Carbohydrate-hydroxymethylfurfural-amine adhesives: Chemorheological analysis and rheokinetic study

Carbohydrates as a component in adhesive formulations have been reported for many years. A rapid cure at moderate temperatures is a remaining challenge in the development of renewable adhesives. Rheology provides insight into all stages of structure formation of a cured polymer. This work analyses the curing of carbohydrate-amine adhesives with and without the addition of 5-hydroxymethylfurfural (HMF) as a biomass-derived key reactant in adhesives. Isothermal and non-isothermal rheological measurements were performed to characterize i) the rheology of the prepolymer, ii) the initial stages of curing, iii) the sol-gel transition, and iv) general rheokinetics. The viscosity profile was described by empirical models and showed a deviation from homogeneous curing. Rheokinetic analysis using isoconversional methods and Arrhenius plots showed that HMF reduces the activation energy of the curing reaction. The addition of 5 mol.-% HMF (based on starting fructose content) increases the reactivity by lowering the activation energy of the curing.

Automated summary

This study analyzed the curing process of carbohydrate-amine adhesives with and without 5-hydroxymethylfurfural (HMF), a key reactant in biomass-derived adhesives. The addition of HMF was found to reduce the activation energy of the curing reaction, thus increasing reactivity. Rheological measurements provided insights into the structure formation of the cured polymer and showed a deviation from homogeneous curing in the viscosity profile.