Oxygen sorption and transport in amorphous poly(ethylene furanoate) Steven K. Burgess a , Oguz Karvan a , J.R. Johnson a , Robert M. Kriegel b , William J. Koros a, * a School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA b The Coca-Cola Company, Atlanta, GA 30313, USA article info Article history: Received 28 May 2014 Received in revised form 15 July 2014 Accepted 24 July 2014 Available online xxx Keywords: Barriers Transport Poly(ethylene furanoate) abstract Oxygen transport in amorphous poly(ethylene furanoate) (PEF) was studied at various temperatures using complementary permeation and pressure-decay sorption techniques. A significant reduction in oxygen permeability of ~11 was observed at 35  C for PEF compared to poly(ethylene tere- phthalate) (PET), and is attributed primarily to reduction in chain segment mobility for PEF resulting from a hindrance of furan ring flipping. A custom-built high accuracy sorption system allowed determination of temperature-dependent so-called dual-mode parameters that have not been re- ported for oxygen in any polyester. Energetic parameters, i.e. the enthalpy of sorption and activation energies of diffusion and permeation, were measured for oxygen in PEF and discussed in the context of PET and related polyesters. The current work presents the first detailed study of penetrant transport in PEF, which demonstrates the impressive performance enhancements of PEF compared to PET. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Many attempts have been made to improve the barrier prop- erties of poly(ethylene terephthalate) (PET), which has an unde- sirably high oxygen permeability that hinders juice and vitamin water packaging [1]. Barrier-improvement techniques are diverse and include organic barrier coatings, multi-layered barrier poly- mers, nanocomposite materials, polymer blends, and vacuum deposited coatings [2]. While the barrier properties of PET can be improved by such techniques, complex processing steps coupled with high capital investment can hinder production on a large scale [1]. As a result, much work has also focused on the development of novel pure-polymer replacements for PET with the goal of providing enhanced performance. Poly(ethylene furanoate) (PEF) is the recently developed high- barrier polyester synthesized from ethylene glycol and 2,5- furandicarboxylic acid (FDCA). Due to the production of FDCA from renewable sugars [3], PEF also offers a bio-sourced replace- ment to poly(ethylene terephthalate) (PET) in addition to offering improved mechanical, thermal, and barrier properties [4]. Large- scale production of bio-sourced PEF can significantly reduce greenhouse gas emissions and non-renewable energy usage compared to petroleum-sourced PET [5]. Multiple studies have focused on small-scale synthesis and subsequent property char- acterization of PEF and related furan-derived polyesters [6e13]; however, only two brief reports exists regarding the barrier efficacy to oxygen [4,14]. The current work can be motivated by an abbreviated table which compares the oxygen permeability properties in amorphous PET, which is the base case for comparison, to PEF and other anal- ogously rigid polymers to PEF such as poly(ethylene naphthalate) (PEN) and poly(ethylene isophthalate) (PEI). A useful metric to normalize and compare permeability results from different studies is the so-called Barrier Improvement Factor (BIF), which can be defined as the permeability of oxygen in PET divided by the permeability of oxygen in either PEF, PEI, or PEN (BIF ¼ P PET /P PEF,- PEN,PEI ) [15]. Consequently, BIF's greater than unity illustrate barrier improvement compared to amorphous PET. Table 1 provides such permeability data and BIF comparisons between PET and related polyesters. From Table 1, it is apparent that PEF exhibits largely improved oxygen barrier properties compared to PET as evidenced by the large BIF of 11, while PEN exhibits a smaller BIF of 2.9 and PEI a BIF of 3.6. Although significantly lower than PET, the oxygen perme- ability for amorphous PEF is still higher than for semicrystalline barrier polymers such as dry Nylon-MXD6 (0.002 Barrer at 35  C [18]) and dry ethylene vinyl alcohol (EVOH, 0.0003 Barrer at 35  C * Corresponding author. Tel.: þ1 404 385 2845; fax: þ1 404 385 2683. E-mail addresses: sburgess3@gatech.edu (S.K. Burgess), bill.koros@chbe.gatech. edu (W.J. Koros). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer http://dx.doi.org/10.1016/j.polymer.2014.07.041 0032-3861/© 2014 Elsevier Ltd. All rights reserved. Polymer xxx (2014) 1e9 Please cite this article inpress as: Burgess SK, et al., Oxygen sorption and transport in amorphous poly(ethylene furanoate), Polymer (2014), http://dx.doi.org/10.1016/j.polymer.2014.07.041