Cryo-fractures

Fig.18a-b. Scanning electron micrographs on cryo fractured surfaces of a macroporous epoxy prepared with 6 wt % hexane via the Cl PS technique showing a narrow size distribution b macroporous epoxy prepared with 7.5 wt % hexane via the CIPS technique showing a narrow size distribution. Reprinted from Polymer, 37(25). J. Kiefer, J.G. Hilborn and J.L. Hedrick, Chemically induced phase separation a new technique for the synthesis of macroporous epoxy networks p 5719, Copyright (1996), with permission from Elsevier Science... 

Abis and co-workers [32,33] reported on a multi-technique characterization of immiscible blends between sPS and several polyolefins, prepared in a mixer at 285 °C and thermo-compressed at the same temperature. SEM performed on the cryo-fractured surface of the blends shows a gross phase separation, while the presence of voids due to the easy pull-off of particles from cryo-fractured surfaces points to a lack of adhesion between components (Figure 20.4a). The particles of polyolefins present in 80 20 wt% blends have dimensions decreasing in the following order PP LLDPE > HDPE > EPR > PIB. 

Figure 20.4 SEM of sPS/HDPE blend cryo-fractured surfaces (a) 80 20 wt%, (b) 20 80 wt%. Reprinted from Ref. 33 by permission of Wiley-VCH...

Fig. 3.27 Scanning electron micrographs of the cryo-fractured surfaces of unvulcanized natural rubber/CW obtained by casting and evaporating (a) and freeze-drying and hot-pressing (b) [39]...

The effect of the reactive compadbilizatimi can be observed aheady during mixing by comparing the viscosity (detected e.g. as torque necessary to keep the mixing speed constant) over time curves. Furthermore, the size of the dispersed PA6 particles (mostly the minor phase forms particles dispersed in the major phase) can be analysed in the blends before and after compression moulding. By optical microscopy on thin cuts (or in the reflected light mode on cryo-fractures) in the nonreactive PP/PA6 blend particles in the size of few pm can be detected while in the reactive PP-MA/PA6 blend the PA6 phase is so small (100 nm scale) that... 

Fig. 18.7 Dispersion of rayon fibers after pellet opening during compounding - SEM cryo fracture surface of injection molded test specimen...

Fig. 18.9 SEM cryo fracture micrographs for uncoupled left) and coupled right) rayon-PP composites [3 wt% PP-g-MAH coupling agent, from Ganster and Fink [7]]...

That this mechanism leads to successful bonding indeed is demonstrated with the SEM cryo fracture micrographs in Fig. 18.21 of composites with 20% rayon and 1 wt% HMDI produced on a 100 g scale using akneader. Three cases are shown the... 

Fig. 18.21 SEM cryo fracture micrographs of PLA-rayon composites with strong left), moderate middle), and weak right) interphase...

The effects might be even more obvious in Fig. 18.22, where a lower magnification of cryo fracture surfaces of the same composites is presented. Almost no fiber stumps are detected for the strong, HMDI-coupled interphase (left) while medium length stumps/pullouts are found for the normal case without CA (middle), and extremely long pullouts are visible for the so-called weak interphase (right). 

Figure 6.5. Cryo-fractured FESEM images of PEI/MWNT composites with (a) 0.5 wt% and (b) 1.0 wt% MWNT. Reproduced from 46] with permission from lOP Publishing Ltd...

Lehn and coworkers investigated vesicle aggregation and fusion mediated by the coordination of Eu " to an amphiphilic diketone. ° The addition of Eu(N03)3 induced an increased average size of the vesicles which could be detected by cryo-fracture electron microscopy. The interaction of vesicles induced by Ni " " and Co " binding to an amphiphilic dipyridine was also reported by Lehn and coworkers. The addition of Ni " " and Co " " ions to a solution of LUVs containing 3 mol% of amphiphilic dipyridine led to fusion of LUVs and formation of MLVs (Figure 9). To investigate the fusion process, LUVs were fluorescently labeled with rhodamine. 

The morphology of the cryo fractured of a poultry feather, the cross section of the rachis and the composites was analyzed by environmental scanning microscope (ESEM) -Philips XL 30. 

Figure 22.15 SEM micrographs of cryo-fractured and chloroform etched surfaces cut parallel to the extrusion direction (a) blend containing 70wt% PP (b) blend containing 80wt% PP. Harrats et al. [78], Reproduced with permission of Elsevier.

SEM images after cryo-fracture of (a) a conventional coating system and (b) a microcapsuie-containing coating system... 

Mechanical properties of natural fiber reinforced composites are mainly influenced by the level of dispersion and interfacial adhesion between the matrix and fibers and microscopy is one of the most effective methods for morphological observations. In this study, scanning electron microscope (SEM) was used to investigate the dispersion of natural fiber and interfacial morphologies and the images are shown in Figures 3.2 (film surface) and 3.3 (cryo fractured surface). The SEM pictures show the differently shaped particles and the more or less spherical lignin-based particles. 

The cryo-fractured surfaces of composite films were analyzed by SEM to study morphological and interfacial characteristics and the micrographs are shown in Figure 3.3. The brittle-fractured surface of uncompatibilized composite film (Figure 3.3a) shows wide gap between the fiber and matrix with significant presence MMT clusters, which decreases film homogeneity [7]. Further, these features provide an evidence of decrease in... 

Novel olefin block copolymers synthesized via catalytic block technology were evaluated for polyolefin blend compatibilization. It was found that OBC is an effective polyolefin blend compatibilizer for polypropylene-high density polyethylene blend. Significant improvements in mechanical properties were observed. Morphology showed that OBC compatibilized blends displayed reduction in phase size. Cryo-fractured surface analysis and adhesion data from microlayered tapes with OBC as tie layers suggested improved interfacial adhesion for OBC compatibilized blends. 

The mechanical properties, morphology and cryo-fractured surface of blends were evaluated to determine the efficiency of OBC as a blend compatibilizer. It was found that OBC multi-block copolymers can efficiently compatibilize PP/HDPE blends. The addition of OBC results in a significant reduction of domain size forming a shell around a HDPE core. The mechanical property of the blend has been... 

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