Freeze fracture surfaces

Figure 6. Scanning electron micrographs of freeze-fracture surfaces for injection molded (A), dioxane cast (B), and pyridine cast (C) blends at a composition of 15% lignin. (2000X) (From ref. 10, with permission of But-terworth ic Co., Ltd.)...

Figure 5 presents the results of tensile tests for the HPC/OSL blends prepared by solvent-casting and extrusion. All of the fabrication methods result in a tremendous increase in modulus up to a lignin content of ca. 15 wt.%. This can be attributed to the Tg elevation of the amorphous HPC/OSL phase leading to increasingly glassy response. Of particular interest is the tensile strength of these materials. As is shown, there is essentially no improvement in this parameter for the solvent cast blends, but a tremendous increase is observed for the injection molded blend. Qualitatively, this behavior is best modeled by the presence of oriented chains, or mesophase superstructure, dispersed in an amorphous matrix comprised of the compatible HPC/OSL component. The presence of this fibrous structure in the injection molded samples is confirmed by SEM analysis of the freeze-fracture surface (Figure 6). This structure is not present in the solvent cast blends, although evidence of globular domains remain in both of these blends appearing somewhat more coalesced in the pyridine cast material.

Samples in the SEM can be examined "as is" for general morphology, as freeze fractured surfaces or as microtome blocks of solid bulk samples. Contrast is achieved by any one or combination of the following methods ... 

One method of communication between cells is by passage of chemical substances through special junctions which, because of their appearance in electron micrographs of thin sections (Fig. 1-15, G) are known as gap junctions. T45,146 Q p junctions may cover substantial areas of the cell interface. In cross section, a thin 3-4 nm gap between the adjacent cell membranes is bridged by a lattice-like structure, which may appear in freeze-fractured surfaces as a hexagonal array of particles (Fig. 1-15, F, lower junction). These particles or connexons are each thought to be composed of six protein subunits. A central channel in the connexon is able to pass molecules of molecular mass up to about 500 Small molecules may be able to pass... 

Figure 10.4. Micrograph of a freeze-fractured surface of an HDPE/PA-6 extruded blend, showing tree ring structures typical of telescopic flow in the capillary, caused by interlayer slip [Dumoulin et al., 1986].

Figure 21.24 SEM micrographs of freeze-fractured surface of (a) PP/CB (100/11) and (b) epoxy/CB (100/20) composites. (From Reference 60 with permission from Wiley Interscience.)...

Scanning electron micrograph of consolidated UHMWPE, showing freeze-fractured surface. 

Figure 7.10 SEM micrographs of freeze-fractured surface of PLA/NR (a) and PLA/NR-g-PVAC blends at different PVAc contents 1% (b), 5% (c) and 12% (d).

Freeze-etching Technique in which water is evaporated under vacuum from the freeze-fractured surface of a specimen before the observation with electron microscopy. 

Fig. 2.11 Topographical and phase contrast AFM images for freeze fracture surfaces for two analogous materials they differ only in the type of diisocyanate, (a) (DBDI BDO PTHF) (b) MDI BDO PTHF. Courtesy by Mrs. I. Stoica, Institute of Macromolecular Chemistry, Petru Poni, Iasi, Romania...

Normally, the surface of a PU sample fracture shows a relief composed of peaks of HS and crystal aggregates domains. The rupture occurrs most probably in the amorphous regions. Therefore, it is expected that such a surface contains more information about the sample morphology than the surface of free solidification or drying. AFM images were taken from different zones for each sample. Shown in Fig. 2.24 are images of freeze fracture surfaces for the whole series of the materials (PUi to PUs). 

AFM topographic 3D and 2D images for freeze fracture surfaces for materials listed in Tables 2.4 and 2.5 [207]... 

FIGURE 19.5 SEM images of freeze-fracture surface of (a) neat PLA, (b) PLA/C18MMT5, and (c) PLA/qC18MMT5 foams [74]. Reproduced from Ref. 74 with permission of Wiley-VCH Verlag GmbH, Germany. 

Figure 8. SEM of freeze-fracture surfaces. (A) pectin (B) 70 30pectin/PVOH iO 50 50 pectin/ PVOH (D) 30 70 pectin/PVOH (E) PVOH (F) phase contrast image, 50 50pectin/PVOH (Reproduced from reference 10. Copyright 1998.)...

Figure 3.17. SEM images of freeze-fractured surfaces of (a) untreated nano-silica/PP (iiano-silica content = 0.95 vol%), (b) poly(p-vinylpheiiylsulfonylhydrazide) grafted nano-silica/PP composites (nano-silica content = 1.43 vol%), and (c) poly(p-vinylphenylsulfonylhydrazide) grafted nano-silica/PP composites (nano-silica content = 2.41 vol%)...

FIGURE 19.3 Low voltage scanning electron micrograph of permanganic etched freeze fracture surface of UHMWPE. 

Fig. 43. Transmission electron micrograph of a replica of a freeze-fractured surface of polyethyleneoxide M =6,000 in PHEMA [11]. The pore channels have a width of about 10 nm...

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