ORIGINAL PAPER Non-isothermal crystallization kinetics and nucleation activity of hyperbranched polyester (HBPET) in recycled PET Haroon A. M. Saeed • Yassir A. Eltahir • Yumin Xia • Wang Yimin Received: 18 July 2013 / Revised: 16 September 2013 / Accepted: 7 November 2013 / Published online: 20 November 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract The non-isothermal crystallization of pure recycled polyethylene tere- phthalate (RPET) and its blends with 3 and 5 wt% hyperbranched polyester (HBPET) were investigated by differential scanning calorimetry (DSC). The DSC curves demonstrate that the melt-crystallization temperatures of the blends are always higher than that of pure RPET regardless of the cooling rate. Their non- isothermal crystallization kinetics was further analyzed with modified Avrami equation, Ozawa equation and Mo method. The analysis reveals that the crystalli- zation half-time (t 1/2 ) of the blends is shorter than pure RPET. The activation energy of crystallization of RPET was also determined according to Kissinger method and it is found to decrease remarkably in RPET-3 and RPET-5 blends. All the results indicate that HBPET serves as an effective nucleating agent for RPET. Keywords Recycled PET  Non-isothermal crystallization  Crystallization half-time (t 1/2 )  Hyperbranched polyester  Nucleating activity Introduction Hyperbranched polymers (HBPs) have received extensive attention during the past decades due to their unique features when compared with their linear analogs, such as 3D architecture, good solubility, and low melting viscosity, especially the presence of large numbers of functional end groups [1–5]. Unlike dendrimers, the hyperbranched polymers can be synthesized via one step reaction; therefore, they represent economically promising products for large-scale industrial applications, H. A. M. Saeed  Y. A. Eltahir  Y. Xia  W. Yimin (&) College of Materials Science and Engineering, State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, 2999 North Renmin Road, Shanghai 201620, People’s Republic of China e-mail: ymw@dhu.edu.cn 123 Polym. Bull. (2014) 71:595–612 DOI 10.1007/s00289-013-1080-3