Journal of Thermal Analysis and Calorimetry, Vol. 78 (2004) 865–884 THE EFFECT OF CHAIN EXTENSION ON THE THERMAL BEHAVIOUR AND CRYSTALLINITY OF REACTIVE EXTRUDED RECYCLED PET F. Awaja 1 , F. Daver 1* , E. Kosior 2 and F. Cser 3 1 School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, PO Box 71, Bundoora, Victoria 3083, Australia 2 Visy Technical Centre, 23 Ash Road, Prestons, NSW 2170, Australia 3 Rheology and Materials Processing Centre, RMIT University, GPO Box 2476V, Melbourne, Victoria 3001, Australia Abstract Recycled poly(ethylene terephthalate) (R-PET) was chain extended with pyromellitic dianhydride (PMDA) in a commercial size twin-screw reactive extrusion system. Temperature-modulated differ- ential scanning calorimetry (TMDSC) was used to evaluate the effect of the chain extension process on the thermal transitions and crystallinity of R-PET. Reactive extruded recycled PET (RER-PET) samples were tested based on different PMDA concentration and reactive extrusion residence times. The glass transition temperature (T g ) did not show a significant change as a function of PMDA addi- tion or the extrusion residence time. Melting temperature (T m ) and crystallisation temperature (T c ) decreased with increasing PMDA concentration and with increasing extrusion residence time. RER-PET samples showed double melting peaks, it is believed that different melting mechanism is the reason behind this phenomenon. The crystallinity of RER-PET samples is lower than that of R-PET. RER-PET samples at constant PMDA concentration showed a decrease in crystallinity with increasing extrusion residence time. Results suggest that the reactive extrusion process is more de- pendent on PMDA concentration rather than reactive extrusion process residence time. Keywords: chain extension, crystallinity, reactive extrusion, recycled PET, TMDSC Introduction Poly(ethylene terephthalate) (PET) is a widely used thermoplastic polyester in manu- facturing of textile fibers, soft-drink bottles, photographic films, audio/video tapes and packaging films. Owing to the increased awareness of environmental issues, recycling of PET has recently attracted great interest around the world. However, the use of recy- cled PET (R-PET) in many value-added applications is limited due to lack of desirable mechanical properties and high melt strength, which depend on the molecular charac- teristics, such as average molecular mass, molecular mass distribution and chain branching. During the melt processing of R-PET at high temperatures, R-PET under- 1388–6150/2004/ $ 20.00 © 2004 Akadémiai Kiadó, Budapest Akadémiai Kiadó, Budapest Kluwer Academic Publishers, Dordrecht * Author for correspondence: E-mail: daver@rmit.edu.au