Water Vapor Sorption and Diffusivity in Bio-Based Poly(ethylene vanillate)—PEV

Abstract

The dynamic and equilibrium water vapor sorption properties of amorphous and highly crystalline poly(ethylene vanillate) (PEV) films were determined via gravimetric analysis, at 20 °C, over a wide range of relative humidity (0–95% RH). At low RH%, the dynamic of the sorption process obeys Fick’s law while at higher relative humidity it is characterized by a drift ascribable to non-Fickian relaxations. The non-Fickian relaxations, which are responsible for the incorporation of additional water, are correlated with the upturn of the sorption isotherms and simultaneously the hysteresis recorded between sorption and desorption cycles. The sorption isotherms of amorphous and highly crystalline PEV are arranged in the same concentration range of that of PET proving the similarity of the two polyesters. Water diffusion coefficients, whose determination from individual kinetic sorption/desorption curves required treatment with the Barens–Hopfenberg model, were demonstrated to be ≈ 10× higher for amorphous PEV compared to amorphous PET. Such a difference originates from the enhanced segmental flexibility of PEV chains.

All-Atom Molecular Dynamics Simulations on a Single Chain of PET and PEV Polymers

“…Our obtained T g value for PET of 345 K was very close to the previous prediction of 342 K [ 11 ] but somewhat lower than the available experimental values by 5–8 K [ 11 , 27 , 28 ]. Although the T g of PEV was first reported here at 353 K higher than that of PET in line with the experimental data (356 K) [ 10 , 11 ], it was 6–7 K more elevated than that of the others [ 10 , 29 ]. In addition, the density of PET was in a range of 1.30–1.40 g/cm 3 [ 26 , 30 ].…”

Prediction of the Glass Transition Temperature in Polyethylene Terephthalate/Polyethylene Vanillate (PET/PEV) Blends: A Molecular Dynamics Study

“…The results in Figure 4 show T g values of 344–347 K for PET/PEV blends, in the same range for PEV (346 K) and PET (345 K), and which are close to the experimental [ 11 , 12 , 28 ] and computational [ 21 , 29 ] studies ( Table 2 ). The T g values for all PET/PEV ratios were not significantly different, unlike the PMMA/PS blends, which showed an increase in T g as the percentage of PS was enhanced [ 19 ].…”

“…The predicted Tg of each system was the temperature at the intersection between the two trending lines that fitted from low temperatures of 100-300 K to high temperatures of 400-600 K. It should be noted that the Tg prediction by monitoring the specific volume or density of a system per temperature has been used successfully in several polymers [13,14,20,21,26,27]. The results in Figure 4 show Tg values of 344-347 K for PET/PEV blends, in the same range for PEV (346 K) and PET (345 K), and which are close to the experimental [11,12,28] and computational [21,29] studies (Table 2). The Tg values for all PET/PEV ratios were not significantly different, unlike the PMMA/PS blends, which showed an increase in Tg as the percentage of PS was enhanced [19].…”

“…PEV (TV05) TV14 TV23 TV32 TV41 MD simulation 345, 345 [21], 342 [12] 346, 353 [21] 344 346 345 347 Experiment 353 [12], 350 [29] 347 [11], 348 [28], 356 [12] NA…”

“…Nonetheless, the synthesis of PET/PEV blending is required to validate our T g -predicted model. Experiment 353 [12], 350 [29] 347 [11], 348 [28], 356 [12] NA…”