formed in the adhesive layer, with both bonding strength and water resistance being significantly improved. According to the results obtained, the next step will be to study the DSP-modified Camellia oleifera cake-protein adhesive in depth.

Fully Bio-Based Adhesive from Tannin and Sucrose for Plywood Manufacturing with High Performances

“…The insoluble substance content was below 6% under both independent addition of tannin and sucrose, but when the tannin-sucrose mass ratio was 80:20 to 20:80, the insoluble substance content ranged from 62.4% to 76.9%. The insoluble substance content in the curing products of the tannin-sucrose composite adhesives significantly increased, proving the crosslinking reaction of tannin and sucrose [36]. Under the different mass ratios, the crosslinking degree and intensity of the cured adhesives were varied.…”

“…The adhesives were placed in tin foil and dried in a thermostatic ventilation oven at 60~70 • C [36]. Then, the adhesive was taken out, ground and passed through a 200-mesh sieve to obtain the adhesive powders (also used to test the curing performance of the tannin-sucrose composite adhesives).…”

A Composite Whole-Biomass Tannin–Sucrose–Soy Protein Wood Adhesive with High Performance

“…Similarly, a new crystallization peak was formed, and the crystallinity also increased after adding SPI, manifesting that the cross-linking degree increased, and the crystallinity was further improved by increasing the substitution ratio and curing temperature. However, the crystallinity at 33.3 • decreased somehow when the curing temperature was raised to 220 • C, because although high temperature was helpful to further improve the conversion of furanic compounds, the cross-linking degree and density of tannin and SPI were too high, which would reduce the crystallinity on the contrary [30,31,40]. In addition, the crystallinity of cross-linked products would also be reduced due to their decomposition at high curing temperature.…”

“…For the tannin-sucrose-SPI adhesive, long-chain SPI molecules were interspersed into the system to improve the overall flexibility of the adhesive, and the cross-linking structure and cross-linking density were further enhanced. The bonding layer of cured adhesive formed a dense and compact structure, and meanwhile, there was a better elastic contact and regular arrangement in the cured adhesive, which was more conducive to waterproof and the water resistance of the adhesive [7,36,40,46]. Due to the toughening effect of long-chain SPI, the over cross-linking of the tannin-sucrose adhesive system and the brittleness increase induced by water evaporation during hot pressing were relieved, and the degradation of bonding performance was avoided [47][48][49], macroscopically presenting good bonding strength and durability.…”