Abstract:  The applicability of apparent viscosity in the investigation of synergistic interaction between two different polymerswas studied. Simple concentration additivity and viscosity additivity are the two commonly used criteria for judging the synergistic effect in binary biopolymer systems. When the viscosity indexes of both polymers are greater than one, the viscosity of mixture calculated from viscosity additivity is lesser than that calculated from concentration additivity. When the viscosity indexes of both components are less than one, the viscosity of mixture calculated from viscosity additivity is greater than that calculated from concentration additivity. The relationship between two methods is quite complex when the viscosity index of one component is greater than one and the other one is less than one. When the viscosity indexes of two components are both equal to one, the two methods are identical.

Key words: apparent viscosity, compounding, synergistic interaction