An evaluation of the effectiveness of continuous thin film processing in a spinning disc reactor for bulk free-radical photo-copolymerisation

Abstract This paper reports on UV-initiated free-radical copolymerisation of vinyl acetate with n -butyl acrylate (VAc-BA) under conditions of thin film flow in a spinning disc reactor (SDR). Almost 40% overall monomer conversion can be achieved in under 5 s under optimised operating conditions in the SDR, with controlled molecular weight properties of the copolymer, highlighting the good levels of mixing in the film. Residence time on the SDR is a limiting factor in the extent of conversion achievable in a single pass. Comparison with a static film demonstrates the superiority of the SDR in maintaining a high overall rate of polymerisation. Composition of the copolymer formed in the SDR indicates that, due to its plug flow behaviour, the SDR cannot address the inherent problem of compositional drift. We have shown that efficiency of light absorption is dictated by conditions favouring longest UV exposure times, rather than thinner films on the disc. Initiator decomposition efficiency, an important consideration in the overall rate of the co-polymerisation, is enhanced by lower fluid flowrates. This study highlights the promising technology offered by the SDR in combination with UV irradiation for the exploitation of photo-copolymerisation as a viable method for bulk copolymer synthesis.

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