Summary: New crystallization procedures have been developed for the analysis of the chemical composition distribution in polyolefins by pumping a small flow of solvent during the crystallization cycle. One of the new techniques, crystallization elution fractionation (CEF) combines the separation power of TREF and CRYSTAF and has been shown to provide very fast analysis of the composition distribution.

Crystallization Elution Fractionation has been optimized to improve resolution power and reduce co-crystallization. Most important step to be optimized is the first separation cycle of Dynamic Crystallization which can be investigated with the help of Crystallization Analysis Fractionation experiments. A new approach to reduce co-crystallization and improve resolution is presented by applying successive cooling and heating cycles in a long column. The new process known as Multiple Crystallization Elution Fractionation adds extended separation at each cooling and heating cycles.

Summary: A compact automated instrument has been developed for measuring the bivariate distribution by TREF fractionation and subsequent GPC analysis of the fractions in a single run. The configuration of this instrument and its operation principles are covered here. High resolution TREF fractionation of HDPE and fast methods with overlapped GPC injections are also discussed. Future developments, such the addition of comonomer or molar mass sensitive detectors, as well as operation in GPC -TREF mode for broad MWD resins are outlined.

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Very powerful triple detector high-temperature gel permeation chromatography (HT-GPC) systems equipped with concentration, viscosity, and multiple angle light scattering detectors can be found in many polyolefin characterization laboratories. However, the complexity and sometimes lack of robustness of some detection methods often result in failure to achieve the required precision and long-term reliability to properly support the industrial needs. Two methods for data processing in triple detector HT-GPC of polyolefins are here described aiming at overcoming those difficulties, specifically those related to the application of multiple angle light scattering. In the first place, we propose here a data processing method using light scattering data collected at only one angle, with application of a dissymmetry correction based on an estimate of the molecular size from the hydrodynamic volume given by the universal calibration. This method (SALS DC : single-angle light scattering with dissymmetry correction) is simple and robust for molar mass distribution and averages. Long chain branching detection and quantification is another field plagued with lack of precision and inconsistency problems, due to the difficulty in collecting reliable radius of gyration (Rg) data using MALS, for calculation of the g-index. A novel approach to estimate the g-index, based on point-by-point calculation of the gpcBR index is here described and evaluated.