Fig. 2. SEM images of PP flat-sheet membranes using various PP concentrations. (PP concentration: (a) 10 wt%; (b) 16 wt%; (c) 22 wt%; (d) 28 wt%; (e) 34 wt%; (f) 40 wt%. Cross-section at magnification 5k and inserts showing the surface at magnification 2k).