Thesis
The use of a dual microbalance-calorimeter apparatus in the characterization of water sorption in polylactide-derived materials
Master of Science (M.S.), Drexel University
Feb 2011
DOI:
https://doi.org/10.17918/00008814
Abstract
This thesis demonstrates the use of the quartz crystal microbalance/heat conduction calorimeter (QCM/HCC) in obtaining data that sheds light on the sorption of water into polymer films. Subsequently, it describes the application of this device towards the investigation of the effects of chemical and physical modifications on the sorption properties of polylactide, a biobased polymer. This project is par of an overall research program seeking to improve the moisture barrier properties of polylactide while maintaining its desirable properties of biodegradability and being predominantly derived from renewable feedstocks. The Quartz Crystal Microbalance/Heat Conduction Calorimeter (QCM/HCC) is a new instrument that is capable of concurrently measuring very small changes in mass and releases of heat. Moisture sorption into a material results in changes in its microscopic conformation that can be quantified through the measurement of the heat released or absorbed over the term of the process. The QCM/HCC is capable of obtaining these two measurements and correlating them to external vapor activity in order to produce sorption isotherms and thermodynamic data. There has recently been increased interest in bio-based polymers as a replacement for a portion of the petroleum-based polymers that are commonly used in present-day society. The utility of such polymers has been hindered by their tendency to take up water, which precludes their extended use. It is desirable to develop polymers produced primarily from biological feedstocks that retain their biodegradability while exhibiting improved moisture barer properties. This thesis presents an experimental set-up centered around the QCM/HCC that demonstrates the effectiveness of the device in efficiently obtaining mass uptake and heat evolution data that quantify the effects of water sorption on a polymer film. It then provides data on the effects of the addition of hydrophobic additives to polylactide through both copolymerization and physical blending. Sorption data on PLA films demonstrate an increasing enthalpy of sorption that gradually approaches the value of the enthalpy of vaporization of water, indicating the clustering of water molecules within this polymer, in contrast to similar data on films of the more hydrophilic PHEMA, where the enthalpy of sorption is significantly lower. Although blending polylactide with poly(dihexadecylglycolide) results in a decreased solubility, the amount of the more hydrophobic component that must be added to produce a significant change is prohibitive. Copolymerization with poly(dihexadecylglycolide) appears to be a more promising technique for changing the moisture barer properties of polylactide.
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Details
- Title
- The use of a dual microbalance-calorimeter apparatus in the characterization of water sorption in polylactide-derived materials
- Creators
- Joshua Adam Meisner
- Contributors
- Richard Allan Cairncross (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xiv, 108 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- Chemical (and Biological) Engineering (1970-2026); College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021888816404721