{"id":{"repo_id":"birmingham","oai_identifier":"oai:etheses.bham.ac.uk:1611"},"canonical_url":"https://search.dev.ndltd.org/etd/birmingham/oai:etheses.bham.ac.uk:1611","repository":{"repo_id":"birmingham","name":"University of Birmingham","base_url":"https://etheses.bham.ac.uk/cgi/oai2"},"display":{"title":"Melting point depression in biodegradable polyesters","abstract":"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.","abstract_html":"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 (&lt;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.","abstract_has_math":false,"creators":["Murphy, Shona"],"institution":"University of Birmingham","degree_name":"m_rs","degree_level":"m_rs","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-07","date_published":"2011-07","updated_at":"2026-07-24T01:11:37Z","subjects":["TN Mining engineering. Metallurgy","TA Engineering (General). 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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."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Melting point depression in biodegradable polyesters"]}]}],"canonical_facts":{"dc:contributor.sponsor":["na"],"dc:creator":["Murphy, Shona"],"dc:date":["2011-07"],"dc:date.issued":["2011-07"],"dc:description.abstract":["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. 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