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Valencia, Spain

Monrabal B.,Polymer Char
Advances in Polymer Science

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. Source

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

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. Source

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

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. Source

Honghong H.,Sinopec | Meifang G.,Sinopec | Juan L.,Sinopec | Ortin A.,Polymer Char
Macromolecular Symposia

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. Source

Liberman S.,Federal University of Rio Grande do Sul | De Azeredo A.P.,Braskem S.A. | Dos Santos F.P.,Braskem S.A. | Da Silva M.A.,Braskem S.A. | And 2 more authors.
Macromolecular Symposia

Summary Heterophasic poly(propylene) copolymers obtained by sequential polymerization are multi-component products formed by a crystalline matrix of poly(propylene) and an ethylene-propylene rubber phase. Some crystalline polyethylene and poly(ethylene-co-propylene) are formed in the rubber synthesis step by copolymerization of ethylene and propylene. These multi-component systems present a complicated microstructure and heterophasic morphology. In this study, two heterophasic copolymers with the same total amount of rubber but different composition and molecular weight, were thoroughly analyzed. The morphology was evaluated by SEM and AFM techniques. The complexity of the system required some attention in the fractionation methodology to perform an accurate interpretation of results and different methodologies of fractionation, especially for obtaining PE fractions as free of PP as possible, were performed in order to better characterize the crystalline polyethylene fractions in the copolymers. Preparative TREF was used to obtain fractions for further analysis by 13C-NMR, DSC and GPC. Also samples were submitted to Cross Fractionation Chromatography (CFC). Results obtained by the different methodologies were compared. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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