Fibrillar microstructures

The regular fibrillar microstructure of some large intrinsic crazes and their dense arrangement are shown in the scanning electron micrograph in Figure 7. A quantitative analysis will be given in Section 5.2 by means of SAXS. 

Fig. 7. Scanning electron micrograph of the fibrillar microstructure of crazes II...

Fig.29. Fibrillar microstructure of stress-whitened zones in poly(ethylene terephthalate) as revealed by scanning electron microscopy...

The structural analysis of intrinsic crazes in PC has been carried out by SAXS. The fibrillar microstructure of these crazes gives rise to pronounced scattering effects which enable a detailed analysis of the craze structure in terms of both the voliune fraction of craze fibrils and of the fibril diameter. This analysis showed that the microstructure of intrinsic and extrinsic crazes is largely different. There exists some evidence that the distinct microstructure primarily reflects the different stress-strain states of the matrix at craze initiation. Further investigations are necessary to answer... 

Fig. 26a and b. TEM-micrographs of ultrathin sections cut parallel to the stress-whitened surface of particle modified PETP. Dark portions in a represent the rubber-like particles which appear to encourage craze initiation in the matrix polymer, b represents the voidy and fibrillar microstructure in one of these crazes (arrow = stress direction)... 

The regular fibrillar microstructure gives rise to pronounced scattering effects. Quantitative analysis by SAXS shows that the product remaim approximately constant as a function of temperature and strain rate. However, a. D decreases as a function of diluent concentration. 

As indicated in Figure 7b and 8b, the outer skin layers were fibrillar microstructures in nature and were oriented parallel to the flow direction. The high orientation observed could be attributed to the elongational flows that seem to predominate nearthe surface of the mold. The skin layers were approximately 20-50 pm in thickness. 

Chemstrand s Acrilan process was based on a wet-spinning technology, which produces a fibrillar microstructure. As a result, early acrylic fiber products suffered from problems with abrasion originating with a lack of coherence in the fibrillar surface of the fibers. This was overcome by adding a steam-annealing step, which, combined with the presence of vinyl acetate as comonomer, makes the fibrils that compose each filament fuse together. 

Fig. 12.19 A TEM micrograph of a mature craze in glassy PS, showing the fibrillar microstructure of the craze and the central mid-rib layer of thickness roughly 100 nm of more highly oriented portions of fibrils with A = 5.7 (from Kramer and Berger (1990) courtesy of Springer).

Figure 30 Fibrillar nanowires formed by the directed self-assembly of a PEO-Woc/(-peptide-Woc/(-tetrathiophene-Woc/f-peptide-Woc/f-PEO ABA conjugate (right). AFM micrograph of the fibrillar microstructures with the inset showing the left-handed superhelical fine structure before switching (left). Adapted from Schillinger, E.-K. Mena-Osteritz, E. Hentschel, J. etal. Adv. Mater. 2009, 21,1562." ...

Gomillion BE. Fiber production with in-situ formation of fibrillar microstructures by chaotic mixing. PhD dissertation. Clemson University 2000. 

Fig. 13 pH-controlled switch of a polymer—peptide conjugate with two switch defects in the peptide segment two-step process from the fully disturbed peptide segment (left) via two intermediate structures (middle ) to the undisturbed aggregator (right) after RAFT polymerization results in a fibrillar microstructure. Reprinted with permission from [108]. Copyright (2007)... 

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