The Instrument Spreading Correction in GPC. I. The General Shape Function Using a Linear Calibration Curve

An experimental technique, crystallization analysis fractionation (Crystaf), is used to analyze compositional uniformity of ethylene/α‐olefin copolymers and isotactic polypropylene. A computerized method for quantifying Crystaf data is developed based on resolution of Crystaf curves into their elemental components, with each component representing a fraction of the polymer with the same degree of chain imperfection. This analysis of Crystaf curves gives three parameters characterizing crystallizable polymer material: (a) the number of compositionally uniform components, (b) properties of each compositionally uniform component (in the case of ethylene/α‐olefin copolymers, the comonomer content), and (c) the quantity of each component. Crystaf analysis of several ethylene/1‐hexene copolymers produced with supported Ti‐based Ziegler‐Natta catalysts shows the existence of two groups of copolymer components. The first group includes components with low comonomer content, in the Crystaf analysis they precipitate at high temperatures as several relatively sharp peaks. The second group includes components with high comonomer contents; they precipitate at much lower temperatures, as a broad overlapping group of peaks. The peak resolution technique was applied to analysis of ethylene/α‐olefin copolymers prepared with a supported catalyst at different temperatures, a copolymer produced with a pseudo‐homogenous Ziegler‐Natta catalyst, and to isotactic polypropylene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Section: Peak Shapementioning

confidence: 99%

Analysis of polyolefins and olefin copolymers using Crystaf technique: Resolution of Crystaf curves

Kissin

Fruitwala

2007

“…Extrapolation of these curves to zero conversion, according to eqs. (10) and (14), makes it possible to determine C ai , the concentration of every active center separately, and also the total concentration of the polymerization centers, ⌺C ai .…”

Section: Resultsmentioning

confidence: 99%

The nature of the organoaluminum compound and the kinetic heterogeneity of active sites in lanthanide‐based diene polymerization

Sigaeva

Usmanov

Заиков

et al. 2003

ABSTRACT:The influence of the organoaluminum compound on the kinetic heterogeneity of active sites in lanthanide-based diene polymerization was investigated. It was found that the heterogeneity of investigated catalytic systems was shown in the existence of four types of active centers. They were formed at the beginning of the polymerization process and produced macromolecules with lengths that were definite for each type of active center. The nature of the organoaluminum compound greatly influenced the kinetic activity of the polymerization centers. A method for analyzing the curves' maximums of distribution on kinetic activity and the change in kinetic activity of every type of active centers is proposed. This method allows calculating the concentration values for each type of active center separately.

“…9 Chromatograms and the obtained values of molecular weights were corrected for instrumental spreading, as described in ref. 10 . The calculation of distribution function on kinetic heterogeneity of the NdCl 3 3L-OAC catalytic system was carried out by Tikhonov regularization method.…”

Section: Methodsmentioning

confidence: 95%

The influence of the nature of organoaluminum compound on kinetic heterogeneity of active sites in lanthanide‐based diene polymerization

Sigaeva¹,

Usmanov²,

Budtov³

et al. 2002

ABSTRACT:The influence of organoaluminum compound on kinetic heterogeneity of active sites in lanthanidebased diene polymerization was investigated. It was shown that heterogeneity of investigated catalytic systems was displayed in the existence of four types of active centers. They are formed at the beginning of the polymerization process and produce macromolecules with lengths that are definite for each type of active centers. The organoaluminum compound's nature greatly influences the kinetic activity of polymerization centers. The method of analysis of the curves' maximum distribution on kinetic activity and the change of kinetic activity of every active centers' type were proposed, which permits the calculation of values of concentration for each type of active center separately.