Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 12, 2007
Publication Date: November 5, 2007
Citation: Mohamed, A., Gordon, S.H., Biresaw, G. 2007. Poly (lactic acid)/polystyrene bioblends characterized by thermogravimetric analysis, differential scanning calorimetry and photoacoustic infrared spectroscopy. Journal of Applied Polymer Science. 106(3):1689-1696. Interpretive Summary: Blends of biodegradable polymers with synthetic polymers, called bioblends, are of interest in the development of a variety of products for use in packaging materials, medical devices, drug delivery systems, etc. Development of useful polymer bioblends is possible only when the biodegradable polymers are compatible with the synthetic polymers. Compatibility can be assessed by measuring the intermolecular interactions between the different polymers in the bioblend. In this work, the interaction in polymer bioblends containing a natural biodegradable polymer, polylactic acid, and synthetic polystyrene was investigated using thermogravimetric analysis, differential scanning calorimetry and Fourier transform infrared photoacoustic spectoscopy. The thermogravimetric and calorimetric studies indicated that blending polylactic acid with polystyrene gave bioblends that showed varying degrees of compatibility. The infrared studies revealed the presence of weak intermolecular interactions between polylactic acid and polystyrene polymers in the bioblends, which suggests development of useful bioblends from these polymers is possible.
Technical Abstract: Bioblends are composites of at least one biodegradable polymer with non-biodegradable polymer. Successful development of bioblends requires that the biodegradable polymers be compatible with other component polymers. Compatibility can be assessed by evaluating the intermolecular interactions between the component polymers. In this work, the interaction in binary bioblends comprising biodegradable poly-lactic acid (PLA) and polystyrene (PS) was investigated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). The TGA studies indicated that incorporation of PLA in PS resulted in thermal destabilization of PS. The DSC studies showed that some parameters favored partial miscibility of PS in PLA, while others favored immiscibility, such as the existence of two glass transitions. The FTIR-PAS spectra revealed the presence of intermolecular n-Pi interactions between PLA and PS and indicated the degree of interaction was dependent on the concentrations of the polymers in the bioblends. FTIR-PAS results computed via differential spectral deconvolution were consistent with, and therefore support, the results of TGA and DSC analyses of PLA/PS bioblends. The degradation kinetics, used to determine degradation mechanism, revealed two or three steps mechanism.