On theother hand, PEI a highly branched aliphatic polyimine increased the zeta potential values over the entire pH range, rendering the surfaces to be positively charged at low pH.
This clearly showed how PEI enhanced the adsorption of lac dye on cotton fibres.
It could also be seen in this figure that isoelectric point (IEP) of PEItreated cotton fibres shifted to a pH value of approximately 8 with respect to IEP of the natural cotton fibres, a pH value of 2-3