Cava D, Sammon C, Lagaron J M
Institute of Agrochemistry and Food Technology (IATA) CSIC, Apdo Correos 73, Burjassot, 46100, Spain.
Appl Spectrosc. 2006 Dec;60(12):1392-8. doi: 10.1366/000370206779321382.
Attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy has been advantageously used to carry out a simultaneous study of the effect of temperature on sorption, diffusion, swelling rate, and swelling rate factor of ethylene-vinyl alcohol (EVOH) cast films with three different ethylene contents (29, 38, and 44 mol % of ethylene). While the sorption and swelling levels at equilibrium did not appear to be affected by temperature in the temperature range studied, the effect of increasing ethylene content was seen to largely decrease the sorption-induced swelling. It should be noted that all samples showed significant levels of swelling ( approximately 60% in the copolymer with lowest ethylene content), suggesting that films obtained by solution-casting generate polymer morphologies that are far more prone to uptake water than typical melt-extruded ones. It was also observed that increasing the ethylene content led to a reduction of the "effective" D value, while raising the temperature increased diffusion and swelling rate factor. The activation energies obtained for the diffusion of water were relatively low and similar to the typical energy barrier required to break hydrogen bonding interactions, suggesting that water molecules diffuse very easily across the film due to its high chemical affinity with the polymer matrix.
衰减全反射傅里叶变换红外（ATR-FT-IR）光谱已被有效地用于同时研究温度对三种不同乙烯含量（乙烯含量分别为29%、38%和44摩尔%）的乙烯-乙烯醇（EVOH）流延膜的吸附、扩散、溶胀速率和溶胀速率因子的影响。在所研究的温度范围内，平衡时的吸附和溶胀水平似乎不受温度影响，但乙烯含量增加的影响表现为显著降低吸附诱导的溶胀。应当指出的是，所有样品均表现出显著的溶胀水平（乙烯含量最低的共聚物中约为60%），这表明通过溶液流延得到的薄膜所产生的聚合物形态比典型的熔融挤出薄膜更容易吸水。还观察到，乙烯含量增加导致“有效”D值降低，而温度升高则增加扩散和溶胀速率因子。水扩散获得的活化能相对较低，与打破氢键相互作用所需的典型能垒相似，这表明由于水分子与聚合物基体具有高化学亲和力，水分子很容易在薄膜中扩散。
