Rubbery materials characterisation

Characterise Chemically Modified Rubbers and Rubbery Materials... 

Since infrared (IR) spectroscopy is one of the most widely used techniques for the identification of materials at the molecular level, it has been extensively used to characterise the rubbery materials. In this chapter the rubbery materials encompass PE, plasticised PVC, thermoplastic elastomers and ionomers. 

Different types of interaction in rubbery materials, which include PE, plasticised PVC, TPE, ionomeric polyblends, and blends of plastics and rubbers can be characterised by different types of IR spectroscopic techniques. 

Characterisation of Chemical and Physical Networks in Rubbery Materials Using Proton NMR Magnetisation Relaxation... 

The use of solid-state NMR magnetisation relaxation experiments to characterise network structures in various rubbery materials is reviewed in this chapter. Comprehensive reviews of high-resolution NMR techniques can be found elsewhere [21-23, 30-35]. 

Quality tests are usually performed using bench-top, low filed NMR spectrometers. Volume-average properties are determined with this equipment. Surface layer of samples can be analysed using recently developed NMR-MOUSE (mobile universal surface explorer) [26, 188]. The NMR-MOUSE is a relatively small NMR device suited for the investigation of surface-near volume elements. Lateral surface heterogeneity of elastomeric materials can be scanned with this device. Possible applications of the NMR-MOUSE for the characterisation of rubbery materials were demonstrated [26,189-191]. 

Functional properties and stability of rubbery materials Chapters 1, 3, 4, 7, 12 and 13, give examples of applications of spectroscopic techniques for the characterisation of thermal stability and degradation, kinetics of thermal decomposition, ageing, oxidation and weathering, self-diffusion of small molecules in rubbery materials, adhesion of rubbers to metals, fluid adsorption and swelling. 

The crosslinking kinetics and the final state of cure are commonly studied with the aid of rheometers. NMR relaxation experiments can offer several advantages for the characterisation of the crosslinking kinetics in complex materials because of high method selectivity with respect to the rubbery chains/phases in polymer blends, filled and oil extended rubbers. 

Those which do crystallise invariably do not form perfectly crystalline materials but instead are semi-crystalline with both crystalline and amorphous regions. The crystalline phases of such polymers are characterised by their melting temperature (TJ. Many thermoplastics are, however, completely amorphous and incapable of crystallisation, even upon annealing. Amorphous polymers (and amorphous phases of semi-crystalline polymers) are characterised by their glass transition temperature (T), the temperature at which they transform abruptly from the glassy state (hard) to the rubbery state (soft). This transition corresponds to the onset of chain motion below T the polymer chains are unable to move and are frozen in position. Both T and T increase with increasing chain stiffness and increasing forces of intermolecular attraction. 

From the point of view of the valnes of the two moduli, the same regions as described above are observed, depending on the temperature. In the first temperature interval, between 0 and 25 °C, the transition from the glassy (G" > G ) to rubbery (G > G") region can be observed. In the second area, at temperatures between 50 and 100 °C, the elastic properties of the material dominate over the viscous properties (G > G"). In this area, the mechanical behavionr is characterised by a plateau region in the development of the elastic moduli with frequency. Finally, in the third zone, at temperatures near 125 °C, the sample is in the terminal region of the mechanical spectrum (G" > G ), but with slopes lower than 1 and 2 for the viscous and elastic moduli respectively. 

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