Aspects of the Safe Storage of Acrylic Monomers: Kinetics of the Oxygen Consumption

Abstract

Safe storage and handling of acrylic monomers assumes detailed knowledge about possible reactions and influence parameters on the radical polymerization. An investigation was made in order to predict the stability of the monomers by quantifying the oxygen consumption due to the inhibition process for different influence parameters. The oxygen consumption was investigated for acrylic and methacrylic acid without inhibitor as well as in the presence of p-methoxyphenol (package inhibitor) and phenothiazine (process inhibitor) in the temperature range from 40 to 80 C. The addition of stabilizer lowers the oxygen consumption in the monomers, which results in a higher stability. The oxygen consumption rates for unstabilized (up to 60 C) and p-methoxyphenol-stabilized monomers fit the Arrhenius equation and can therefore be extrapolated to other temperatures. The stability of the monomers at higher temperatures can be predicted with the help of the oxygen consumption rates (not for phenothiazine). At lower temperatures, slow polymerization rates can extend the stability of the monomer beyond the time of oxygen inhibition.

Oxygen Inhibition in Dental Resins

“…The inhibition resulting from oxygen diffusing from the atmosphere into curing resins is responsible for the inhibited surface layers commonly found on freshly polymerized unfilled resins (Finger et al, 1996;Vallittu, 1999;Yatabe et al, 2001). This is due to the oxidation of radicals into stable species known as peroxides (Reaction 1) (Andrzejewska et al, 1998;Schulze and Vogel, 1998), which have low reactivity toward monomers.…”

Influence of light-curing units on the polymerization of low-shrinkage composite resins

“…The highest DC in LS may be related both to the lowest AC and the cationic ring-opening process, which is insensitive to the existence of oxygen. In the free-radicalmediated polymerization process, oxygen inhibits further polymerization because it can inactivate free radicals by converting them into stable species (peroxides) 28,29) . In this process, fillers are also important.…”

Effect of Energy Density on Low-Shrinkage Composite Resins: Diode-Pumped Solid State Laser Versus Quartz-Tungsten-Halogen Light-Curing Unit

“…Actually, oxygen inactivates free radicals that are essential for the initiation of the methacrylatebased composite resins, by forming stable peroxides. 23,24 The existing or externally diffused oxygen inhibits further polymerization; therefore, reaching DC > 70% is not easy in composite resins. On the bottom surface, some cases showed a higher DC even with lower energy density.…”