Composite hot-melt/epoxy potting architecture for high-pressure sorp-vection hollow fiber modules

The practical limit of a hollow fiber membrane module is often set by module-level structural constraints rather than by intrinsic membrane properties, but potting design receives little attention in the membrane literature. This limitation is particularly pronounced for modules with a soft, highly swellable selective layer in aggressive feeds using conventional single-epoxy potting. Here we report a composite hot-melt/epoxy potting architecture that enables mechanically stable sealing and extended operation of hollow fiber modules used for liquid-phase separation of cyclic siloxanes from silicone oil. The novel architecture, a compliant thermoplastic hot-melt inner plug surrounded by a high-temperature epoxy, is compared directly with less compatible clear-epoxy and even more durable black-epoxy modules under identical pressurized liquid conditions. Whereas single-epoxy modules show pressure-dependent interfacial leakage and limited lifetime, the composite suppresses polymer--epoxy debonding, and raises the leak-free limit to 900~psia, with stable operation beyond 2000~h at 500~psia. Fluorescence leak-spot visualization confirms that the composite shifts the dominant failure mode away from circumferential debonding at the polydimethylsiloxane (PDMS)--epoxy interfaces. Notably, the thermoplastic component also renders the module thermally reworkable if necessary. A demonstration of this capability is provided wherein reheating in place allows recovery of the separation factor from a degraded value to 13.07 without complete remanufacturing. While leak-free operation remains the ultimate goal, this reworkable option provides a practical safety net as development continues. These results establish potting architecture as a first-order structural design parameter governing the reliability of high-pressure sorp-vection hollow fiber modules.