Penetrant transport in semicrystalline poly(ethylene furanoate) Steven K. Burgess a , Graham B. Wenz 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 14 February 2016 Received in revised form 10 June 2016 Accepted 17 June 2016 Available online 23 June 2016 Keywords: Barrier Transport Semicrystalline abstract This study investigates the penetrant transport properties of water, oxygen, and carbon dioxide at 35  C in poly(ethylene 2,5-furanoate) (PEF) isothermally crystallized at 115 and 160  C. Dual-mode analysis of the water sorption isotherms for the semicrystalline vs. amorphous PEF samples indicates that the Henry’s law sorption parameter (k D ) is reduced for the semicrystalline samples in direct proportion to the volume fraction crystallinity measured via both density and thermal methods. While the k D for water obeys the simple two-phase model of crystallinity, an unexpected large reduction in the Langmuir ca- pacity constant (C H 0 ) for the semicrystalline vs. amorphous samples resulted in an overall reduction in water sorption capacity greater than predicted by the two-phase model. Corroboration of this behavior for water is provided by independent oxygen and carbon dioxide permeation and sorption measure- ments, which also exhibit larger than expected reductions in solubility for the semicrystalline vs. amorphous samples. This study, which complements prior work, provides an initial look into the effect of crystallinity and morphology on the penetrant transport properties of PEF. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Poly(ethylene furanoate) (PEF) has recently been promoted as a potential bio-based alternative to fossil-fuel derived poly(ethylene terephthalate) (PET) [1e4], and has been the focus of much recent research [2,3,5e18]. A large motivation for studying PEF is that it exhibits significantly reduced barrier properties compared to PET. For example, amorphous PEF exhibits an 11 reduction in oxygen permeability [7], a 19 reduction in carbon dioxide permeability [12], and a 2.1 reduction in water permeability compared to amorphous PET [8,9,12]. While such data pertaining to the amor- phous morphology are needed to establish a baseline for compar- ison, industrial applications for PEF require the understanding of penetrant transport through both the semicrystalline and oriented morphologies. This study complements prior work in our group [3,7e13], and addresses the aforementioned need by examining the transport properties of water, oxygen, and carbon dioxide in semicrystalline PEF. Moreover, complementary crystallization characterization produces a comprehensive connection between crystallinity and transport in semicrystalline PEF. Such a connection has already been demonstrated for oxygen transport in semicrystalline vs. amorphous poly(propylene furanoate) (PPF) [19]; however, the data reported herein represent the first report for oxygen, carbon dioxide, and water transport in semicrystalline PEF. 2. Experimental methods 2.1. Materials and semicrystalline film preparation The poly(ethylene furanoate) (PEF) used in this study is the same material characterized in prior work [3,7e9,11,12], and the repeat structure for PEF is provided in Table 1. Amorphous films between 50 and 60 microns thick were prepared using the same melt-press/quench procedure described elsewhere [3,20], and the amorphous films were dried below the glass transition tempera- ture (i.e., T g ¼ 85  C [3]) under vacuum at 75  C overnight to remove sorbed water prior to the isothermal crystallization step. After drying at 75  C, the films were sandwiched between sheets of hard- temper aluminum foil or PTFE-coated aluminum foil and placed under a preheated aluminum block in a preheated oven at the isothermal crystallization temperature. After equilibrating under vacuum for 24 h at the desired crystallization temperature, the films were removed from the oven and allowed to quickly air cool to room temperature. Isothermal crystallization temperatures of 115 and 160  C were chosen for the current work to produce * Corresponding author. E-mail address: 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.2016.06.046 0032-3861/© 2016 Elsevier Ltd. All rights reserved. Polymer 98 (2016) 305e310