Sustainable\nStarch-Extracted Amylose-Rich/Tannic Acid\nAdhesives with Robust Adhesion Properties on Wood Substrates

Presently, a wide range of commercial wood adhesives\nare formaldehyde-based\nand derived from petroleum resources, causing major environmental\nconcerns. The urgent requirement to minimize the production of formaldehyde,\nwhich can have damaging consequences for living organisms, has necessitated\nthe development of eco-friendly adhesives derived from biobased sources.\nThis study presents a novel, eco-friendly wood adhesive using amylose\n(AM) extracted from biobased starch (ST). The isolation of starch\nyields two distinct components, AM and amylopectin (AP). The use of\nthe isolated AM-rich component, in conjunction with tannic acid, a\nnatural polyphenolic compound, results in the formation of a formaldehyde-free\nadhesive derived from natural products through simple blending, without\nthe need for additional cross-linking agents. The adhesive forms as\nthe AM-rich solution recrystallizes via hydrogen bonding, creating\na double helix structure and resulting in a hydrogel with a three-dimensional\nnetwork. TA infiltrates the AM matrix, reducing matrix crystallinity\nby lowering interchain hydrogen bonding, which enhances adhesion by\ndecreasing viscosity and increasing penetration and spreadability\ninto wood pores. In addition, the AM-rich/TA adhesive formed a robust\nhydrogen bond with the wood substrate by the polyphenol present in\nTA, showing higher bonding strength and adhesion strength than the\nwood itself, supporting a weight of up to 23 kg. The phenolic moieties\nof TA exhibit good antibacterial and antimildew properties. Therefore,\nthe multifunctional AM-rich/TA hydrogel is a sustainable and environmentally\nfriendly adhesive with superior adhesion properties. This sustainable\nmaterial offers a practical substitute for petroleum-derived adhesives\nand addresses the environmental concerns associated with their use.