The development of formaldehyde-free functional wood
composite
materials through the preparation of strong and multifunctional soybean
protein adhesives to replace formaldehyde-based resins is an important
research area. However, ensuring the bonding performance of soybean
protein adhesive while simultaneously developing thermally conductive
adhesive and its corresponding wood composites is challenging. Taking
inspiration from the microphase separation structure of spider silk,
boron nitride (BN) and soy protein isolate (SPI) were mixed by ball
milling to obtain a BN@SPI matrix and combined with the self-synthesized
hyperbranched reactive substrates as amorphous region reinforcer and
cross-linker triglycidylamine to prepare strong and thermally conductive
soybean protein adhesive with cross-linked microphase separation structure.
These findings indicate that mechanical ball milling can be employed
to strip BN followed by combination with SPI, resulting in a tight
bonded interface connection. Subsequently, the adhesive’s dry
and wet shear strengths increased by 14.3% and 90.5% to 1.83 and 1.05
MPa, respectively. The resultant adhesive also possesses a good thermal
conductivity (0.363 W/mK). Impressively, because hot-pressing helps
the resultant adhesive to establish a thermal conduction pathway,
the thermal conductivity of the resulting wood-based composite is
10 times higher than that of the SPI adhesive, which shows a thermal
conductivity similar to that of ceramic tile and has excellent potential
for developing biothermal conductivity materials, geothermal floors,
and energy storage materials. Moreover, the adhesive possessed effective
flame retardancy (limit oxygen index = 36.5%) and mildew resistance
(>50 days). This bionic design represents an efficient technique
for
developing multifunctional biomass adhesives and composites.