Contributions of intramolecular and intermolecular energy changes to strain-induced enthalpy relaxation in uniaxially drawn poly(lactic acid) films. (1st May 2015)

• Record Type: Journal Article
• Authors: Kim, Min Sung; Chang, Jin-Hae; Lee, Sang Cheol
• Is Part Of: Polymer. Volume 64(2015)
• Page Start: 176
• Page End: 182
• Publication Date: 2015-05-01
• Subjects: Poly(lactic acid) -- Endotherm -- Strain-induced enthalpy relaxation; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2015.03.048
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Blends of poly(lactic acid)s (PLAs) containing three different concentrations of d -isomer (i.e., 1, 4, and 10 mol%; referred to as PLA1, PLA4, and PLA10, respectively) with poly(dl -lactic acid) (PDLLA) were prepared via solution blending. The three PLAs were miscible with PDLLA, as determined by dynamic mechanical analysis. Drawn films of PLA1/PDLLA, PLA4/PDLLA, and PLA10/PDLLA blends exhibited endothermic peaks just above the glass transition temperature, which is evidence of strain-induced enthalpy relaxation. A thermodynamic model for the miscible blend system was applied to determine contributions of intramolecular and intermolecular energy changes to strain-induced enthalpy relaxation for PLA1, PLA4, and PLA10; the resultant values suggested that intramolecular energy changes are mainly responsible for strain-induced enthalpy relaxation. Graphical abstract: Highlights: Drawn films of PLA blends exhibit endothermic peaks just above glass transition temperature. For PLA containing less than 4 mol% of d -isomer, almost 60% of the endothermic heat originates from intramolecular energy change. As the d -isomer content of PLA increases, the contribution of intramolecular energy change to the endothermic heat increases. Overall, intramolecular energy change is primarily responsible for strain-induced enthalpy relaxation.