Cross-sectional Images of Membranes by SEM

Boom et al. [7] studied a PES/PVP (PVP as an additive) hollow fiber membrane by electron microscope and also observed a nodular structure. On the active surface. 

Xu et al. [11] studied the effects of both N,N-dimethylacetamide (DMAc) as a solvent additive in an internal coagulant (water) and acetic acid as a nonsolvent additive in a dope solution (PEI in DMAc) on the morphology and performance of poly(etherimide) (PEI) hollow fiber membranes for UF. Cross-sectional pictures were taken by SEM. The authors observed nodular structures on the inner and outer edges of the cross section when the amount of the acetic acid in the dope solution was increased. Pure water permeation flux increased when the nodules appeared. 

Fusaoka et al. [12] observed a structure composed of fused and deformed polymeric spheres using FE-SEM in a cross section of the membranes, cast and dried from solutions of poly(l-trimethyl-silyl-l-propyne), poly(4-methyl-l-pentene), and some other polymers. 

Membranes prepared by the dry-wet phase inversion method from glassy polymers are composed of polymeric spheres. 

The interstitial void spaces are connected to the openings at the membrane surfaces, forming capillary pores in the membranes. 

---