DSC study of biodegradable poly(lactic acid) and poly(hydroxy ester ether) blends

• Published in: Thermochimica acta Vol. 406; no. 1; pp. 115 - 127
• Main Authors: Cao, X, Mohamed, A, Gordon, S.H, Willett, J.L, Sessa, D.J
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 28-11-2003; Elsevier Science
• Subjects: Applied sciences; Blends; Exact sciences and technology; Miscibility; Organic polymers; PHEE; Physicochemistry of polymers; PLA; Properties and characterization; Thermal and thermodynamic properties; Thermal properties; Thermal properties; Miscibility; Blends; PLA; PHEE; Differential scanning calorimetry; Mixing; Melting; Polymer blends; Cooling; Molten state; Ether copolymer; Glass transition temperature; Alcohol copolymer; Melt crystallization; Ester copolymer; Lactic acid polymer; Heating; Thermal analysis
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/S0040-6031(03)00252-1

DSC heating–cooling cycles (0–200
°C) were repeated on poly(lactic acid)/poly(hydroxy ester ether) (PLA/PHEE) blends to study the miscibility of the two polymers. Initial thermograms show two distinguishable
T
g values corresponding to the respective neat polymers, accompanied by a crystallization and a melting peak for the PLA. Subsequent DSC runs show that the thermogram profiles depend on the number of heating–cooling cycles the blends are subjected to. As the number of cycles increases,
T
g,PLA and
T
g,PHEE shift toward each other and eventually merge into a single
T
g, while Δ
H
c and Δ
H
m of PLA increase to maximum values then decrease to zero. It is concluded that after repeated heating–cooling cycles, PLA and PHEE achieve mixing on a molecular level, i.e. PLA and PHEE are miscible. The number of cycles needed to reach a single
T
g, maximum Δ
H and zero Δ
H, are dependent on blend composition.