General and more precise relationships between molecular weight, blend ratio, and melt index of binary polyethylene blends

Abstract

Simpler, cheaper, and fast methods to characterize material properties are important in industrial plants. One of these properties is molecular weight which is measured generally by size exclusion chromatography, an expensive method and also limited for polyolefins which have few solvents. Melt flow index (MFI) measurement is simple, cheap, and rapid that could be a considerable method to estimate M̄w of polymers. In this work, mathematical correlation between MI* (a new defined MFI),_first melt dropping of blend (t 1), weight fraction (wi) and M̄w in binary polyethylene blends, PE/PE wax, has been investigated by using a new device. Results show that relationships MI* and t1 with wi of the blended materials follow a modified Arrhenius equation (Wong equation) and also new non-Arrhenius equations for prediction of MI of blends have been investigated. We proposed a modified molecular weight (M̄m) for Bremner and Rudin's equation (Bremner et al, J Appl Polym Sci 1990, 41, 1617), which is used in 1/MI* and t1 correlations with molecular weight of polymer. © 2008 Wiley Periodicals, Inc.