Characterisation, polymer

DTA has been used to characterise polymers at temperatures up to 150 °C. Under a reactive gas (oxygen) or an inert gas (nitrogen) plots of the applied temperature versus the temperature of specimens (or calories per second) detect positive (i.e., exothermic) or negative (i.e., endothermic) temperature changes (i.e., AH) in the reactions or phase changes occurring upon heating the polymer. 

DSC has been used in characterisation studies on phenol formaldehyde resins [9], polyimides [24, 25] and macrocyclic(arylene multisulfides) [26]. 

Hatada and T. Kitayama, NMR Spectroscopy of Polymers, Springer-Verlag, Berlin (2004). 

Litvinov and P.P. De (eds.). Spectroscopy of Rubbers and Rubbery Materials, Rapra Technology Ltd., Shawbury (2002). 

A Practical Guide to Understanding the NMR of Polymers, Wiley-Interscience, New York, NY (2002). 

The common anionic, non-ionic and cationic monomers can be readily polymerised to very high molecular weight, such that they routinely exceed the upper molecular limits of well-established techniques such as size exclusion chromatography (SEC). Estimates based on empirical methods such as intrinsic viscosity determination, indicate that polymer chains with 100,000 units and more can be expected during routine synthesis of such polymers. This corresponds to the polymer chain having a molecular weight around 10 million or more. 

When prepared as a dilute solution in water, the polymer dissolves and forms an interpenetrating network of polymer chains which are independently mobile. This network is reflected in a substantial increase in viscosity over that of water and is responsible for the rheological properties of the polymer solutions. 

There are four main application areas for this technique, namely polymer characterisation and determination of extractables, migrants and additives. 

Kawai and co-workers [5] determined the composition of butyl acrylate-ethyl acrylate copolymers with a narrow chemical composition distribution by H-NMR spectroscopy and the components of the copolymers separated by normal and reversed phase high-performance liquid chromatography using crosslinked acrylamide and styrene beads. Samples containing higher butyl acrylate content eluted faster with normal phase HPLC while the opposite occurred with reversed phase HPLC, indicating that butyl acrylate is less polar than ethyl acrylate. 

Obata and co-workers [7] separated stereoisomeric products formed during the synthesis of (2S, 3S)-2,3 bntane diyl (2S, 4S) 2, 4 pentane diyl and (2S, 5S) hexane diyl bis (4-vinyl benzoate) by chiral HPLC and characterised these polymers by high resolution field desorption mass spectroscopy (HR-FD-MS) and C-NMR. 

The chemical structures of the highly branched living linked polystyryl anion using 4 chloro dimethylsilyl styrene (CDMSS) end-capped polystyrene is depicted below  

Masci and co-workers [9] characterised block copolymers of N-isopropyl acrylamide with dimethyl acrylamide or 3-sulfopropyl methacrylate by HPLC, gel permeation chromatography (GPC) and MALDI-ToF-MS. Data are provided on the reaction conditions, kinetic data, M and polydispersities for the polymers and copolymers. 

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P. W. AHen, Technique of Polymers Characterisation, Butterworths, London, 1959 Dilute Solution Properties of Acrylic andMethacylic Polymers, SP-160, Rohm and Haas Co., Philadelphia, Pa. 

P. W. Aden, Technique of Polymer Characterisation, Butterworths Scientific PubHcations, London, 1959. 

J. P. Ibar and co-workers, in Polymer Characterisation Physical Property, Spectroscopic, and Chromatographic Methods, American Chemical Society, Washington, D.C., 1990, p. 167. 

J. K. Gillham, Developments in Polymer Characterisation-3, AppHed Science Pubhshers, London, 1982, chapt. 5. 

In order to understand polymer solution behaviour, the samples have to be characterised with respect to their molecular configuration, their molar mass and polydispersity, the polymer concentration and the shear rate. Classical techniques of polymer characterisation (light scattering, viscometry, ultracentrifugation, etc.) yield information on the solution structure and conformation of single macromolecules, as well as on the thermodynamic interactions with the solvent. In technical concentrations the behaviour of the dissolved polymer is more complicated because additional intramolecular and intermolecular interactions between polymer segments appear. 

