Polymer blends electron microscopy

D. A. Thomas, Morphology Characterization of Multiphase Polymers by Electron Microscopy, J. Polym. Sci. Polym. Symp. 60, 189 (1977). Morphology of polymer blends and IPNs. Electron microscopy techniques. 

A third disadvantage of studying polymers with electron microscopy is the radiation damage due to the electron beam. There are several primary and secondary irradiation effects, which can, on one side, damage the polymer, but on the other hand, contribute to a contrast enhancement, for example, if in polymer blends the thickness or the density in one part of the specimen is reduced by evaporation of volatile fractions of polymer chains, as in PVC/SAN blends (see Fig. 3.15) or if secondary cross-linking effects in semicrystalline polymers are stronger in the amorphous regions than in the crystalline ones, as in PEs [1,15,16]. 

Characterization and control of interfaces in the incompatible polymer blends were reported by Fayt et al. [23]. They used techniques such as electron microscopy, thermal transition analysis, and nonradiative energy transfer (NRET), etc. They have illustrated the exciting potentialities offered by diblock copolymers in high-performance polymer blends. 

Electron microscopy, 16 464, 487-495 history of, 16 487-488 in polymer blend morphology determination, 20 339-340 of PVC particles, 25 658-659 of silica, 22 371-372 in surface and interface imaging, 24 75-80... 

Microscopy. This is a powerful tool for studying visually the distribution of the two phases in the polyblend. One can tell not only the domain size of the dispersed phase but also which polymer forms the dispersed phase from refractive index. A phase contrast light microscope can detect heterogeneity at the 0.2-10 /x level. If the sample can be stained preferentially and sectioned with microtome, then under favorable conditions electron microscopy can show heterogeneity to a very fine scale. In a study of PVC-poly(butadiene-co-acrylonitrile) blend,... 

Tihe technological properties and the commercial application of several polymer blends have been studied extensively. Investigations of the basic principles, however, relating the phase structure of the blends to the properties of the individual components have not been carried out to an extent justified by the industrial value of these materials. Several methods have been used, the most successful being optical and electron microscopy and dynamic-mechanical measurements. Critical factors and difficulties in the morphological studies of polymer blends have been... 

Changing the milling temperature has a pronounced effect on the mechanical properties (19) and the physical state of the polymer blend (Table I). Figure 6 shows that the permeability and diffusion coefficients decrease considerably on increasing the milling temperature. This decrease can be correlated with the increased amount of very small PVC particles (< 0.2 /on) as observed by electron microscopy. The effect is... 

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). 

Binary blends (50/50 wt%) of different combinations of the polymers of Table III were prepared from benzene solution as described above. Either electron microscopy, measurements of dynamic mechanical properties, or both were used to ascertain the heterogeneity (or homogeneity ) of each blend. 

Interfacial agents, such as block copolymers, are known to reduce the Interfaclal tension and hence are expected to Increase the degree of dispersion in blends. The measurement of Interfacial tension for polymer systems is not easy. Most measurements have been made by the pendant drop technique. Measurements of Interfacial thickness are also difficult. They have been made using electron microscopy and, mostly in the case of block copolymers, by x-ray and neutron scattering. Recent results using neutron reflection suggest that this will be a useful technique in the future. 

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