Enhanced PET processing with organophosphorus additive: Flame retardant products with added-value for recycling

Abstract

At elevated temperatures, polyethylene terephthalate (PET) is known to undergo a cascade of interconnected chemical reactions, in particular oxidative crosslinking, which can lead to severe limitations in processability, product properties, and recyclability. To control such undesired reactions, a newly synthesized phosphorus-based additive with promising flame retardant properties (T. Stelzig et al. Dopo-Based Hybrid Flame Retardants. EP2921498 (A1), 2015), by the chemical name 6-((1-oxido-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octan-4yl)methoxy)dibenzo[c,e][1,2]oxaphosphinine 6-oxide (DOPO-PEPA, or simply DP), was added to PET in different concentrations. To assess the miscibility of DP and PET at the nanoscale, a multiscale simulation scheme was developed by combining molecular dynamics and dissipative particle dynamics. DP showed a prominent inter-chain lubrication effect in PET in extrusion experiments. To replicate the heating cycles during repeated recycling, the thermal stability of PET melts was assessed on extended timescales using rheological measurements. Time-resolved frequency sweep experiments were conducted with or without the novel DP additive, under air and nitrogen atmospheres. By combining various chemical analysis techniques, a chemical stabilizing mechanism could be proposed that describes how the DP molecule intervenes with the-1-This document is the accepted manuscript version of the following article:

Mechanical Recycling of Packaging Plastics: A Review

“…for PET. [ 47,48,50 ] Thus, the length of polymer chain controls degradation kinetics (suggesting that it can autoaccelerate through repeated extrusion) whereas thermo‐oxidative processes are dictated by the both structure of and oxygen diffusion through the polymer matrix. [ 51 ] Environmental oxygen reacts with shear‐induced radicals and subsequent reactions produce peroxy radicals which propagate radical decomposition.…”

Tuning gradient microstructures in immiscible polymer blends by viscosity ratio

“…The design of new functional materials often requires a precise control of the structure at different scales . In polymer blends, this task is quite challenging due to the complex relationships between their properties, microstructures, and processing conditions.…”

Melt-Spun Fibers for Textile Applications

“…Dispersive additives can act as lubricants for the matrix polymer by reducing apparent viscosity, and thus temperature or pressure required for extrusion [ 125 ]. In consequence, lubricants can even render polymers melt-spinnable whose melting temperature exceeds their degradation temperature [ 126 ]. Polymer processing aids like fluoropolymers can delay the onset of flow instabilities by thinly coating the die wall, thus reducing adhesion between polymer and wall and in consequence promote slippage [ 127 , 128 ].…”