Polymer blends transmission electron

Microstructures of (1) PE-g-PPG polymer hybrid and (2) the blended sample of PE and PPG were observed by transmission electron microscopy (TEM) images after the preparation of press sheets of each polymer sample at 200 °C. The TEM images of the resulting polymer hybrid reveal the nanometer level microphase-separation morphology between the PE segment and the PPG segment compared with the PE/PPG blended polymer. From the result, the nanodispersion of different segments in polymer hybrids is possible, but different from the blended polymer sample (Fig. 8). 

Samples for the viscoelastic experiments were prepared by a conventional slow-solvent-evaporation technique (1) followed by vacuum drying. For ease in handling in certain experiments, some samples were lightly cured using a 30-MRad dose of electrons other experiments were carried out on uncured materials. Transmission electron microscopy (Phillips Model 200) was used to investigate possible morphological features in the block polymers and blends. Details of the various staining techniques used are presented elsewhere (1,11,12,13). 

FIGURE 19.7 Transmission electron micrographs of the obtained fiber after treatment at 1773 K. (From Narisawa, M. et al., SiC ceramic fibers synthesized from polycarbo-silane-polymethylsilane polymer blends, Ceram. Trans., 144A, 173, 2002. Reprinted with permission of The American Ceramic Society, www.ceramics.org.)... 

These polymers can be blended either in solutions or in the melt. A blend of up to 2% of polymer 3 with polystyrene appeared clear, but turbid blends resulted from higher percentages of polymer 3. The Tg s of blended polymers containing up to 30% of polymer 3 did not change from that of pure polystyrene. Transmission electron microscope (TEM) analysis of the 5% blend showed that there are bimodal distributions of polymer 3 domains, a small amount of approximately 10 nm domains, and a large portion of approximately 1 l domains. 

Blending of polyacetylene with polybutadiene provides an avenue for property enhancement as well as new approaches to structural studies. As the composition of the polyacetylene component is increased, an interpenetrating network of the polymer in the polybutadiene matrix evolves from a particulate distribution. The mechanical and electrical properties of these blends are very sensitive to the composition and the nature of the microstructure. The microstructure and the resulting electrical properties can be further influenced by stress induced ordering subsequent to doping. This effect is most dramatic for blends of intermediate composition. The properties of the blend both prior and subsequent to stretching are explained in terms of a proposed structural model. Direct evidence for this model has been provided in this paper based upon scanning and transmission electron microscopy. 

Scanning electron microscopy (SEM) data for carbon-black compounds and conductive polymer blends [72c], supported by recent transmission electron microscopy (TEM) evaluations [79,80] (shown in Figure 11.39) were made, they also contradict the assumption of a statistical distribution. We find complete dispersion below the critical volume concentration (I) and a sudden stiucture formation ( branched flocculate chains ) at the critical volume concentration. This structural feature remains at higher concentrations. 

Botana et al. [50] have prepared polymer nanocomposites, based on a bacterial biodegradable thermoplastic polyester, PHB and two commercial montmorillonites [MMT], unmodified and modified by melt-blending technique at 165°C. PHB/Na and PHB/ C30B were characterized by differential scanning calorimetry [DSC], polarized optical microscopy [POM], X-ray diffraction [XRD], transmission electron microscopy [TEM], mechanical properties, and burning behavior. Intercalation/exfoliation observed by TEM and XRD was more pronounced for PHB30B than PHB/Na,... 

In practice, polymer blends are often produced by mechanical mixing in the melt. Most of the blend combinations are immiscible and the product is demixed but often in very small dimensions so that often scanning or transmission electron microscopy (SEM, TEM) have to be used to analyse the morphology in detail. 

The SEM is also used to do X-ray/elemental analysis. This technique is qualitative. X-ray analysis and mapping of the particular elements present is useful for the identification of inorganic fillers and their dispersion in compounds as well as inorganic impurities in gels or on surfaces and curatives, e.g., aluminum, silicon, or sulfur in rubber compounds and Cl and Br in halobutyl blends. Refer to Transmission Electron Microscopy. (Source Cheremisinoff, N.P. Polymer Characterization Laboratory Techniques and Analysis, Noyes Publishers, New Jersey, 1996). 

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