Method of selecting polyolefins based on rheological properties

A method for manufacturing a blow-molded article having a die swell within a pre-selected range, the method comprising:

• (a) obtaining from reference samples of a plurality of polyolefin batches a data set for at least one property, other than die swell, of the polyolefin;
• (b) obtaining a die swell data set from the reference samples of the polyolefin;
• (c) correlating the at least one property and the die swell data set using a regression analysis to generate an equation for predicting the die swell as a function of the at least one property from step (a);
• (d) obtaining from a non-reference polyolefin sample a value for each variable in the equation from step (c) 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) blow-molding the polyolefin sample, having the predicted die swell within the pre-selected range, to form the blow-molded article.

A method of controlling a polyolefin reactor, the method comprising:

• (a) obtaining from reference samples of a plurality of polyolefin batches a data set for at least one property, other than die swell, of the polyolefin;
• (b) obtaining a die swell data set from the reference samples of the polyolefin;
• (c) correlating the at least one property and the die swell data set using a regression analysis to generate an equation for predicting the die swell as a function of the at least one property from step (a);
• (d) obtaining from a non-reference polyolefin sample a value for each variable in the equation from step (c) and calculating the predicted die swell from the equation from step (c);
• (e) comparing the predicted die swell of step (d) a control value for die swell;
• and
• (f) modifying at least one reactor condition to reduce a difference between the control value and the predicted die swell for the polyolefin sample from the reactor.