Improving the flame‐retardant property of bottle‐grade PET foam made by reactive foam extrusion

Christian Bethke,Lais Weber,Daniela Goedderz,Volker Altstädt,Manfred Döring,Tobias Standau

doi:10.1002/app.49042

Abstract

AbstractUpcycling of low intrinsic viscosity (IV) poly(ethylene terephthalate) (PET) grades, such as bottle‐ or recycled grades, by a reactive foam extrusion process, provides an appropriate alternative to high pricing, high IV grades commonly used for foaming applications. However, the drawback of bottle‐grade PET foams is its flame retardant (FR) performance. In this study, pyromellitic dianhydride was used as a chain extender to foam bottle‐grade PET. The influence of different FRs, containing halogenated (HFR) and four different phosphorous‐based types, on the processability and final foam properties was investigated. HFR showed better processability to achieve proper foams with fine morphology compared to P‐based FRs, where the FR content was adjusted between 2 and 5 wt%. However, HFR exhibited lower FR performance by cone calorimeter testing compared to the P‐based FRs and the commercial reference foam Kerdyn. Nonetheless, all of the FRs can only improve the time to ignition of the neat PET foams while the other values depend on the specific type of FR. In addition, all FR foams have improved mechanical properties more than twice in comparison to the neat PET foam.

Highlights

Polymeric foams are favorable in modern engineering, as they combine lightweight, along with material saving, low thermal conductivity, and high specific mechanical performance
A bottle-grade poly(ethylene terephthalate) (PET) was successfully foamed by reactive foam extrusion, using Pyromellitic dianhydride (PMDA) as a chemical modifier, in the presence of different flame retardant (FR)
This was limiting the amount of FR in the foam samples. 3% PSMP was found to be less suitable for PET processing, as a significant chain degradation of the PET matrix and processing fluctuations could be observed

Summary

Introduction

Polymeric foams are favorable in modern engineering, as they combine lightweight, along with material saving, low thermal conductivity, and high specific mechanical performance. The influence of the different types of FRs, halogenated and P-based, on the reactive foam extrusion process of a bottle-grade PET with PMDA is studied. A low IV (and low molecular weight) bottle-grade PET is processed by reactive foam extrusion with PMDA as CE and different commercially available FR in order to investigate the influence of the FRs on the foaming process and resulting foam properties.

Results

Conclusion