Abstract: In a process for crosslinking a polymer, a .beta.-dicarbonyl functionality is present as a reactive diluent and/or as a reactive solvent and/or on a crosslinking entity. The .beta.-difunctional compound reacts with formaldehyde which is either released during the crosslinking reaction (or otherwise present) whereby less formaldehyde is released, than would otherwise be released. The formaldehyde which reacts with the .beta.-dicarbonyl compound is either incorporated into the crosslinked polymer network or released in the form of a reaction product which is not as harmful to the environment as the unreacted formaldehyde. The process enables the reduction of formaldehyde release during crosslinking to levels otherwise unobtainable. Furthermore, the process enables a reduction in the amount of organic solvent utilized.