Microstructure and modeling of uniaxial mechanical properties of Polyethersulfone nanocomposite ultrafiltration membranes

Polyethersulfone (PES) nanocomposite membranes are some of the emerging ultrafiltration technologies that have promising applications in gas separation and wastewater treatment due to their unique microporous struc-ture and cheapness. However, the effect of nanofiller additives on their mechanical and viscoelastic properties is still missing and these fundamentals should be known to designers and manufacturers for potential upscal-ing. In this context, this research aims to study the uniaxial mechanical behaviors of PES membranes and their nanocomposites (CNTs/PES and Graphene/PES), and then to model their mechanical characteristics based on the results of mechanical experiments. In order to achieve that, four batches from CNTs/PES and Graphene/PES nanocomposite membranes with different concentrations of nanofillers (0.01-0.04 wt.%) were prepared using a solution casting method and a tape casting process. Also, another neat PES batch was prepared for comparison. The pore topology of the synthesized membranes was observed using SEM. Afterwards, the mechanical tensile specimens were cut from the synthesized membranes and tested according to standard ASTM 638M-3 using a uniaxial universal testing machine. Finally, a nonlinear uniaxial stress-strain model was built to simulate the mechanical performance of the fabricated membranes using the generalized Maxwell model. The results showed that the mechanical properties of the membranes were reduced significantly by additives (up to 26% for CNTs and 57% for GA compared with neat batch) because of the changes in the pore topology (orientation, size, and distribution) of the prepared membranes,whereas the modeling results showed that the constitutive model is valid for deducing the uniaxial stress-strain curves of PES membrane and its nanocomposites membranes with a high predictability and average deviation estimated at 0.715% (PES), 0.302% for CNTs/PES and 0.164% for GA/PES membranes.

Automated summary

The mechanical properties of PES membranes and their nanocomposites were studied, showing a significant reduction in mechanical properties due to the addition of nanofillers altering the pore topology. The constitutive model effectively derived the uniaxial stress-strain curves of PES membranes and their nanocomposites with high predictability.