Reactive‐extrusion route for the closed‐loop recycling of poly(ethylene terephthalate)

Abstract

The effectiveness of the reactive extrusion technique was investigated for poly(ethylene terephthalate) to promote the concept of closed-loop recycling, that is, the reuse of waste material in the initial application. More specifically, a chain-extender system, consisting of pyromellitic dianhydride, polyol, and a catalyst, was employed, and its efficiency regarding the improvement of the recyclate quality was evaluated. Accordingly, rheological and thermal characterizations were performed and used as criteria of the modification induced in the polymer molecular structure during processing due to the counteracting degradation and chainextension reactions. In particular, the molecular weight, related to intrinsic viscosity and melt flow rate measurements, of modified poly(ethylene terephthalate) samples was found to increase with the additive content. Simultaneously, a decrease in the crystallinity was observed, attributed to the branching effect of the chain extender, which restricted the ability of the macromolecules to organize in the crystal structure. Beyond a critical concentration of the additive system, the molecular weight of the treated samples started to decrease again, and this was accompanied by a small increase in the crystallinity.

Poly (ethylene terephthalate) thermo-mechanical and thermo-oxidative degradation mechanisms

“…From this scan, the melting temperature (T m ) and enthalpy of fusion (DH m ) were calculated. The degree of crystallinity was calculated from Equation (1), where DH c is the enthalpy of crystallization and DH o is the enthalpy of crystallization of PET with 100% crystallinity, 120 J g À1 [23,24]. …”

Influence of accelerated aging on clay-reinforced polyamide 6

“…Consequently, their physical and mechanical properties are negatively affected in a way which is generally to the detriment of serviceableness. The extent of thermo-oxidative degradation depends mostly on the polymer structure and processing history, the presence of additives, as well as the environment of the targeted application [19][20][21].…”

Degradation of poly(ethylene terephthalate)/clay nanocomposites during melt extrusion: Effect of clay catalysis and chain extension

“…To compensate for polymer degradation, the use of chain extenders had been proposed in many studies as an effective method of increasing molecular weight [24][25][26][27][28][29][30]. As a common chain extender among the reported extenders, pyromellitic dianhydride (PMDA) increased the intrinsic viscosity and molecular weight of PET significantly with very low loading.…”