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In this study, hydroxyapatite (HA) was surface modified with silane coupling agent. The modified HA was named HA-APTES, and its structure was analyzed. Hydroxyapatite modified urea-formaldehyde resin (HUF) were prepared by adding different amounts of HA-APTES in the synthesis process. The properties of the resin were tested to determine the optimal addition amount of HA-APTES, and the thermal curing properties of resins were investigated by differential scanning calorimetry. The results suggested that HA-APTES has excellent formaldehyde-reducing effect and can significantly improve the wet shear strength of the resin, and the optimal addition amount of HA-APTES is 3%. Notably, compared to UF resin, the peak temperature and activation energy (Eα) of HUF resin are increased, the reaction sites are increased, and the network structure is complicated. [ABSTRACT FROM AUTHOR]

In this study, the prepolymers (TYF) were prepared by formaldehyde and l -tyrosine, different amounts of TYF were added to prepare TYF modified urea-formaldehyde adhesives (LUF), and the gel time of resin, formaldehyde emission and wet shear strength of the plywood were tested. This result indicated that the optimal addition amount was 3 wt%, and the formaldehyde emission of plywood decreased by 23% to 0.57 mg/L, and the wet shear strength increased by 47% to 1.47 MPa. The thermal degradation and curing characteristics of urea-formaldehyde (UF) and LUF resins were characterized by thermogravimetric (TG) and differential scanning calorimetry (DSC), and the kinetic parameters were analyzed. The results showed that TYF could reduce the formaldehyde emission and improve the wet shear strength significantly. Moreover, the thermal degradation activation energy (E α) of UF resin was increased, and the thermal stability was enhanced. Although the initial and peak curing temperatures of LUF were higher, but the LUF cured more easily than the UF once the curing temperature was reached. [Display omitted] [ABSTRACT FROM AUTHOR]

Soy-based adhesives are considered to be a substitute for toxic petroleum-based adhesives in wood industry because of its environmentally-friendly property. However, their application range is limited by the lack of high wet bond strength and high toughness. While it is possible to impart these properties to soy-based adhesives by adding a variety of corresponding modifiers, it is difficult to do so by adding a single modifier. In this work, a multifunctional cross-linking agent dodecanedioic acid diglycidyl ester (DADE) with high reactivity, toughening, and hydrophobic effects was synthesized and incorporated into soy-based adhesive to ameliorate the bonding performance of the adhesives. The reaction process between DADE and protein was confirmed by instrumental analyses. Results revealed that the introduction of 4% DADE increased the wet bond strength of the soy protein adhesive by 140% to 1.57 MPa, whereas the wet bond strength (1.11 MPa) of soybean meal adhesive containing 4% DADE was comparable to that of MUF resin. The micrographs of the fracture surface and the force-distance curves of the shear strength test showed that the toughness of the adhesives was significantly improved by DADE. These improvements were attributed to the long hydrophobic aliphatic chains and highly reactive groups from DADE. This modification method avoided using large amounts of chemical additives. This work may provide an efficient and low-consumption method for producing bio-based adhesives with excellent bonding properties. [Display omitted] • The resulting soy-based adhesive was an environmentally-friendly wood adhesive. • A multifunctional crosslinker with toughening and hydrophobic effects was developed. • The use of DADE avoided the addition of additional hydrophobic and toughening agents. • The strength of the SPD adhesive was higher than that of formaldehyde-based resin. [ABSTRACT FROM AUTHOR]

Soy protein-based adhesives are biodegradable and renewable and are widely used in wood based products. However, the application of soy protein (SP) adhesives is also limited by its poor mildew resistance, water resistance and bonding strength, so it is necessary to find ways to promote the comprehensive performance of SP adhesives. In this study, hydroxymethyl l -tyrosine (TYF) synthesized from l -tyrosine and formaldehyde was used to enhance the mildew resistance and bonding strength of the SP adhesive. The results showed that the cross-linking reactions of TYF and SP molecules and the condensation reactions between an appropriate amount of TYF molecules enhanced the force between SP molecules and made the cross-linked structure more stable and compact, resulting in a significant increase in the bonding strength of the SP adhesive modified by TYF. Compared with the plywood prepared by the SPI adhesive, the SP adhesive modified with 6 wt% TYF had the best bonding performance, and its dry and wet shear strength were increased by 49.3% and 110.1%, respectively. In addition, l -tyrosine Schiff base, which had antibacterial, bactericidal and antiviral effects, was produced by dehydration of TYF molecules, so the mildew resistance of SP adhesives modified by TYF was effectively enhanced. [ABSTRACT FROM AUTHOR]

Although soy protein (SP) adhesives have shown great potential in promoting the green and sustainable development of the wood industry, the practical application of SP adhesives is limited by poor performance (bonging strength, mold resistance and water resistance). Cross-linking modification is considered to be the most effective modification method for SP adhesives. In this work, non-antibacterial l -tyrosine (TYR) was treated with epichlorohydrin to graft multiple epoxy groups and transformed into tetraepoxy l -tyrosine (ETY). Interestingly, ETY exhibited obvious antifungal properties with a bacteriostatic rate as high as 98.3%. Adding a low amount (3 wt%) of ETY, the wet shear strength of the modified adhesive was 169.1% higher than that of the pristine SP adhesive, reaching 1.83 MPa. Moreover, in an environment of 28 °C and 80% humidity, both uncured and cured SP adhesives (with 3 wt% ETY) exhibited an anti-mold period of more than 30 days. Therefore, this work reveals that non-antibacterial bio-based materials may be endowed with antibacterial properties through epoxidation and transformed into multifunctional modifiers, and provides a new way for the development of high-strength antibacterial bio-based adhesives. • Non-antibacterial bio-based materials may be endowed with antibacterial properties through epoxidation. • The antibacterial rate of tetraepoxy l -tyrosine is as high as 98.3%. • High performance adhesive modified by low amount of ETY. • The wet shear strength of the adhesive (with 3 wt% ETY) increased by 169.1% to 1.83 MPa. • Modified adhesives (with 3 wt% ETY) showed an anti-mold period of more than 30 days. [ABSTRACT FROM AUTHOR]

Urea formaldehyde (UF) is the most widely used resin in the wood composite board industry. UF has formaldehyde emission, which is harmful to the environment and human health. In this paper, hydroxyapatite (HAP) was surface modified by silane coupling agent (HAP-KH). And hydroxyapatite/urea formaldehyde resin (HAP-UF) was prepared by adding different amounts of HAP-KH. The optimal amount of HAP-KH was determined by wet shear strength and formaldehyde release. The degradation performance and degradation kinetics of the resin were also studied. The results show that the addition of HAP-KH can improve the wet shear strength of plywood and reduce the release of formaldehyde. The optimal content of HAP-KH was 3%, and the formaldehyde emission of plywood reached the lowest level of 0.35 mg L−1, 52.32% lower than that of the control resin. The wet shear strength was 1.14 MPa, 14.4% higher than that of the control resin. HAP-KH had no significant effect on the thermal stability of UF resins. However, HAP-KH has a significant effect on the thermal degradation mechanism of UF resins. The most likely kinetics mechanism models for UF and HAP-UF are G(a) = [−ln(1−α)]2 and G(a) = [−ln(1−α)]3, respectively. [ABSTRACT FROM AUTHOR]