Contribution of compatibilizer backbone to degradation and retained functionality of multiple extruded polypropylene/poly(ethylene terephthalate) blends

Abstract

This study assesses thermal and morphological stabilization of three compatibilizers during mechanical recycling of polymer blends. Polypropylene/poly(ethylene terephthalate) blends compatibilized with three different maleic anhydride grafted compatibilizers were extruded five times via single‐screw extrusion. The backbones of the compatibilizers are (1) polypropylene‐based, (2) an elastomer block copolymer poly(styrene‐co‐[ethylene‐butylene]‐styrene), and (3) a polyolefin elastomer. The degradation and retained functionality of these compatibilizers was assessed by means of simultaneous thermo‐gravimetric analysis, melt flow index, a morphology study, differential scanning calorimetry and tensile testing. The results show that degradation of the compatibilized blends during multiple processing is low, although the core stability of the blends depends on the initial stability of all of the components in the blend. The thermal stability across the five extrusions was the most favorable for the matrix based grafted compatibilized blend. The functionality of the compatibilizers did show minor morphological destabilization but did not affect the mechanical properties.

Onset critical strains as an effective parameter for compatibilizer efficiency in a polypropylene‐poly(ethylene terephthalate) blend

“…In this case it suggest that the amorphous mobility of the PPgMAH blend is the lowest. This correlates with the DSC results from previous research 18 wherein the crystallinity was slightly higher due to the PP, which has a stiffer backbone than the elastomeric compatibilizers backbone and can co‐crystallize with the matrix if the chain lengths are sufficiently long. The binary blend has a slightly lower plateau height than PP‐PET‐PPgMAH.…”

“…However, at the onset strains of the elastic plateau ( ε C ), it is expected that the deformed crystals under uniaxial stretching in the bulk of all phases have started to fibrillate and consequently become less dependent of the original morphology. This is valid if the dispersion of the blends was fine enough at the beginning, as shown in Reference 18.…”

“…Accordingly, the onset of collective inter‐ and intra‐lamellar slip occurs later for the ternary blends compared to the binary blend. The results of the tensile test were presented and discussed in previous research 18,19 and showed the highest strain at zero slope for the first extrusion for PP‐PET‐SEBSgMAH followed in decreasing order by PP‐PET‐POEgMAH, PP, PP‐PET‐PPgMAH, PP‐PET, and the lowest strain at yield for PET.…”

“…The onset of coarse slip ( ε B ) is defined by the ultimate tensile strength (based on the maximum engineering tensile stress) before the onset of necking. The strains at yield zero slope of all materials, measured at the ultimate tensile strength, is presented in Table 2 and shows major differences suggesting a stronger interaction between the polymers in the ternary blends 18 and consequently a better stress dissipation in the samples. Accordingly, the onset of collective inter‐ and intra‐lamellar slip occurs later for the ternary blends compared to the binary blend.…”

“…These tests were performed on the matrix polymer PP, its binary blend with PET and three compatibilized ternary blends of PP‐PET with, PP grafted with maleic anhydride (PPgMAH), poly(styrene‐(ethylene‐co‐butylene)‐styrene) block copolymer grafted with maleic anhydride (SEBSgMAH) or polyolefin elastomer grafted with maleic anhydride (POEgMAH). The selected blends have been discussed in our previous works on the long‐term mechanical, morphological and thermal‐mechanical stability of multiple processed compatibilized PP‐PET blends 18,19 …”