BACKGROUND: The effects of shear rate induced molecular orientation in polymeric based asymmetric membranes on performance, structural details, key properties, morphologies and pore size distribution were studied. Asymmetric membranes fabricated at five different potential shear rates ranging from 93.33466.67 s-1 were evaluated based on nanofiltration test. The use of SpieglerKedem, steric-hindrance pore and TeorellMeyersSievers models enables an assessment to be made of the relationship between shear rates and membranes properties. RESULTS: Experimental and modeling results show that there is a significant correlation between shear and membrane characteristics, whereby as shear rate increases, the separation performances of nanofiltration membranes increase until an optimum (critical) level of shear is achieved. Beyond the optimum shear, the deterioration inmembrane performance suggests that there exists an optimum shear rate which produces optimal structural details, key properties, morphologies and pore size distributions. CONCLUSIONS: Results showed that a skinned-oriented highly selective charged asymmetric low pressure nanofiltration (ALPNF) membranewas successfully developed. The optimum shear rate (critical shear) was found to be 233.33 s-1. At the optimum shear rate, the fabricated ALP-NF membranes produced the finest properties, morphology and narrowest pore distributions. The positive improvement in performance properties of ALP-NF membrane provides the potential for producing a highly selective NF membrane for different applications in the future. (C) 2011 Society of Chemical Industry