In this article, activation energies for a poly(methyl methacrylate) material were determined by shear rheometry and by bond strength in welding. Functions for temperature dependency of viscosity and for bond strength, depending on time and temperature, were found. These functions were fitted to measurements from shear rheometry between 230 and 270 A degrees C and from strength of lap-shear joints welded from 105 to 130 A degrees C, where by values of activation energies were found. It was found that bonding pressure was less than significant. Despite experimental differences, there was good correlation with data from literature for each method as well as for temperature dependency.