In this study

poly(vinilydene fluoride-co-hexafluoropropylene) (PVDF-HFP) was used for preparation of hydrophobic membranes using non-solvent induced phase inversion (NIPS) technique. PVDF-HFP copolymer with concentrations of 10 wt% and 12 wt% was prepared to investigate the effect of polymer concentration on pore structure

morphology

hydrophobicity and performance of prepared membranes. Besides

the use of two coagulation baths with the effects of parameters such as coagulant time

polymer type and concentration

and the amount of nonsolvent were studied. The performance of prepared membranes was evaluated based on the permeability and selectivity of oxygen and nitrogen from a gas mixture of nitrogen/oxygen under operating conditions of feed flow rate (1-5 L·min

-1

)

inlet pressure to membrane module (0.1-0.5 MPa) and temperatures between 25 and 45℃. The results showed that the use of two coagulation baths with different compositions of distillated water and isopropanol

coagulant time

polymer type and concentration

and the amount of non-solvent additive have the most effect on pore structure

morphology

thickness

roughness and crysta

llinity of fabricated membranes. Porosity ranges for the three fabricated membranes were determined

where the maximum porosity was 73.889% and the minimum value was 56.837%. Also

the maximum and minimum average thicknesses of membrane were 320.85 μm and 115 μm. Besides

the values of 4.7504×10

-7

mol·m

-2

·s

-1

·Pa

-1

0.525 and 902.126 nm were achieved for maximum oxygen permeance

O

2

/N

2

selectivity and roughness

respectively.