Low‐weight fractions of graphene and hydroxyapatite enhance mechanics in photocured methacrylate adhesives

Abstract

In many applications, it is desirable for photocured adhesives to have high‐mechanical strength in the cured state, but relatively low viscosity when liquid. This was achieved by adding less than 0.5 wt% hydroxyapatite and graphene to methyl methacrylate with diurethane dimethacrylate (UDMA‐MMA). Nanoindentation shows hardness increasing by 30–40% and indentation modulus by >30% compared to UDMA‐MMA on its own. Rheometry shows only a small increase in uncured viscosity for the liquid state. The additives affect the optical properties, mobility of free radicals, photocuring, and degree of conversion, the effects of which are seen in Fourier transform infrared and micro‐Raman spectra. Thermographic images taken during curing show that the additives impact the photocuring process. In addition, changes in intermolecular bonding are seen in the vibrational spectra when the additives are present. The enhanced mechanical properties are attributed to the observed changes in photocuring and bonding.