Abstract
It is well established that the application of ultrasound to a polymeric system causes degradation by preferential cleavage of the longer chains at or near the centre of the chain. This study aims to apply this to an existing industrial process where polymeric chains (dextran) are degraded via acid hydrolysis and fractionation.The effect of parameters such as ultrasonic power, reaction temperature and
solution concentration upon established and novel methods of kinetic analysis are discussed for partially fractionated dextran (that is a semi industrial sample). It is shown that the degradation rate increases with increasing ultraonic power and decreases with reaction temperature. This latter is the reverse of expected Arrhenius behaviour.
A model is presented whereby either the molar mass of a solution after a period of sonication or the sonication period necessary to acieve a certain molar mass can be predicted. A computer program has subsequently been generated to facilitate computer control of the industrial process.
The model has been successfully transferred to a system using dextran that has undergone no prior fractionation (that is an industrial sample). It is shown that the replacement of the conventional acid hydrolysis procedure with ultrasonic hydrolysis enhances the rate constant by a factor of twenty whilst eliminating the need for subsequent fractionation. The model was subsequently applied to a large scale ultrasonic reactor which showed agreement for short reaction times.
| Date of Award | 1997 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Timothy Mason (Supervisor) & John P Lorimer (Supervisor) |