One-Pot Biomass Formaldehyde-Free Phenolic Resin

Phenol-formaldehyde resins have long been used as coatings and adhesives in composite materials such as particleboard and plywood. But the discovery of the carcinogenic effects of formaldehyde has prompted chemists to seek out formaldehyde-free formulations. Yongsheng Zhang, Zhongshun Yuan, and Chunbao Xu of Western University, in London, Ontario, not only have come up with a phenol-furfural resin as an alternative, but demonstrate a straightforward process for preparing and curing the resin (AIChE J. 2015, DOI: 10.1002/aic.14716). The team used chromium/tetramethylammonium salts to catalyze conversion of glucose to hydroxymethylfurfural (HMF) and then copolymerized HMF with phenol in the same reaction vessel. Furthermore, hexamethylenetetramine (HMTA), which is commonly used to cure phenolic resins via alkyl cross-linking, is also a chemical of concern because it decomposes into ammonia and formaldehyde. The researchers instead turned to the compounds in solubilized lignin as an alkylating curing agent. Overall, the biobased resins have a structure similar to novolac phenol–formaldehyde resins and form fiberglass-reinforced composites comparable in strength with typical HMTA-cured phenolic resins.