Polymer-sieve adhesion

Formation of sieve-in-cage morphology is the most common indicator of poor polymer-sieve contact and MMMs with the morphology exhibit higher permeability but poor selectivities approaching those of the native polymer or even worse. Since enhancement of slectivities by molecular sieves can only be achieved in the absence of these defects, concerned efforts have been directed to enhance the adhesion between these two phases [27]. 

Chem. Descrip. Organophilic molecular sieve (sodium aluminosilicate) CAS 1318-02-1 EINECS/ELINCS 215-283-8 Uses Polymer additive for adsorbing low m.w. organics such as aliphatics, alcohols, aldehydes, ketones, chlorinated hydrocarbons, org. acids, anti aromatics for use in adhesives, coatings, and polymers component of food pkg. materials... 

A number of polymers have been embedded with zeolites to form mixed-matrix membranes however, like Barrer, many researchers note poor adhesion at the solid-polymer interface. The use of silane coupling agents to chemically link polymer to the zeolite particles, membrane formation under high-temperature conditions, and membrane annealing are common tools used to heal a poorly adhered, sieve-in-a-cage, interface. ... 

Several polymers other than PDMS and PVA have been examined for solid-polymer mixed-matrix pervaporation. An activated earbon-block polyether-amide mixed-matrix membrane was investigated for the separation of volatile organie eompounds (VOCs). An enhancement in both trichloroethane and water flux was noted, as well as increase in trichloroethane-water selectivity compared to the neat polymer. Zeolite-polyimide mixed-matrix membranes were explored for xylraie isomo- separation. Solid-polymer adhesion was poor, resulting in a sieve-in-a-eage morphology therefore, no separation properties that exceeded neat polymer membranes were identified. Methanol-toluene separation was successfully performed with NaX—Viton mixed-matrix membranes, though other solid-polymer combinations were attempted and failed to form an enhanced membrane. 

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