Incorporation of guanidine and ethylguanidine into thermosetting resins

Guanidine- and arginine-containing proteins are commonly used in the manufacture of formaldehyde-based thermosetting resins; however, the polymer structures of these resins were not known. ¹³C-NMR spectroscopy has now been applied to demonstrate that guanidine does react and form crosslinks in formaldehyde reactions. Ethylguanidine was used to model arginine in soy proteins, and the NMR analysis indicates that guanidine side chains in proteins also react and form crosslinks in biobased adhesives. Furthermore, these reaction products change with pH demonstrating that the formation of desired polymer species can be controlled and optimized. Finally, the products of the two most widely manufactured amino resins, melamine-formaldehyde and urea-formaldehyde, were then compared with those of guanidine-formaldehyde and ethylguanidine-formaldehyde.