Patent ID: 7642330

Claim:
A method for selecting a polyolefin having a die swell within a preselected range, the method comprising: (a) obtaining from reference samples of a plurality of polyolefin batches, at least one data set for at least each of the tan (delta) measured at a first temperature, the tan (delta) measured at a second temperature, and melt index for each reference sample; (b) obtaining a die swell data set from the reference samples of the polyolefins; (c) correlating the tan (delta) measured at a first temperature, the tan (delta) measured at a second temperature, and melt index of said reference polyolefins and the die swell data set using a regression analysis to generate an equation for predicting the die swell as a function of the tan (delta) measured at a first temperature, the tan (delta) measured at a second temperature, and melt index; (d) obtaining from a non-reference polyolefin sample a value for each of the tan (delta) measured at a first temperature, the tan (delta) measured at a second temperature, and melt index and calculating the predicted die swell from the equation from step (c); (e) comparing the predicted die swell of step (d) to the die swell within the pre-selected range; and (f) rejecting the non-reference polyolefin when the predicted die swell for the nonreference polyolefin is outside of the pre-selected range of the die swell.