Treatment was initially melamine, but the advent of epoxy sizing in the early 80s has improved heat and chemical resistance. 2 Monofilament weaves, although sometimes limited to low pressure operation, are useful in certain applications. Adhesives must be somewhat flexible when set, and have certain manufacturing related handling characteristics. These requirements have limited the available choices. Improvements are considered proprietary.
Typical adhesives have a long-term upper temperature limit below that of some of the membranes.
Solvent compatibility may also make the adhesive the weak link. While substantial progress has been made, adhesives remain an area of focus for sepralator improvement. This design has changed little over the years and still predominates in water purification and most process applications, due to the general success of the design. However the size and configurations available in mesh net spacers have expanded in recent years. The results of the Levy and Earle study is just the most recent confirmation of the long established fact that the presence of a mesh spacer over a crossflow membrane surface maintains higher flux.