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Melting point depression in biodegradable polyesters

Murphy, Shona (2011)
M.Res. thesis, University of Birmingham.

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Investigation into the crystallisation kinetics and melting point depression of poly(L-lactideco-meso-lactide) with approximately 3.3% D-lactide content (PLA 3051D) was undertaken. The rate of crystallisation was too slow for a crystallisation exotherm to be detected by the DSC, therefore hot-stage microscopy was used as an alternative method to characterise the crystallisation behaviour. Light intensity with time during isothermal crystallisation of a thin polymer film (<15μm) was measured. The results were normalised in order to calculate crystallisation half-life (t0.5). From half-life calculations, the optimal crystallisation temperature was found to be 118°C. By replacing the light dependant resistor with a digital camera, the diameter growths of individual spherulites could be measured minute-by-minute. Using the results obtained through hot-stage microscopy, re-processing of PLA could be carried out to restore the original crystallinity at Tmax 118°C. Plots showing % crystallinity with storage time at 118°C indicated a storage time of 2 hours was required to restore the crystallinity to 40%. Studies using the high pressure DSC found that with increasing CO2 pressure up to 60 bar, the melting point decreased from 152 to 142°C . An alternative biodegradable polymer, polycaprolactone CAPA 6800 was investigated with high pressure DSC as a comparison polymer to polylactic acid. Similarly to PLA, the melting point of PCL showed a significant reduction (55 to 40°C) when soaked with increasing pressures of CO2.

Type of Work:M.Res. thesis.
Supervisor(s):Jenkins, Mike and Leeke, Gary
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Engineering, Department of Metallurgy and Materials
Subjects:TN Mining engineering. Metallurgy
TA Engineering (General). Civil engineering (General)
Institution:University of Birmingham
ID Code:1611
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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