# Synergistic Modification of Recycled PET Using Halloysite Nanotubes and a Reactive Terpolymer for Enhanced Toughness and Processability

## TL;DR

This study improves the toughness and processability of recycled PET by combining halloysite nanotubes and a reactive terpolymer, enabling its use in higher-value applications.

## Contribution

The novel synergistic modification using HNTs and E-MA-GMA enhances recycled PET properties beyond individual additives.

## Key findings

- The combined use of HNTs and E-MA-GMA significantly restricts PET molecular chain relaxation.
- Recycled PET composites with HNTs and E-MA-GMA show 2.28 times higher impact strength under high-mold-temperature injection molding.
- The synergistic modification reduces crystallinity, improving impact resistance after high-temperature treatments.

## Abstract

Polyethylene terephthalate (PET) has become the predominant material for single-use packaging owing to its cost and performance advantages. However, massive post-consumer waste leads to environmental concerns, and recycled PET from thermomechanical processing followed by chain extension often suffers from low toughness and poor processability, restricting its use to low-value applications. In this study, halloysite nanotubes (HNTs) and ethylene–methyl acrylate–glycidyl methacrylate random terpolymer (E-MA-GMA) were melt-blended with recycled PET to examine their synergistic modification effects. The DSC results show that HNTs retain a nucleating effect on recycled PET even with the co-addition of E-MA-GMA, albeit with a substantial reduction compared with their effect when used alone. Nevertheless, rheological measurements indicate that the combined introduction of E-MA-GMA and HNTs imposes a significantly stronger restriction on the relaxation behavior of recycled PET molecular chains than the individual addition of either HNTs or E-MA-GMA. This is attributed to the interfacial reactions between E-MA-GMA and the recycled PET matrix, as well as between E-MA-GMA and HNTs, leading to the formation of branching and hybrid structures. This synergistic restraint markedly reduces the crystallization growth rate of PET. As a result, the recycled PET/E-MA-GMA/HNTs composites maintain relatively lower crystallinity compared with the recycled PET/E-MA-GMA composite after high-temperature injection molding or annealing treatment, leading to superior impact resistance. The impact strength of the recycled PET/E-MA-GMA/HNTs composites is 2.28 and 2.14 times that of the recycled PET/E-MA-GMA composite under high-mold-temperature injection molding and annealing conditions, respectively. The approach presented here facilitates the substitution of virgin plastics with recycled PET in demanding applications.