Durable wood adhesives from furfural-based diols, diamines, and diisocyanates

The objective of this research was to use components derived from furfural to develop new adhesives for wood and to improve the adhesives that are currently in use. Furfural is available from renewable resources and offers an alternative source of adhesives.; Urea-formaldehyde resins were modified with 2,5-bis(hydroxymethyl)furan (BHMF) and 5-hydroxymethylfurfural. These resins were characterized by differential scanning calorimetry and used to construct plywood or particleboard. The mechanical properties of the composite wood products were not improved by the addition of the modifiers. In fact, high levels of modifiers lead to reduced performance of the composite wood products constructed therefrom. Particleboards constructed using resins modified with low levels of BHMF just prior to spraying the resin onto the particles were characterized by slightly reduced emissions of formaldehyde when compared to samples constructed from unmodified resins. In addition, the reactants in the urea-formaldehyde-BHMF system were examined using differential scanning calorimetry. Results indicate that BHMF does not react appreciably under basic conditions, but readily reacts under acidic conditions at pH values below 3.0.; Resins based on {dollar}5,5spprime{dollar}-ethylidene difurfurylisocyanate (EDFI) and {dollar}5,5spprime{dollar}-ethylidene difurfurylamine (EDFA) were also studied. Flakeboards constructed using EDFI were compared to those constructed using diphenylmethane diisocyanate (MDI, a commercially available wood adhesive). The flakeboards constructed using EDFI met or exceeded industry standards and were equivalent in performance to those constructed using MDI.; Flakeboards were also constructed using resin systems based on EDFI and MDI to which various modifiers had been added, including EDFA, BHMF, and a variety of natural proteins. Differential scanning calorimetry was used to characterize these resin systems. Flakeboards constructed from the systems based on EDFI with the various modifiers were characterized by improved performance relative to the samples constructed using EDFI in the absence of modifiers.; The synthesis of EDFI from EDFA was examined using triphosgene (a solid substitute for phosgene gas). Triphosgene can be used to effect the phosgenation reaction. Yields of the isocyanate were highest when a solvent was employed. Impurities (by-products formed by side reactions) were reduced when high temperatures {dollar}(100spcirc{dollar}C) were utilized.