Thermoplastic elastomers spectroscopy

The ionic aggregates present in an ionomer act as physical crosslinks and drastically change the polymer properties. The blending of two ionomers enhances the compatibility via ion-ion interaction. The compatibilisation of polymer blends by specific ion-dipole and ion-ion interactions has recently received wide attention [93-96]. FT-IR spectroscopy is a powerful technique for investigating such specific interactions [97-99] in an ionic blend made from the acid form of sulfonated polystyrene and poly[(ethyl acrylate - CO (4, vinyl pyridine)]. Datta and co-workers [98] characterised blends of zinc oxide-neutralised maleated EPDM (m-EPDM) and zinc salt of an ethylene-methacrylic acid copolymer (Zn-EMA), wherein Zn-EMA content does not exceed 50% by weight. The blend behaves as an ionic thermoplastic elastomer (ITPE). Blends (Z0, Z5 and Z10) were prepared according to the following formulations [98] ... 

IR spectroscopy can be used to characterise not only different rubbers, but also to understand the structural changes due to the chemical modification of the rubbers. The chemical methods normally used to modify rubbers include hydrogenation, halogenation, hydrosilylation, phosphonylation and sulfonation. The effects of oxidation, weathering and radiation on the polymer structure can be studied with the help of infrared spectroscopy. Formation of ionic polymers and ionomeric polyblends behaving as thermoplastic elastomers can be followed by this method. Infrared spectroscopy in conjunction with other techniques is an important tool to characterise polymeric 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. 

The physical interactions in TPE can be characterised by IR spectroscopy. A few examples of such studies are discussed here. Examples of PE based thermoplastic elastomers are NR/PE blends [50, 52]. TPE [49] based on 50/50 NR/LDPE, forms co-continuous morphological structure of both NR and LDPE. Thermal analysis shows that the blend is immiscible and from IR spectra of the 50/50 NR/LDPE blends [53], it is observed, the peaks of NR and PE exist almost in the same positions in the blend with a very little shift (Figure 5.12). The absorption band at 833 cm"1 for cis >C = C in NR (Figure 5.12) is shifted to 836 cm 1. Similarly the peak at 1370 cm"1 (C-H stretching of CH3 group) shifts to 1373 cm"1, while the peak for C=C double bond shifts from 1660 cm"1 to 1658 cm"1, and the band at 1467 cm"1 for -CH2 in LDPE (Figure 5.12) is shifted to 1462 cm 1. The spectra thus confirm that there exist only physical interactions in NR-PE blend. 

Trimethylol propane triacrylate Trimethylol propane trimethacrylate Tetramethyl thiuram disulphide Total correlation spectroscopy Time-of-flight MS Thermoplastic elastomer(s)... 

Segmented thermoplastic elastomers exhibit structural heterogeneity on the molecular, the domain, and in some cases on a larger scale involving periodic or spherulitic texture. Each level of structural organization is studied by specific methods. Molecular sequence distributions can be studied by chemical methods, such as NMR or IR spectroscopy. 

J. Kehn, Forschungsbericht 213. High Resolution NMR Spectroscopy for the Determination of Elastomers, Blends and Thermoplastic Elastomers — Carbon and Proton NMR Spectra Catalogue, BAM, Berlin (1995). 

Apart from phase discrimination (hard V5-. soft contents of materials), reports of chemical composition analysis by low-field H NMR spectroscopy are increasing. LR-NMR allows analysis of the soft-block content of (co)polymer blends in the solid state, as e.g. in polyesterethers and other thermoplastic elastomers. LR-NMR can also be applied... 

Dardin A, Boeffel Ch, Spiess H-W and Stadler R (1994) Orienration behavior of thermoplastic elastomers studied by 2H-NMR and FT-IR spectroscopy, Polym Mater Sci Eng 71 248-249. 

Dielectric spectroscopy of poly(ether ester) thermoplastic elastomers... 

Dielectric spectroscopy was shown to be a powerful technique when dealing with molecular dynamics in thermoplastic elastomers. The combination of dielectric measurements over broad frequency and temperature ranges with a precise structural characterization opens up new possibilities of studying the structure-dynamic relationships in block copolymers (see also Chapter 14). 

The most reliable (time-consuming and costly) identification method is to use infrared spectroscopy measurements to determine the material. The Rapra Collection of Infrared Spectra of Rubbers, Plastics, and Thermoplastic Elastomers can be used to compare the spectrum of a test material to reference spectra. The transmission spectra in this reference are obtained either from cast or molded thin film or in the case of cross-linked materials by pyrolysis of the material in a Pyrex tube. 

For the majority of composites and their intended applications, the transfer of stress from the point of application throughout the remainder of the composite structure is by a shearing mechanism. The interface between fiber and matrix therefore, plays a major role. This paper examines the drawbacks from conventional micromechanical testing of model composites and introduces the benefits of fragmentation testing of aramid fibers in a thermoplastic elastomer matrix using Raman spectroscopy. Accurate and precise measurements of the interfacial shear strength between fibers and matrix are attainable. 

Hung Yu Chen, Application of high resolution NMR spectroscopy to elastomers in solution. Rubber Chem. Technol. 41, 47 (1968) (also contains data on thermoplasts, etc.). 

To understand this result we may consult the evidence concerning structural changes during deformation of similar materials, provided by in-situ mechano-cal-orimetry [294, 298], infra-red (IR) spectroscopy [51, 309], WAXS and SAXS [141, 284, 310]. Although the details differ with the precise chemical composition, some features seem to be common to thermoplastic PU elastomers. 

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