On the compatibilization of PET/HDPE blends through a new class of copolyesters T.L. Dimitrova a, * , F.P. La Mantia a , F. Pilati b , M. Toselli c , A. Valenza d , A. Visco d a Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, Universita ` di Palermo, Viale delle Scienze, 90128 Palermo, Italy b Dipartimento di Chimica, Universita ` di Modena, Via G. Campi 183, 41100 Modena, Italy c Dipartimento di Chimica Applicata e Scienza dei Materiali, Universita ` di Bologna, Viale Risorgimento 2, 40136 Bologna, Italy d Dipartimento di Chimica Industriale e Ingegneria Chimica, Universita ` di Messina, Salita Sperone 31, 98166 S. Agata Messina, Italy Received 16 April 1999; received in revised form 10 September 1999; accepted 24 September 1999 Abstract Polyethyleneterephthalate (PET) and polyethylene are incompatible polymers and their blends show, in general, poor properties. Compa- tibilization is then a necessary step to obtain blends with good mechanical and barrier properties. In this work different compatibilizing agents were used, i.e. a maleic anhydride elastomer and some new products containing graft-copolymers having polyester segments grafted onto polyethylene backbone chains. Both the functionalized elastomer and the new products drastically improve the morphology and the ductility of the blend. In the case of the modified elastomer the compatibilizing action has been attributed to the formation of H-bonds whereas the copolymers contained in the new products act as compatibilizing agents as they contain polyester segments and polyethylene segments with thermodynamic affinity with PET and polyethylene, respectively.  2000 Elsevier Science Ltd. All rights reserved. Keywords: PET/HDPE blends; Copolyesters; Compatibilization 1. Introduction Polyethyleneterephthalate (PET) is widely used for packaging—mostly bottles—electronics and other applica- tions. The blends of PET with other polymers, and in parti- cular with polyolefins, may offer an attractive balance of mechanical and barrier properties and of processability. Moreover, these polymers are found easily in the post- consumer urban plastic waste. The possibility of recycling these mixtures without any previous separation of the components could be a good chance for the economic of the recycling. The incompatibility of these two classes of polymers, polyesters and polyolefins, gives rise to a “bad” morphology—gross phase separation, lack of adhesion between the phases—and then to poor mechanical and barrier properties. Compatibilization is then a necessary step to obtain blends of PET and polyolefins with good properties both from virgin and recycled materials. On the basis of its structure, PET is capable both of chemical reactions with polar polymers and of specific polar interactions, like H-bonding. Some attempts have been done to form compatible blends of PET with non- polar polymers by using elastomers [1], EVA [2], EAA and EMA [3], or a functionalized third component, in parti- cular PP-g-MA [4], PE-g-MA [5,6], PE-g-AA [7], SEBS-g- MA [8,9] and vinyl acetate (EVA) based graft-copolymers [8,10] and organo-titanate coated CaO [8]. Both improved morphology and better mechanical properties have been observed by using some of these components. In this work uncompatibilized blends of PET and high- density polyethylene (HDPE) have been prepared and their morphology, rheological and mechanical properties have been compared with those of the same blends compatibi- lized with new ad hoc synthesized EVA and EVOH based copolyesters. Blends compatibilized with commercial maleic anhydride functionalized elastomers have been prepared for comparison. All the compatibilized blends have shown a dramatic change of the morphology, an enhancement of the viscosity and a significant improvement of the mechanical properties with respect to the uncompa- tibilized binary blend. 2. Experimental 2.1. Materials and blends preparation The materials used in this work were PET, h Polymer 41 (2000) 4817–4824 0032-3861/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S0032-3861(99)00709-0 * Corresponding author.