(519b) Photo-Polymerization of Butyl Acrylate Using a Narrow Channel Reactor

Introduction

The
aim of this investigation is to study the kinetics of photopolymerization in a narrow channel reactor. A detailed
study on the influence of initiator concentration, flow rate, and light
intensity on the conversions and molecular weight distributions will be reported
in comparison to static film studies (1). This data is being currently used by
the process intensification research group at

Clarkson University to develop and evaluate the performance of several
intensified reactors for polymerization processes.

Background

Some of the distinct advantages of photopolymerization are: better control of the reaction
(initiation can be stopped by blocking the radiation), and high reaction rates
can be obtained at room temperature (2). UV-initiated polymerizations carried
out in stirred tanks suffer poor penetration depth and 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. In a narrow channel reactor, fluid
is well mixed by the shear effects (3, 4) which will improve the initiator
efficiency. Thus, narrow channel reactors are being investigated for photopolymerizations.

Description

Photopolymerization of n-butyl acrylate (BA) in a
narrow channel glass reactor (d_i=1.5mm) has
been carried out using UV intensity in the range of 50-150 mW/cm².
2,2-dimethoxy-2-phenyl-acetophenone is used as
initiator. Gas Chromatography was used to monitor the conversion and gel
permeation chromatography for the MWD. Comparisons will be made to thermally
initiated polymerizations carried out in micro-reactors in regard to the MWD
(3). A brief investigation into the penetration depth of the radiation will also
be addressed.

The
current study involving homopolymerization of BA will
be followed by copolymerization with styrene and vinyl acetate. The findings of
this research will aid in the understanding of phoopolymerization kinetics and for exploiting other
intensified modules.

References

1. Thin film solvent-free
   photopolymerization of n-butyl acrylate. I. Static film studies.     Boodhoo, K. V. K.; Dunk, W. A. E.; Jassim, M. S.; Jachuck, R. J.;
   Journal of Applied Polymer Science 
   (2004),  91(4),  2079-2095.
2. Photopolymerization
   Fundamentals and Applications. Scranton, A. B.; Bowman, C. N.; Peiffer, R. W.; ACS Symposium series 673.
3. Free Radical
   Polymerization in Microreactors. Significant
   Improvement in Molecular Weight Distribution Control. Iwasaki, T.; Yoshida, J. I.; Macromolecules (2005),
   38(4), 1159-1163.
4. A New Synthetic Method for
   Controlled Polymerization Using a Microfluidic
   System.
   Wu, T.; Mei,
   Y.; Cabral, J. T.; Xu, C.; and Beers, K. L.; Journal
   of American chemical society (2004), 126, 9880-9881.