Preparation and study of crosslinked polyurethane films to fractionate toluene: n-heptane mixtures by pervaporation
Preparation and study of crosslinked polyurethane films to fractionate toluene: n-heptane mixtures by pervaporation
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DOI：
10.1016/s1383-5866(00)00150-7
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发表时间：
2001-03
影响因子：
8.6
通讯作者：
D. Roizard;A. Nilly;P. Lochon
中科院分区：
文献类型：
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作者：
D. Roizard;A. Nilly;P. Lochon
聚（醚氨基甲酸酯）和聚（酯氨基甲酸酯）嵌段共聚物（记为PEG和PCL）由脂族二异氰酸酯和醚或酯低聚物二醇在一个或两个合成步骤中由封端的异氰酸酯（路线1）或羟基（路线2）官能化的低聚物制备。用于共聚的NCO与OH基团的比率导致制备化学交联的聚氨酯膜。用DSC表征了它们的微相分离结构，并记录了软嵌段的Tg和Tm。通过对甲苯-正庚烷混合物的吸附、扩散和渗透蒸发实验，研究了聚合物膜的分离性能。实验表明，强甲苯选择性的所有膜进行的整个浓度范围内。根据路线1制备的膜表现出比通过路线2制备的膜更低的吸附度和通量，差异可以容易地与通过路线2实现的更低的交联密度相关;另一方面，两种膜类型的选择性几乎相同。在无限稀释的两种纯溶剂的扩散系数，确定从实验中进行的瞬态和甲苯系数被发现稍微超过正庚烷中的交联度较低的聚氨酯网络。芳香族化合物的优先渗透蒸发基本上被证明是由于吸附步骤;然而在所有情况下，吸附选择性高于渗透蒸发，这意味着扩散步骤实际上更有利于脂肪族组分。
Poly (ether urethane) and poly(ester urethane) segmented copolymers (noted PEG and PCL) were prepared from aliphatic diisocyanate and ether or ester oligomer diols in one or two synthetic steps either from end capped isocyanates (route 1) or hydroxyl (route 2) functionalised oligomers. The ratio of NCO to OH groups used for the copolymerisation led to the preparation of chemically crosslinked polyurethane films. Their microphase-separated structures were characterised by DSC and the Tgand Tmof the soft blocks was recorded. The separation properties of the polymer films were investigated by sorption, diffusion and pervaporation (PV) experiments with toluene–n-heptane mixtures. The experiments demonstrated strong toluene selectivity for all the films carried out on the whole range of concentration. The membranes prepared according to route 1 exhibited lower sorption degrees and fluxes than the ones prepared by route 2, differences that could be easily related to the lower crosslinking density achieved by route 2; on the other hand the selectivity of both membrane types was almost the same. The diffusion coefficients at infinite dilution of both pure solvents were determined from experiments carried out in the transient state and the toluene coefficient was found to slightly exceed the n-heptane one in the less crosslinked urethane networks. The preferential pervaporation of the aromatic compound was basically shown to be due to the sorption step; nevertheless in all cases the sorption selectivity was higher than the pervaporation one which means that the diffusion step was in fact more favourable to the aliphatic component.