Influence of the transesterification catalyst structure on the reactive compatibilization and properties of poly(ethylene terephthalate) (PET)/dibutyl succinate functionalized poly(ethylene) blends

The transesterification between poly(ethylene terephthalate) (PET) and dibutyl succinate functionalized polyethylene (POF) was studied by preparing blends in a discontinuous mixer in the presence of different Zn and Ti catalysts. In particular the catalytic activities of Zn(OOCCH₃)₂, Ti(OBu)₄, ZnO and TiO(OCCH₃)₂ were compared. The mechanism of reactions occurring in the melt was studied both by a model compounds approach and by characterizing the macromolecular products of the melt processing by means of selective extractions, infrared analysis and the determinations of the molecular weight of PET. The results are discussed in terms of electrophilicity and nucleophilicity of the different catalysts. The catalysts structure also affected the phase distribution. In fact from a morphologic point of view in PET matrix blends the use of zinc derivatives yielded preferentially dispersed-like phase distribution, while the use of titanium derivatives resulted in partially co-continuous phase morphology. The stability of the attained phase distribution was also monitored during compression moulding and it evolved rapidly in fully dispersed phase morphology. The tensile properties of compression moulded films revealed that the occurred reactions and morphological assessment induced a general decrease of tensile modulus and an increase of elongation at break.