Crystallization analysis fractionation

Anantawaraskul, S., Soares,. B. P. and Wood-Adams, P. M. Fractionation of Semicrystalline Polymers by Crystallization Analysis Fractionation and Temperature Rising Elution Fractionation. Vol. 182, pp. 1-54. 

Rytter et al. reported polymerizations with the dual precatalyst system 14/15 in presence of MAO [30]. Under ethylene-hexene copolymerization conditions, 14/MAO produced a polymer with 0.7 mol% hexene, while the 15/MAO gave a copolymer with ca. 5 mol% hexene. In the mixed catalyst system, the activity and comonomer incorporation were approximate averages of what would be expected for the two catalysts. Using crystallization analysis fractionation (CRYSTAF) and differential scanning calorimetry (DSC) analysis, it was concluded in a later paper by Rytter that the material was a blend containing no block copolymer [31],... 

The effect of both crystallization and branching was studied for 19 different PE types produced by different polymerization processes and catalyst types, which were characterized by the so-called crystallization analysis fractionation. The solubility of PE fractions in trichlorobenzene (TCB) refers to their ability to create tie molecules and therefore correlates with ESCR, which was measured with the standard bent-strip method in Igepal CO-630 [84], The fractions were distinguished by their solubility in different temperature ranges, where the solubility depends on either crystallinity and branching ... 

Polymers by Crystallization Analysis Fractionation and Temperature Rising Elution... 

Crystallization analysis fractionation (CRYSTAF) was developed by Monrabal [99] in 1991 as a process to speed up the analysis of the CCD, which at that time lasted around 1 week per sample with the TREF technique. CRYSTAF shares with TREF the same principle of separation according to crystallizability. In CRYSTAF, the samples are not crystallized in a column but in a stirred vessel with no support, and only a temperature cycle (crystallization) is required [64], thus speeding up the analysis process and simplifying the hardware requirements. 

Monrabal B (2000) Temperature rising elution Iractionation and crystallization analysis fractionation. In Meyers RA (ed) Encyclopedia of analytical chemistry. Wiley, Chichester, pp 8074-8094... 

Methods based on differences in crystallizability of macromolecules - temperature rising elution fractionation, TREF and crystallization analysis fractionation, CRYSTAF. 

The company Polymer Char (Valencia, Spain) was created for developing fully automated PO characterization instruments. The first device, commerciahzed and patented in 1994, was the CRYSTAF, crystallization analysis fractionation, for the fast measurement of the chemical composition distribution (CCD) in PE, PP, copolymers, and blends. Next came the SEC (with a quadruple detector system) and then SEC/a-TREF and p-TREF instruments. The first commercial, fully automated cross-fractionating SEC/TREF apparatus for microstructure characterization of POs was described by Ortin et al. (2007). The instrument yields a bivariate distribution CCD by TREE fractionation and then SEC fraction analysis in a single run. A schematic diagram of this new cross-fractionation instrument is shown in Fig. 18.7. 

S. Anantawaraskul, J.B.P. Soares, M. Paula, P. Wood-Adams, Fractionation of semicrystalline polymers by crystallization analysis fractionation and temperature rising elution fractionation. Adv. Polym. Sci. 182, 1-54 (2005)... 

B. Monrabal, Crystallization analysis fractionation a new technique for the analysis of branching distribution in polyolefins. J. Appl. Polym. Sci. 52(4), 491-499 (1994)... 

B. Monrabal, Temperature rising elution Ifactionation and crystallization analysis fractionation, in Encyclopedia of Analytical Chemistry, ed. by B. Moiuubal, R.A. Meyers (Wiley, New York, 2000) B. Monrabal, Method for separating and purifying crystallisable organic compounds, U.S. Patent 8071714 of 06 Dec 2011, priority 15 Mar 2006, to Polymer Characterization, S.A. 

B. Monrabal, P. del Hierro, Characterization of polypropylene-polyethylene blends by temperature rising elution and crystallization analysis fractionation. Anal. Bioanal. Chem. 399, 1557-1561 (2011)... 

Crystallization analysis fractionation (Crystaf) fractionates polymer chains according to differences in crystallizability. Crystaf can be used to fractionate polymers due to differences in chemical composition, comonomer sequence length, and tacticity. It may also respond to long-chain branching, provided that the polymer is branched enough to affect its crystallinity. The fractionation principle operative in Crystaf was discussed in the section on batch fractionation for the case of slowly cooling (or warming) solutions of semicrystalline polymers. 

In principle, SEC can be calibrated with standards of narrow molecular weight distribution of the polymer that one wishes to analyze. In this way, a calibration curve relating molecular weight to elution volume is obtained, in a fashion similar to what is done for the calibration of TREF or crystallization analysis fractionation. This approach, however, suffers from the limitation that the calibration curve is only applicable to one specific polymer. Additionally, narrow standards are not available for many different types of polymers. In principle, the batch fractionation techniques discussed above could be used to obtain such narrow standards, but these processes are time-consuming and, as explained, do not permit the isolation of samples with very narrow molecular weight distributions. 

Fig.l Cumulative and differential crystallization analysis fractionation (Crystaf) profiles of a blend of two polyolefins... 

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