Polymer Char

Valencia, Spain

Polymer Char

Valencia, Spain
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Cheruthazhekatt S.,Stellenbosch University | Mayo N.,Polymer Char | Monrabal B.,Polymer Char | Pasch H.,Stellenbosch University
Macromolecular Chemistry and Physics | Year: 2013

Preparative temperature rising elution fractionation (prep TREF) suffers from co-crystallization effects and, therefore, cannot provide reliable chemical composition distribution (CCD) information. This limitation can be overcome when prep TREF is combined with further fractionation methods such as crystallization elution fractionation (CEF) or high-temperature solvent-gradient-interaction chromatography (HT-SGIC) as a new approach. By CEF, significant amounts of (co-crystallizing) amorphous ethylene-propylene (EP) copolymer are identified in semicrystalline TREF fractions of a heterophasic ethylene/propylene copolymer (HEPC). Complete compositional fractionation with no influence of crystallization effects is accomplished by HT-SGIC. Prep TREF-HT-SGIC is found to be the most selective and suitable method for the fast and complete CCD analysis of such complex EP copolymers with CEF providing complementary information. A new method for the chemical composition separation of ethylene-propylene copolymers by combining prep TREF with crystallization elution fractionation (CEF) and high-temperature solvent gradient interaction chromatography (HT-SGIC) is proposed. CEF is based on crystallizability, and separates amorphous and semi-crystalline components. HT-SGIC separates strictly according to chemical composition and is thus complementary to CEF making TREF-CEF-SGIC a very useful the combination. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ortin A.,Polymer Char | Lopez E.,Polymer Char | Monrabal B.,Polymer Char | Torres-Lapasio J.R.,University of Valencia | Garcia-Alvarez-Coque M.C.,University of Valencia
Journal of Chromatography A | Year: 2012

Infrared detection has been shown to be very appropriate for high temperature analysis of polyolefins. After some early reports in which dispersive or single-band filter-based detectors were applied, Fourier transform detectors have been described for this application, in order to improve the method sensitivity. Modern simple filter-based detectors prove, however, comparable sensitivity while providing a number of practical advantages when coupled to chromatographic systems: reduced cell volume, simplified hardware, continuous generation of absorbance chromatograms, as well as simpler data collection and processing. A practical method for calibration, using multiple-band signals obtained with filter-based detectors and a small number of reference materials, is here discussed. Calibration data are used to compare the performance of detectors based on different opto-electronic technologies and filter designs. A procedure for estimation of errors in the slice-by-slice measured methyl frequency, based on signal-to-noise ratio considerations, is described. The good accuracy provided by the filter-based IR detectors was noticeable, considering that it was obtained using a small set of reference materials. A minimal concentration of 0.009. mg/mL was estimated to be required at the detector cell, in order to keep the errors below one unit of methyl per one thousand total carbons. This low minimal concentration requirement allows using standard SEC conditions, without compromising the molar mass distribution accuracy and resolution. © 2012 Elsevier B.V.


Frijns-Bruls T.,Royal DSM | Ortin A.,Polymer Char | Weusten J.,Royal DSM | Gelade E.,Royal DSM
Macromolecular Symposia | Year: 2015

Summary Even though polyolefins are simple polymers from a chemical structure point of view, their full characterization in practice is still an intriguing task. Basic macromolecular characteristics of polyethylene or polypropylene like molar mass moments and their distributions (MMD) but also chain conformation and thus information on long-chain branching, can be addressed with high-temperature size-exclusion chromatography (HT-SEC). Hyphenation of infrared detection to size-exclusion chromatography expands possibilities of SEC even more and allows to reveal comonomer incorporation across molecular weight and thus generate a fingerprint of a given catalytic system used in polyolefin synthesis. Multiband filter-based infrared detector gives an easy and fast access to so-called short chain branching distribution (SCB) vs MMD by coupling to HT-SEC. In this work, we summarize recent findings on application of a filter-based IR detector (IR5-MCT) towards characterization of polyolefins synthesized with different catalytic systems and varying comonomer types. It is found that for copolymers of polyethylene with 1-butene, 1-hexene or 1-octene (non-C3), one linear calibration line can be used in the range up to 70 CH3/1000TC, thus covering the range necessary for common applications like for instance HDPE or LLDPE. For ethylene-propylene copolymers (C3), over the broad range up to 333 CH3/1000TC, the calibration line is best fitted to a second order polynomial. C3 copolymers show a different behavior compared to non-C3 copolymers, irrespective the amount of comonomer incorporated in the polymer. We show that mixtures of PP and PE homopolymers result in equivalent response as the copolymers of the same average composition and thus can also be used to set up calibration lines. Based on this evaluation practical aspects of IR5-MCT calibration are discussed. © 2015 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim.


Honghong H.,Sinopec | Meifang G.,Sinopec | Juan L.,Sinopec | Ortin A.,Polymer Char | Yau W.W.,Polymer Characterization Consultant United States
Macromolecular Symposia | Year: 2015

Summary The use of High Temperature Gel Permeation Chromatography (HT-GPC) with online infrared (IR) detector to analyze copolymer composition of propylene-1-butene (P-B) copolymer is investigated in this study. This technique is based on the measurement of the methyl to methylene ratio by an online infrared detector. This measurement is made possible by the highly discriminating power of a modern multiple band filter-based IR detector (IR5 MCT) to detect the P-B copolymer chemical structure. Also discussed is an alternative method, based on the application of the triple-detector GPC (GPC with IR, viscometer and light scattering coupled detectors) approach and Mark-Houwink plot. © 2015 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim.


