Polymerisation of vinyl monomers in continuous-flow reactors. An experimental study, which includes digital computer modelling, of the homopolymerisation of styrene and methylmethacrylate by anionic and free radical mechanisms respectively in continuous flow-stirred-tank reactors.

摘要

An introduction is given to the background theory andudscientific literature of the major subject areas of interest inudthis thesis, namely the chemistry of free radical and anionicudpolymerisation, molecular weight control in each type of polymerisation,udpolymerisation reactors, computer simulation ofudpolymerisation processes and polymer characterisation by geludpermeation chromatography.udA novel computer model has been devised, based on theudanalysis of the polymerisation process in terms of the reactionudextent of each reactant and the use of generation functionsudto describe the concentration of living and dead polymericudspecies, for the free radical, solution polymerisation of methylmethacrylateudin a CSTR. Both heat and mass balance expressionsudhave been described. Conversion, Mn and Mw were monitored.udTo test the model a reactor was designed and constructed.udA detailed description of the reactor and the experimentaludconditions used for the validation of the model are given.udThe results of these studies are presented and excellent agreementudis shown between model predictions and experiments up to 30%udconversion for Mnudw and % conversion.udA similar study is described for the anionic polymerisationudof styrene in tetrahydrofuran as solvent, in a CSTR. In thisudwork the computer model becomes 'stiff' when realistic rateudconstants are introduced in the kinetic expressions.udExperimental difficulties were encountered in obtainingudreproducible results in the anionic work. A new approach ofudusing 'scavengers' as protecting agents for the living chainsudis described. A scavenger was successfully employed in theudpreparation of block copolymers using a tubular reactor.udBlock copolymerisation, in addition to providing a means ofudchecking the number of the 'living' chains inside the reactor,udis of interest in its own right.udAll the experimental findings are discussed in relationudto the currently accepted views found in the scientificudliterature.