Comparison of different methods for the investigation of the short-chain branching distribution of LLDPE

The aim of this paper is the comparison of three different methods for the investigation of the short-chain branching distribution of linear low-density polyethylene and the analysis of the composition of polyolefin blends. The three methods to be compared are analytical temperature rising elution fractionation (TREF), the commercialized Crystaf(R) technique, and a method based on differential scanning calorimetry with a special sample preparation procedure. This paper also discusses the specific advantages and disadvantages of each method by comparing the results for selected Ziegler-Natta and metallocene LLDPE (ZN-LLDPE and mLLDPE, respectively) and a model blend of LLDPE, HDPE and PP. As is demonstrated for these materials the three analytical methods yield comparable results with respect to the comonomer distribution of LLDPE. For the investigation of polyolefin blends the combination of the three methods is found to be recommendable, especially if polymers with high degrees of supercooling like polypropylene are involved. (C) 2000 Elsevier Science Ltd. All rights reserved.