An eco-friendly and high shear strength adhesive from catechol-modified polyethyleneimine

Conventional adhesives often emit volatile organic compounds (VOCs), which have a negative impact on human health. In this paper, an environmentally-friendly supramolecular adhesive PD which has high adhesive and low VOCs emission is prepared by the reaction between polyethyleneimine (PEI) and 3,4-dihydroxybenzaldehyde (DBA). PD containing abundant catechol groups exhibit excellent adhesion to wood substrates and is able to reach a maximum shear strength of 5.20 +/- 0.39 MPa. One factor is attributed to multiple reactions between PEI, and DBA and oxidation of DBA. These reactions construct a complex three-dimensional cross-linked structure which is very helpful to improve the bonding performance of the adhesive. Another reason refers to the fact that a large number of catechol groups in PD can form a lot of hydrogen bonds with the amino group in PEI and the hydroxyl group in the wood substrate. These hydrogen bonds play an important role in enhancing shear strength. PD adhesives have a stronger bond strength than commercial chloroprene rubber (CR, Pattex-PXL) and polyvinyl acetate adhesives (PVAc, JUJU-8708) and have lower emissions of VOCs. As an environmentally-friendly adhesive for wood-based substrates, this adhesive may have potential applications in the wood processing industry. Conventional adhesives often emit volatile organic compounds (VOCs) because of using toxic raw materials in the production and these VOCs have a negative impact on human health. In this paper, a series of adhesives with low VOCs emission and high shear strength are prepared from 3,4-dihydroxybenzaldehyde and polyethyleneimine by a reaction which has produced Schiff base.image