Polyethylenes Melt Index

Even though all these polyethylenes are around 1 MI,it can be seen
that at both temperatures,the LDPE has much lower viscosities
than those of LLDPE and mLLDPE.
The common question is how can all three materials have the same melt index?
The melt index,according to ASTM1238,for polyethylenes are measured at 190deg C at a load of 2.16kg.
The flow rate coming out of the die,measured in g/10min is the quoted melt index or MI.
This basically means that the melt index is a single point on the shear viscosity curve.
At 190 deg C,all three metarials crossover at this point.