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