Kinetic study of the crosslinking of gelatin by formaldehyde and glyoxal

A study has been made of the effect of concentration of the crosslinking agent, gelatin concentration, and pH on the rate of increase of viscosity with time, for gelatin solutions containing either formaldehyde or glyoxal. The results are consistent with the kinetic relationship: For formaldehyde, n is 2. For glyoxal, n is 1, as was expected for this bifunctional hardener. Initial formation of gelatin–methylol compounds is proposed in both cases. With formaldehyde, it is suggested that this leads to a methylene‐ether crosslink between a gelatin amino‐methylol compound and an unspecified gelatin–methylol compound, while in the case of glyoxal, there is evidence to suggest that the crosslinkage involves two side‐chain amino groups and results in a charged crosslink.