Carbon dioxide assisted blending of biodegradable polyesters

Murphy, Shona Hollie (2015). Carbon dioxide assisted blending of biodegradable polyesters. University of Birmingham. Ph.D.

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Abstract

Blends of biodegradable polyesters; poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) were produced by a variety of preparation methods; solution casting, melt blending and blending in the presence of carbon dioxide using a single screw extruder. The blends were characterised using scanning electron microscopy (SEM), mechanical testing, differential scanning calorimetry (DSC), Fourier Transform infrared spectroscopy (FTIR), rheology and size exclusion chromatography (SEC). Comparison of the blends produced via the different preparation techniques indicated that carbon dioxide was able to improve the morphology and mechanical properties of the PLA/PCL blends.

The influence of carbon dioxide on the reptation time of poly(ε-caprolactone) was investigated using oscillatory rheology. It was shown that by introducing CO2 into the polymer melt, the reptation time was significantly reduced, providing evidence that CO2 was interacting with this polymer. Further analysis of the data showed that the activation energy to flow was reduced, which was consistent with the reduction in the reptation times.

Flash DSC, a relatively new thermal analysis technique, was used to explore areas of polymer science that are otherwise unachievable using conventional DSC. It showed the ability to prevent reorganisation and crystallisation in partially crystalline polymers such as poly(ε-caprolactone) and was able to evaluate the activation energy of the glass transition temperature for different amorphous and partially crystalline grades of PLA.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):