| Polymer membranes with selective permeations are excellent material candidates for many applications. Functional polymers containing ionic groups show high ionic conductivity and large water permeability, and they are also capable to block many harmful chemicals. However, the poor mechanical and dimensional stability of functional polymer membranes limits their use in many practical applications. In this study, nonwovens are employed to overcome the problems faced by the current polymer membrane technologies. Nonwoven fabrics show excellent mechanical strength and flexibility, and can serve as the structural host to enhance both the mechanical properties and functionality of polymer membranes.;To observe the properties and to explore the potential applications of polymer-filled nonwoven membranes, polymer-filled nonwoven membranes were first prepared and characterized using poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) and nylon nonwovens. Polymer-filled nonwoven membranes were prepared by filling the pores of nonwoven substrates with PAMPS, which was synthesized via radical polymerization and cross-linked to overcome the dissolution and undesirable swelling in water. PAMPS-filled nonwoven membranes showed enhanced dimensional stability and mechanical properties compared with PAMPS membranes without nonwovens. The conductivities of PAMPS-filled nylon nonwovens were slightly lower than those of PAMPS membranes. Compared with PAMPS membranes without nonwoven hosts, both linear and cross-linked PAMPS-filled nonwoven membranes exhibited lower vapor permeabilities for water, methanol, acetone, and dimethyl methylphophonate (DMMP). It was also found that PAMPS-filled nonwoven membranes showed higher selectivity of water over DMMP, a nerve agent simulant, than PAMPS membranes.;The structure-property relationships of polymer-filled nonwoven membranes were studied using different functional polymers, PAMPS, poly(styrenesulfonic acid) (PSS), and poly(methacrylic acid) (PMA). Permeabilities and selectivities of PAMPS, PSS and PMA were measured and it was found that PSS, which has the highest polymer chain flexibility, showed the largest diffusion coefficient, which resulted in highest permeabilities for different permeants. It was also found that the cross-linking of functional polymers decreased the membrane permeabilities due to the reduced physical interactions formed by ionic attraction. The effect of nonwovens on the permeabilities and selectivities of polymer-filled nonwoven membranes was also studied using polypropylene nonwovens with different structures. Although the presence of nonwoven hosts significantly influenced the membrane permeabilities and selectivities, the changes of nonwoven structures such as fiber denier and basis weight did not drastically affect the membrane properties. Polymer-filled nonwoven membranes were further hot-pressed to increase the membrane uniformity, and hot-pressed membranes showed lower permeability and higher mechanical properties than un-pressed ones, indicating that the hot press process was effective to control membrane properties.;Based on the results of the structure-property relationships, hot-pressed polymer-filled nonwoven membranes were selected to systematically evaluate the chemical protection performance, and NafionRTM, one of the well-known chemical protection membranes, was used for comparison. It was found that hot-pressed polymer-filled nonwoven membranes showed lower vapor permeations to different simulants of chemical warfare agents and higher water-to-simulant selectivities compared to NafionRTM. Therefore, it was concluded that hot-pressed polymer-filled nonwoven membranes were promising candidate for chemical protection application. |
