High-Performance Resin Formulations with Ozone-Pretreated Corn Cob Lignin and Lysine

Nontoxic resins formulated with renewable components have been receiving increased attention as sustainable alternatives to petroleum-based resins. In this work, we demonstrate a new class of lignin-amino acid (LA) resins, formulated with nontoxic components that are abundant and can be renewably sourced from field leftovers (corn cobs) and lysine (from biobased sugars). NMR (1H, 31P, 13C–1H HSQC, 15N–1H HSQC, and 15N–1H HMBC), FTIR, thermogravimetric, gel permeation chromatography, and elemental analyses provide insights into the physicochemical properties of the resins, including the presence of LA linkages such as C–N cross-linking. The LA resin creates strong bonds between pieces of wood, metals (aluminum and stainless steel), and plastics. Internal bond strengths (IBSs) of balsa wood and medium density fiberboard specimens glued with LA resins, measured using an Instron instrument, were comparable to those bonded with commercial polyurethane and polyvinyl acetate resins. Resins prepared with ozone-pretreated lignin have significantly larger molar masses and display increased bond strengths with glued substrates as inferred from IBS measurements. This is attributed to the creation of reactive oxygen-based functionalities in the lignin upon ozone pretreatment. LA resins thus show promise as a feasible and sustainable alternative to petroleum-based resins.