This article considers a previously overlooked feature in carbon molecular sieve (CMS) membranes that we term a “hyperskin” present at the outermost region of dense CMS selective layers. Such a feature with much lower permeability, but similar selectivity compared to the bulk of the skin, reduces CMS hollow fiber permeance below that predicted from corresponding dense films. Effects of the hyperskin are considered for CMS hollow fibers with low skin thicknesses based on two polyimide precursors – Matrimid^® and 6FDA:BPDA-DAM. Although the fundamental formation mechanism for the hyperskin feature suggests its existence on virtually all CMS membranes, its impact on transport properties is shown to differ dramatically, depending on the detailed characteristic properties of the specific CMS membrane. Indeed, for hollow fibers with very low nominal resistance (i.e. $\frac{\mathrm{Selective\; layer\; thickness\; determined\; by\; SEM}}{\mathrm{Intrinsic\; permeability\; of\; thick\; dense\; CMS\; films}}$), the observed permeance only reaches a small fraction of the predicted permeance. The selectivity between different gas penetrants, however, is not altered by the presence of this hyperskin. While identifying this issue is the major focus of this article, strategies to address this limitation, without compromising the molecular sieving properties of CMS membranes are briefly discussed.

本文考虑了碳分子筛（CMS）膜中以前被忽略的特征，我们称其为致密CMS选择性层最外层的“超皮”。与皮肤的大部分相比，这种具有低得多的渗透性但具有相似选择性的特征将CMS中空纤维的渗透率降低到低于由相应的致密膜所预测的渗透率。在hyperskin的影响被认为是基于两个聚酰亚胺前体低皮肤厚度CMS的中空纤维-的Matrimid ^®和6FDA：BPDA-DAM。尽管超皮肤特征的基本形成机理表明它实际上存在于所有CMS膜上，但根据特定CMS膜的详细特征，其对转运特性的影响显示出显着不同。实际上，对于标称电阻非常低的中空纤维（即$\frac{\mathrm{选择性层厚度由SEM确定}}{\mathrm{厚致密CMS膜的本征渗透率}}$），观察到的磁导率仅达到预测磁导率的一小部分。但是，这种超皮肤的存在不会改变不同气体渗透剂之间的选择性。虽然确定此问题是本文的主要重点，但简要讨论了在不损害CMS膜分子筛分特性的情况下解决这一局限性的策略。