Mechanical Recycling of PET Waste from Non-Woven Fabrics by Reactive Extrusion with Chain Extenders

Abstract

Mechanical recycling of poly (ethylene terephthalate) (PET) is an important industrial activity with direct effect for environmental saving. However, recycled PET (R-PET) undergoes progressive degradation during each recycling process, leading to considerable loss of properties such as mechanical, thermal and melting strength. Chain extenders have been successfully used to increase molecular weight of R-PET, improving process ability and mechanical performance of the material. The aims of this work was to evaluate the performance of the compounds polymeric methylene diphenyldiisocyanate (PMDI) and bis-(2,4-di-t-butylphenol) pentaerythritoldiphosphite (Irgafos ® 126) for potential use as chain extenders when compared to the traditional chain extender pyromelliticdianhydride (PMDA). Tensile testing, differential exploratory calorimetry, viscometry and dynamic rheometry were used to evaluate changes in mechanical properties, crystallinity, molecular weight and rheological properties of R-PET. PMDI showed effective action on increase in molecular weight and improvements in mechanical and rheological properties of R-PET, while Irgafos 126 causes depreciation of properties of the R-PET after initially to increase the molecular weight of the polymer. Thus, the use of PDMI as chain extension can represent an important alternative for mechanical recycling of highly degraded PET.

Influence of Chain Extenders on Recycled Standard and Opaque PET Rheology and Melt-Spun Filament Properties

“…They have been widely studied to improve the recycled PET properties. Di-epoxides, bis-oxazolines, and diisocyanate are commonly used for linear chain extension, and anhydride-based or epoxy-based compounds are commonly used for branched structures. , Among them, the most widely used and studied compounds for branched structures are a multifunctional epoxide oligomer named JONCRYL and a tetrafunctional modifier pyromellitic anhydride (PMDA). − The use of these additives leads to an increase in intrinsic viscosity, molar mass distribution, and long-chain branching, resulting in higher melt elasticity and shear-thinning behavior. Regarding linear chain extension, 2,2′-bis­(2-oxazoline) (BOZ) and 1,3-phenylene-bis-oxazoline (PBO) are commonly used to improve the molar mass and reduce the carboxylic content of PET. ,,− However, a decrease in the degree of crystallinity is often observed. , The use of chain extenders for fiber spinning production is scarcer in the literature, but Qu et al used PMDA to create long-chain branches in PET melt-spun filaments.…”