The Research Of Kinetics Of UV Photopolymerization In Super Low Temperature

Photocuring technology was a process that transformed a reactive liquid into a solid by radiation. Photopolymerization was used in coating, printing inks, adhesives, and biological applications such as dental restoratives, restorative bond materials. The broader the applications of photopolymerization were, the deeper the researches of the properties of photocuring were. The problem of volume shrinkage would happen during the photopolymerization process that turned the liquid into solid instantly. Volume shrinkage was restricted by many areas for it affected modality and mechanical properties of the polymer. On the other hand, the temperature was an important factor which influenced the properties of photocuring. Many researchers had investigated the curing above the room temperature.In this thesis, Near-IR technique was used to investigate the postcuring characteristic of acrylates which polymerized from -75℃up to room temperature. The effects of concentration of photoinitiator, structure of photoinitiator, structure of monomer on conversion of double bond and behavior of postcuring at low temperature were studied. The volume shrinkage of photopolymerization at low temperature was also studied. The electron spin resonance (ESR) technology was used to measure the living time of free radical in the system. The obtained results showed that free radical was alive in a period time after ceasing irradiation in free radical polymerization. The double bond conversion increased with the increase of the initiator concentration. The chemical structure of monomer and photoinitiator had great effect on the post cure process. Post cure was much more striking for the sample cured at lower temperature. The reduction of temperature was in favor of decreased volume shrinkage of free radical polymerization. 1,6-hexanediol diacrylate (HDDA) was crystal-state below -10℃, the cured product was also the crystal-state and could undergo post curing process.