Polyolefins, analysis functionalized

Abstract The synthesis and characterization of polyolefins continues to be one of the most important areas for academic and industrial research. One consequence of the development of new tailor-made polyolefins is the need for new and improved analytical techniques for the analysis of polyolefins with respect to molar mass, molecular topology and chemical composition distribution. This review presents different new and relevant techniques for polyolefin analysis. The analysis of copolymers by combining high-temperature SEC and FTIR spectroscopy yields information on chemical composition and molecular topology as a function of molar mass. Crystallization based fractionation techniques are powerful methods for the analysis of short-chain branching in LLDPE and the analysis of polyolefin blends. These methods include temperature-rising elution fractionation, crystallization analysis fractionation and the recently developed crystaUization-elution fractionation. 

To summarize, all techniques used for polyolefin characterization have advantages and disadvantages. Some information can be obtained more reliably from one technique and some other fi om other techniques. One really has to decide on the problems to be addressed using a given technique. Nevertheless, 2D-HT-HPLC seems to be one major technique to be used for polyolefin analysis in the future due to its ability to provide MMD as a function of CCD of the sample which is not possible by other approaches. 

Infrared measurement of additive concentrations is a more complex analysis than initially expected, as some additives may undergo a variety of chemical reactions during processing, as shown by Reeder et al. [128] for the FTIR analysis of phosphites in polyolefins. Some further examples of IR work refer to PVC/metal stearates [129], and PE/Santonox R [68,130]. Klingbeil [131] has examined the decomposition of various organic peroxyesters (TBPB, TBPP, TBPA and TBPO) and a peroxidicarbonate (BOPD) as a function of pressure, temperature and solvent by means of quantitative FTIR using an optical high p, T reaction cell. 

The application of refractive index and differential viscometer detection in SEC has been discussed by a number of authors [66-68]. Lew et al. presented the quantitative analysis of polyolefins by high-temperature SEC and dual refractive index-viscosity detection [69]. They applied a systematic approach for multidetector operation, assessed the effect of branching on the SEC calibration curve, and used a signal averaging procedure to better define intrinsic viscosity as a function of retention volume. The combination of SEC with refractive index, UV, and viscosity detectors was used to determine molar mass and functionality of polytetrahydrofuran simultaneously [70]. Long chain branching in EPDM copolymers by SEC-viscometry was analyzed by Chiantore et al. [71]. 

The simultaneous analysis of concentration and composition in GPC measurements is of significant interest for today s complex polyolefin copolymers. The same IR detector can be used to analyze ethylene-vinyl acetate (EVA) or other functional polyolefin copolymers (with a carbonyl group) as a function of molar mass. All that is needed is to replace the methyl interference filter by a carbonyl region filter. An example of a maleic anhydride-modified PE is shown in Fig. 9, with an IR interference filter measuring at 1,740 cm . ... 

Although clearly less routine that x-ray diffraction, PDF analysis of conventional polymers has been used, perhaps most notably, in the study of polyolefins [403,404] and polyethylene oxides [405-407]. This PDF approach has also been utilized in structural analysis of PANis [408-413], functionalized polysilanes [356,414], and PPys [290]. An early PDF PANi EB study by Laridjani et al. [410] resolved differences in the local structure of type I and type II samples. Modeling is often used in conjunction... 

For a detailed analysis of olefin copolymers or polyolefin blends it is important to determine the CCD in addition to the MMD. The bulk chemical composition of polyolefins can be determined quantitatively by FTIR or NMR spectroscopy. Dual information on the chemical composition as a function of molar mass can be obtained when HT-SEC is directly coupled to these spectroscopic methods. Interfacing SEC with H-NMR is a cost-intensive option for the understanding of molecular structure as a function of separation. It has, however, the advantage... 

Since it is a less laborious technique than GPC or NMR, MALDI-TOF has attracted interest as a possible technique for characterizing commercial polymers such as polyethylene. However, polyolefins cannot be analyzed using MALDI-TOF, since they lack a functional group that can be cationized. Bauer et al. [88] proposed a technique for overcoming this problem in the case of polyethylene by the chemical modification of the polymer prior to analysis. 

These effects, supported by a marked increase of melt viscosity, were related to the occurrence of chemical interactions between the polyamides and functionalized polyolefins at the interface. DSC analysis showed that incompatible Ny6/PP and Ny6/LDPE blends exhibit at all compositions separated crystallization peaks of the two components, whereas the compatibilized blends displayed fractionated and/or coincident crystallization phenomena. For Ny6/PP-AA blends where Ny6 is the matrix, the crystallization of the polyamide phase takes place in a narrow range, close to 190 C, as observed for pure Ny6 (Hg. 10.26a). When Ny6 is the dispersed phase. 

A brief review is presented on techniques for the analysis of polyolefins and additives in polyolefins. Techniques considered include high-temperature GPC combined with FTIR spectroscopy for the analysis of chemical composition as a function of molar mass, crystallisation fiactionation for the analysis of short-chain branching in LLDPE and of polyolefin blends and pyrolysis-gas chromatography-mass spectrometry for the determination of additives, such as antioxidants, in polyolefins. 13 refs. (3rd Annual UNESCO School lUPAC Conference on Macromolecules and Materials Science, Stellenbosch, South Africa, 2000)... 

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