Surface Modification by Heat Treatment

Membrane surfaces can also be modified by heat treatment. The PES HFMs were prepared by dry-wet spinning method and heated in an oven at 120,150, and 180°C. The membrane shrank by heating. It was noticed that pore size decreased from 8.16 nm for untreated hollow fiber to 3.8 nm with 1 minute heating and then increased to about 6 nm with 5 min heating at 150°C. With an increase in heating temperature, the pore size of the membrane decreases [77,78]. Charkoudian et al. reported increased levels of protein adsorbed in thermally treated poly-acrylamide-modified PVDF microporous membranes in comparison to thermally untreated polyacrylate-modified membranes [79]. 

Grafting can also be applied for the surface modification of the membrane. Although the method should work for any polymeric materials, most of the recent works on membrane surface graft polymerization were on polyamide thin-film composite (TFC) membranes or porous polypropylene membranes. 

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