All the individual curves for a series of Mw's, temperatures,and shear rates can be incorprated into a master curve by plotting 7 7'Mo2 versus no PT where a is a constant near unity
where is a constant near unity versus into a master curve by plotting temperatures, and shear rates can be incorprated All the individual curvesfor a series of Mw's, h h h o o
All else being equal,broadening the molecular-weight distribution generally results in a polymer melt becoming non-Newtonian at lower values of shear rate,so by the time we come to those shear rates relevant to extruding etc.,the polymer is easier to handle with a lower viscosity. A small degree of branching of the polymer chains generally decreases the viscosity of a melt with the same average molecular weight since the branched chain is more compact.However,if the branching is extensive,for a reasonably high molecular weight(~106)the viscosity at low shear rates may be much higher,given the difficulties for these complicated interpenetrating structures to move.Imagine the structure as a collection of stars,i.e.*.Nevertheless,in almost all cases branching results in a lower viscosity at high shear rates
Polymer Solutions Solution Viscosity depends on same factors as polymer melts Viscosity also effect by concentration and solvent interaction effects
Polymer Solutions Viscosity also ef ect by concentration and solvent interaction ef ects Solution Viscosity depends on same factors as polymer melts
103 20 10 10 3.5 10 2 1 0.35 10 103 10 10 103 10 Shear rate,y/s The flow curve for 3%w/w polystyrene in toluene, for different molecular weights(shown in millions)
103 4 10 32 1 10 0.5 103 103 10 103 103 Shear rate,y/s The flow curve for polystyrene in toluene, Mw 20M,for different concentrations of polymer (shown as wt.%)