Morphological, chemical and electrical characterization of a family of commercial nanofiltration polyvinyl alcohol coated polypiperazineamide membranes

•3 TFC tubular NF membranes from PCI, AFC30, AFC40 and AFC80, have been thoroughly characterized.•According to XPS they have PPA active layers coated with PVA increasingly as AFC80→ AFC40→AFC30.•Retention of 1:1, 1:2 and 2:1 salts show that more negative charges appear when PVA increases.•More PVA increases wettability. Highest PVA coverage corresponds to the widest pore size.•Wider pores give higher permeabilities, lower roughness and higher fractal dimensions.