Monrabal B.,Polymer Char
Advances in Polymer Science | Year: 2013

New polyolefin resins, in spite of their simple chemistry, just carbon and hydrogen atoms, have become by design complex polymers with improved performance for the desired application. Besides the fundamental molar mass distribution, there are many other features that can be controlled when dealing with copolymers and new multireactor/multicatalyst resins. The average properties measured by spectroscopic techniques are not enough to define the microstructure of the new resins; it is necessary to fractionate the polymer according to certain parameters such as molar mass, branching, or stereoregularity. Separation techniques have become essential for the control and characterization of these polymers; nevertheless, full characterization is not a simple task and has demanded the development of new separation methodologies in recent years, and in many cases multiple separation techniques are required to define the microstructure. A review of the most important separation techniques with emphasis on the new technologies is given and the applications of these new polyolefin resins discussed. © Springer-Verlag Berlin Heidelberg 2013.


Monrabal B.,Polymer Char | Romero L.,Polymer Char
Macromolecular Chemistry and Physics | Year: 2014

The fractionation of industrial polypropylene resins by crystallization or adsorption is a challenging task due to the existence of stereoregularity and the fact that homopolymer and propylene-rich copolymers are semicrystalline, as is the case with polyethylene homopolymer, which is usually present in complex polypropylene resins. The separation mechanisms involved in crystallization and adsorption techniques are investigated. Crystallization techniques and adsorption chromatography on graphitized carbon using a temperature gradient separate the full range of propylene ethylene copolymers following a U-shaped curve and cannot provide unequivocal compositional results. The addition of an infrared detector to measure the level of branches at each elution temperature provides a new dimension that better defines the separated components. A step further in separation is using cross-fractionation chromatography (composition followed by molar-mass separation), which makes use of all the mechanisms investigated to provide the most-extended separation of complex high-impact polypropylene resins. (Graph Presented). © 2014 Wiley-VCH Verlag GmbH & Co.


Monrabal B.,Polymer Char | Lopez E.,Polymer Char | Romero L.,Polymer Char
Macromolecular Symposia | Year: 2013

Summary Since the introduction of high temperature interaction chromatography for the analysis of polyolefins the technique has demanded a particular interest in the analysis of elastomers where crystallization techniques will meet a limitation given the low crystallinity of these polymers. In this paper the introduction of non carbon adsorption supports such as molybdenum sulfide, boron nitride and tungsten sulfide with equivalent separation to graphitized carbon packing in TGIC analysis of polyolefins is presented. A mechanism for the separation of polyolefins by adsorption chromatography on layered substrates is proposed. The influence of solvent polarity in interaction chromatography is discussed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Monrabal B.,Polymer ChAR
International Polyolefins Conference 2010: Finding Value in Today's Business Environment | Year: 2010

The introduction of single site catalysts in the polyolefins industry has opened new possibilities in polymer design through multiple reactor-catalyst systems. The obtained microstructures, very often bimodal or trimodal in terms of composition are quite difficult to characterize and a multidisciplinary approach must be followed. In terms of Molar mass distributions, GPC with multiple detectors and Asymmetric Flow FFF for very high Mw resins are being used. In terms of composition distribution TREF, CRYSTAF, CEF and new adsorption HPLC are the techniques of choice. A brief review of the techniques will be presented as an introduction to the full analysis of the Bivariate Distribution by Cross Fractionation Chromatography with latest examples.


Summary The separation of polyolefin copolymers in terms of composition has been typically performed by crystallization techniques. In the last years, a new liquid chromatography approach has become available that extends the range of composition analysis applicable towards higher comonomer content. Every technique has its capabilities and limitations, and the use of multiple hyphenated techniques is often required to provide unequivocal results for characterizing the microstructure of complex copolymers like high impact polypropylene. A good understanding of the individual separation mechanisms is essential to interpreting the obtained results properly, and this becomes a challenging task when dealing with ethylene-propylene copolymers or homopolymer blends. The separation of these resins by the existing techniques is discussed. The role of solvent and the adsorbent in the separation mechanisms is investigated and a comparison of crystallization and liquid adsorption chromatography with various types of adsorbents is presented. © 2015 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim.


Infrared detection has been shown to be very appropriate for high temperature analysis of polyolefins. After some early reports in which dispersive or single-band filter-based detectors were applied, Fourier transform detectors have been described for this application, in order to improve the method sensitivity. Modern simple filter-based detectors prove, however, comparable sensitivity while providing a number of practical advantages when coupled to chromatographic systems: reduced cell volume, simplified hardware, continuous generation of absorbance chromatograms, as well as simpler data collection and processing. A practical method for calibration, using multiple-band signals obtained with filter-based detectors and a small number of reference materials, is here discussed. Calibration data are used to compare the performance of detectors based on different opto-electronic technologies and filter designs. A procedure for estimation of errors in the slice-by-slice measured methyl frequency, based on signal-to-noise ratio considerations, is described. The good accuracy provided by the filter-based IR detectors was noticeable, considering that it was obtained using a small set of reference materials. A minimal concentration of 0.009 mg/mL was estimated to be required at the detector cell, in order to keep the errors below one unit of methyl per one thousand total carbons. This low minimal concentration requirement allows using standard SEC conditions, without compromising the molar mass distribution accuracy and resolution.

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