Some aspects of free radical polymerisation in UV-curing

Abstract

Various quinoxalines,in association with N-methyld-iethanolamine as synergist, were used to initiate the polymerisation of acrylates. It was found that the quinoxalines where used with amine synergist are efficient Type II initiators. It was also found that the cure of the acrylate is faster when oxygen is present in the reaction mixture than when it is absent.The photoinitiating efficiency of 2-Methyl-1-[4-(methylthio)phenyl]-2- morpholinopropane-1-one (IRG-907) was compared to different initiators using RllRspectroscopy and N-Isopropylmorpholine(IPM) was used as a model to investigate the properties of the morpholino sustit.uent present in IRG-907. It was shown by RTIR spectroscopy, photocalorimetry,bulk polymerisation and the curing of thin films that 1PM acts as a physical quencher for the triplet state of IRG-907 and that it is a very poor hydrogen donor. Sensitisation of IRG-907 by lix was also investigated and it wasconfirmed that lix can sensitise the -cleavage of 1RG907. Photoinduced fragmentation of aminoalcohols by quinoxalines are discussed and the reactivity of the aminoalcohols reflect their ability to undergo electron transfer and to fragment.A wide range of aminoalcohols were synthesised and used as synergist in the polymerisation of a number of acrylates using different methods and the photoyellowing and photooxidation of aminoalcohols were also investigated.Some mixed acrylate-cinnamate systems were prepared to investigate a new dual cure system.The conversion percentage was found to be very low.The lack of cure is probably due to the cinnamates are scavenging the benzoyl radicals