Spectroscopic studies of the polymerization of anaerobic adhesives

Date of Completion

January 2001


Chemistry, Polymer




Anaerobic adhesives cured by a redox initiated free radical mechanism have been known in industry for over two decades. A typical formulation contains monomer, stabilizers, accelerators, a fluorophore used as an inspection aid, and various other ingredients to modify polymer properties and rheology. Conventional technology for in situ characterization is difficult to apply to anaerobic polymerization due to the unique requirements of this system. These include exclusion of oxygen, narrow bond gaps, and the presence of a transition metal. By taking advantage of the presence of the fluorophore and working within the constraints of the system, a new cure monitoring method has been developed. The application of UV-Vis spectroscopy has shown that the absorption of the fluorophore does not change during polymerization implying that it does not participate in the process. Fluorescence spectroscopy in contrast, has shown that collisional quenching of the fluorophore occurs in the presence of an amine that is commonly used as a cure accelerator. By monitoring the change in fluorescence, room temperature reactions have been characterized. In addition, the same quenching mechanism has been used to calculate activation energies. Polymerization results also show excellent correlation with FTIR techniques. ^