(551f) Experimental and Theoretical Investigation of Photopolymerization Using a Narrow Channel Reactor

Increasing applications of polymers in a variety of fields has demanded the improvement in processing methodologies in the manufacturing sector. Increasing demand for energy efficiency has triggered active research in exploiting field effects for carrying out reactions. One of the field effects that have been widely exploited is us of ultraviolet (UV) radiation. UV initiated polymerizations carried out in stirred tanks suffer poor penetration depth and usually end up with broad molecular weight distribution (MWD) due to inefficient mixing. The majority of photopolymerization on thin films have been limited to curing applications where mixing is absent. This work investigates the use of UV radiation for carrying out free radical polymerization in a continuous flow system. The concepts of process intensification have been thoroughly applied to enhance the reaction rates by reducing the path lengths.

This study involves UV initiated homopolymerization of butyl acrylate and styrene using a simple continuous narrow channel flow reactor. Results from this work were benchmarked against thermal polymerization carried out in microreactors and in batch. A mathematical model has been developed to aid understanding of the process. The model also incorporates the channel geometry in the kinetic expression.

The influence of process parameters such as initiator concentration, flow rate, and light intensity on the conversions and molecular weight distributions will be reported. Polymerization was carried out in a narrow channel glass reactor (di=1.5mm) using UV intensity in the range of 50-150 mW/cm^2. 2,2-dimethoxy-2-phenyl-acetophenone was used as initiator. The monomers studied were butyl acrylate and styrene. Gas Chromatography was used to monitor the conversion and gel permeation chromatography for the MWD. The findings from this work are currently being used by the process intensification research group at Clarkson University to develop and evaluate the performance of several intensified reactors for polymerization processes.