UV Curing in Carbon Dioxide

摘要

The photoinitiated radical polymerization of acrylate resins has been shown to proceed more rapidly and more extensively in a carbon dioxide atmosphere than in the presence of air. Due to the higher density of carbon dioxide gas, compared to air and nitrogen, CO_2 can be handled in open containers. This offers the opportunity for additional economic applications of the UV technology especially for 3D UV curing and small series production. Polymerization profiles, recorded by real-time infrared spectroscopy, demonstrated the clear advantage of working in an inert atmosphere, especially if only a few micron thick coatings are exposed to UV radiation. The detrimental effect of O_2 inhibition was shown to depend on a number of factors, such as the O_2 concentration in the atmosphere, the sample temperature, the resin viscosity, the resin reactivity, the film thickness, the concentration of photoinitiator, the light intensity and the radiation wavelength. Whereas the oxygen inhibition can be commonly overcompensated by high exposure doses, CO_2 inerting was required for achieving an effective surface cure of poorly reactive formulations exposed to UV light of low intensity.