R. A. Pethrick and J.V. Dawkins (eds), Modern Techniques for Polymer Characterisation, John Wiley Sons, Ltd, Chichester (1999). 

Y. Bourgeois, in Polymer Characterisation 2002, Rapra Technology Ltd, Shawbury (2000). 

Applications The majority of SFE applications involves the extraction of dry solid matrices. Supercritical fluid extraction has demonstrated great utility for the extraction of organic analytes from a wide variety of solid matrices. The combination of fast extractions and easy solvent evaporation has resulted in numerous applications for SFE. Important areas of analytical SFE are environmental analysis (41 %), food analysis (38 %) and polymer characterisation (11%) [292], Determination of additives in polymers is considered attractive by SFE because (i) the SCF can more quickly permeate throughout the polymer matrix compared to conventional solvents, resulting in a rapid extraction (ii) the polymer matrix is (generally) not soluble in SCFs, so that polymer dissolution and subsequent precipitation are not necessary and (iii) organic solvents are not required, or are used only in very small quantities, reducing preparation time and disposal costs [359]. 

Table 4.45 shows the main features of SEC. This technique has become an indispensable tool for polymer characterisation. SEC has some advantages over other LC methods, such as the predictability of the end of a chromatographic run and of the retention times in a calibrated chromatographic system. SEC is an attractive technique for prefractionation or sample clean-up prior to a more sensitive RPLC technique. This intermediate step is especially interesting for experimental purposes whenever polymer matrix interference cannot be separated from the peak of interest [647]. Disadvantages are that the whole separation must be eluted within the... 

B.J. Hunt and M.I. James (Eds.), Polymer Characterisation, Blackie Academic Professional, Glasgow, 1993. 

That particular combination of properties possessed by high polymers, characterising the rubber-like state. Depending on the temperature and the time of stressing, a high polymer may show viscous flow or high elasticity. See Elasticity, Glass Transition, Thixotropy and Viscosity. 

W.T. Ford, T. Balakrishnan, in Polymer Characterisation, Advances in Chemistry Series, Vol. 203, ed. C.D. Craver, Amer. 

Foams 2000 Second International Conference on Thermoplastic Foam. Conference proceedings. Parsippany, N.J., 24th-25th October 2000, p. 139-48 USING POLYMER CHARACTERISATION TECHNIQUES TO PREDICT LDPE RESIN SUITABILITY FOR EXTRUDED FOAM APPLICATIONS Anger J Ngnyen L Nova Chemicals Corp. 

Solvatochromic probes have found applications in polymer characterisation, where they can be used to look for localised polar features at the molecular level. Two distinct approaches can be adopted ... 

The objectives of this paper are to discuss and present some examples of how polymer characterisation must be used in order to determine a range of important polymeric properties in recycled plastics. These properties in turn are used to define the quality of recycled plastics. 

Polymer Characterisation for Quality Assessment of Commingled and Separated Recycled Polyethylenes... 

Thermal analysis is a group of techniques in which a physical property of a substance is measured as a function of temperature when the sample is subjected to a controlled temperature program. Single techniques, such as thermogravimetry (TG), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), dielectric thermal analysis, etc., provide important information on the thermal behaviour of materials. However, for polymer characterisation, for instance in case of degradation, further analysis is required, particularly because all of the techniques listed above mainly describe materials only from a physical point of view. A hyphenated thermal analyser is a powerful tool to yield the much-needed additional chemical information. In this paper we will concentrate on simultaneous thermogravimetric techniques. 

Reprinted with permission from Developments in Polymer Characterisation, Ed., J. V. Dawkins, Applied Science Publishers, London, 1983, Chapter 3,119. Copyright J.V. Dawkins, 1983... 

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