Structural stabilizing effect of SEBSgMAH on a PP-PET blend for multiple mechanical recycling

The stabilising effect of a compatibiliser for long term mechanical recycling of polymer blends is assessed. A polypropylene (PP)/poly(ethylene terephthalate) (PET) blend and their mono-materials were multiple extruded (5 times). A fourth set was made with the addition of a compatibiliser block copolymer poly(styrene-co-(ethylene-butylene)- styrene) grafted with maleic anhydride (SEBSgMAH) in order to evaluate the (lack of) progressive degradation effects and the morphology stabilisation of adding the compatibiliser. After the third reprocessing cycle Scanning Electron Microscopy (SEM) showed a severe destabilisation of the PP-PET blends while there was only minor destabilisation observed for the cornpatibilized mix. Differential Scanning Calorimetry (DSC) highlighted an increase in PETs crystallinity enthalpy for every set. This increase was less prominent for the compatibilised blend because fractionated crystallisation occurred. Fourier Transformed Infrared (FTIR) and rotational rheology confirmed that the degradation was less severe for the compatibilised blend. The demixing and degradation resulted in changed mechanical properties shown by a decreased strain at break and strain at yield. This decrease was more pronounced in the uncompatibilised blend than in the compatibilised blend over the five extrusions, thus confirming the stabilisation of the ternary blend. (C) 2019 Elsevier Ltd. All rights reserved.