Thermochimica Acta 406 (2003) 115–127 DSC study of biodegradable poly(lactic acid) and poly(hydroxy ester ether) blends  X. Cao a , A. Mohamed b , S.H. Gordon c , J.L. Willett c,∗ , D.J. Sessa c a Department of Chemistry, Bradley University, 1815 N. University Street, Peoria, IL 61614, USA b Cereal Products and Food Science Research Unit, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61614, USA c Plant Polymer Research Unit, National Center for Agriculture Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61614, USA Received 5 November 2001; received in revised form 8 April 2003; accepted 8 April 2003 Abstract 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 H c and 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 H and zero H, are dependent on blend composition. Published by Elsevier B.V. Keywords: PLA; PHEE; Blends; Miscibility; Thermal properties 1. Introduction The use of non-renewable, petroleum-based chem- icals for the synthesis and manufacture of commodity polymers, and the environmental concerns generated by their disposal, pose major challenges to the poly- mer industry. The main strategies to address these problems are to utilize polymeric materials from  Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable. ∗ Corresponding author. Tel.: +1-309-681-6556; fax: +1-309-681-6691. E-mail address: willetjl@ncaur.usda.gov (J.L. Willett). renewable sources, and to develop biodegradable polymeric materials. One of the most abundant polymeric materials from renewable resources is starch. While abundant and inexpensive, however, starch alone as a mate- rial does not offer satisfactory properties for many applications. Meanwhile, the few synthetic biodegrad- able polymers with satisfactory properties are pro- hibitively expensive when compared to commodity non-biodegradable polymers. A common approach is to make blends/composites of starch and other biodegradable synthetic polymers to produce materi- als of satisfactory properties and a low overall cost. Three-component blends of cornstarch, poly(lactic acid) (PLA), and poly(hydroxy ester ether) (PHEE), have been prepared with satisfactory properties and 0040-6031/$ – see front matter. Published by Elsevier B.V. doi:10.1016/S0040-6031(03)00252-1