Quantifying Relationships among the Molecular Weight Distribution, Non-Newtonian Shear Viscosity, and Melt Index for Linear Polymers
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- 作者：Kevin C. Seavey ; Y. A. Liu ; Neeraj P. Khare ; Tim Bremner ; and Chau-Chyun Chen
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2003
- 出版时间：October 15, 2003
- 年：2003
- 卷：42
- 期：21
- 页码：5354 - 5362
- 全文大小：149K
- 年卷期：v.42,no.21(October 15, 2003)
- ISSN：1520-5045
文摘
This paper presents methodologies to quantify the relationships among the molecular weightdistribution (MWD), steady-shear non-Newtonian viscosity (i.e., flow curve), and melt index (MI)of three linear low-density polyethylenes manufactured using the same technology. With theaid of computer-aided process simulation tools (such as POLYMERS PLUS), polymer producerscan predict accurately the MWD from manufacturing conditions. Our methodologies help thepolymer producers to extend their simulation model to predict flow curves and MI from theMWD. To do this, this paper employs (1) a modified Carreau-Yasuda (CY) model or Bersted'spartition model to relate the MWDs and flow curves, (2) Bremner and Rudin's model to relatethe weight-average molecular weight (MWW) and MI, and (3) Rohlfing and Janzen's model torelate the flow curve and MI. We show that the Carreau-Yasuda, Bersted, and Bremner andRudin models work very well for correlating our data, predicting flow curves that average 3-7%error and MI values that average 2% error. In addition, for the case in which we lack MI data,we use the CY or Bersted model predictions of the flow curve to generate MI values throughRohlfing and Janzen's model. These predictions are very good, averaging only 0.5-3% error.We also show how to use the CY or Bersted model and Rohlfing and Janzen's melt-indexermodel to estimate closely the low shear rate region of the flow curve using MWD/MI data alone.This case corresponds to one in which we lack flow curve data. Last, we provide practicalguidelines for polymer manufacturers who want to predict the flow curve and MI using theMWD.