Size-exclusion chromatography polyolefins

A viscosity online detector in a size exclusion chromatography (SEC) instrument allows for a universal calibration for polymers with known K- and a-values. For polymers that are only soluble at high temperature, e.g., polyolefines, high-temperature detectors are available, which can be operated up to 200°C. In addition to molar mass measurements, viscosity detectors have also been employed successfully to obtain structural information of branched polymers [28]. 

A combination of infrared spectroscopy with size exclusion chromatography has a wide application range in the characterization of copolymers, adhesives, impurity profiling in polymers and branching in polyolefines [60-65]. Commonly, the solvent used as a mobile phase absorbs strongly in the... 

Gel permeation chromatography (GPC) is also known as size-exclusion chromatography (SEC) and both names are used today in the literature. The GPC technique has been extensively used in the last 50 years and has contributed to the development of polyolefin catalysts, processes, and the improvement of resin performance. There exist good references that deal with the fundamentals of the technique [12, 13], calibration procedures [14-16], and the analysis of LCB [17-23], which still demands significant attention. 

Thus calibration of the apparatus with, for example, polystyrene standards with known values of K and a in the particular solvent at a particular temperature permits the absolute molecular mass to be calculated via the universal calibration method [9]. A further advantage of the detector is its ability to be used at temperatures up to 150°C, thus permitting the analysis of polyolefins. The study of branching in polymers is also possible with this system. This new detector probably represents the most significant advance in detectors for size exclusion chromatography in recent years. 

Keywords Crystallization analysis fractionation Field Flow Fractionation High performance liquid chromatography Hyphenated techniques Liquid chromatography Polyolefin analysis SEC-NMR coupling Size exclusion chromatography Temperature rising elution fractionation Two-dimensional liquid chromatography... 

Until about 40 years ago, the determination of the molar mass distribution was the prime objective of polymer fractionation by phase separation. Since the advent of size exclusion chromatography the need for such time consuming and essentially ineffective classic fractionation methods has disappeared. However, today chromatographic techniques are still incapable of producing large-size fractions of the order of 100 g and phase separation methods continue to be needed for the preparation of large amounts of narrow-distribution polymers that cannot be obtained by direct synthesis. The most important polyolefins, polyethylene and polypropylene, fall into this category and a discussion of fractionation by distribution between two... 

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