Burgess, Steven K. Lee, Jong Suk Mubarak, Christopher R. Kriegel, Robert M. Koros, William J. 2024-01-20T07:02:37Z 2024-01-20T07:02:37Z 2021-09-05 2015-05-18 0032-3861 https://pubs.kist.re.kr/handle/201004/125433 This study investigates the phenomenon of caffeine antiplasticization of amorphous poly(ethylene terephthalate) (PET). Oxygen and carbon dioxide permeation measurements at 35 degrees C reveal significant barrier improvement (e.g., >3x for PET mixed with similar to 10.7 wt% caffeine) for all PET/caffeine samples studied. Penetrant solubility and diffusivity estimates are used to deconvolute the relative transport contributions to the overall barrier reduction determined via permeation testing. Density values provide a direct measure of the reduced free volume for the antiplasticized samples vs. neat PET, and provide a basis for understanding the barrier improvement. Further investigation via dynamic mechanical analysis of the sub-ambient beta relaxation reveals that the diffusion reductions for the antiplasticized samples originate from caffeine suppressing the phenyl ring flipping mechanism known to occur in glassy PET. The data reported in this paper suggest that antiplasticization of PET occurs via a combination of both "hole filling" and chain mobility restriction mechanisms, and that the relative mechanistic contributions to transport reduction depend largely on the penetrant solubility and diffusivity within the polymer matrix. (C) 2015 Elsevier Ltd. All rights reserved. English ELSEVIER SCI LTD SECONDARY RELAXATION PROCESSES TEREPHTHALATE-ADDITIVE BLENDS OXYGEN-BARRIER PROPERTIES SOLID-STATE NMR POLYETHYLENE TEREPHTHALATE POLY(ETHYLENE FURANOATE) GLASS-TRANSITION NONCOOPERATIVE RELAXATIONS WATER SORPTION POLYMERS Caffeine antiplasticization of amorphous poly(ethylene terephthalate): Effects on gas transport, thermal, and mechanical properties Article 10.1016/j.polymer.2015.03.051 1 POLYMER, v.65, pp.34 - 44 POLYMER 65 34 44 scie scopus 000355064000006 2-s2.0-84927534517 Polymer Science Polymer Science Article SECONDARY RELAXATION PROCESSES TEREPHTHALATE-ADDITIVE BLENDS OXYGEN-BARRIER PROPERTIES SOLID-STATE NMR POLYETHYLENE TEREPHTHALATE POLY(ETHYLENE FURANOATE) GLASS-TRANSITION NONCOOPERATIVE RELAXATIONS WATER SORPTION POLYMERS Barrier Transport Oxygen