Microscopic Observation under TEM

The TEM observation after staining with RuOa provides us with a high definition view of the microscopic mechanisms and reveals the specific role of the POE phase. In the BD13 blend, illustrated in Fig. 19.30a, three phenomena are visible (i) interfacial debonding at the poles of PA6 particles, (ii) high elongation of hyperelastic POE particles, and (iii) cavitation in dispersed POE droplets. On the whole, since the size and number of POE particles are smaller than that of PA6 particles, the former mechanism is more frequently observed and seemed to have a leading influence on the overall volume strain. 

For BD15, with an alloying content of 45 wt%, as shown in Fig. 19.30c, the cavitation at the poles of PA6 particles seems to result more from the cavitation of the POE interphase than from a simple interfacial debonding (although it is not always simple to make the difference). Also, the cavitation in dispersed POE droplets is very active. Furthermore, in some micrographs a new type of salami structure is present large POE nodule containing small PA6 inclusions. Under uniaxial tension, the POE of these salami stmctures deforms easily, while the PA6 particles inside seem unaffected. 

At last for BD16 (Fig. 19.30d), in which PP is in minority, cavitation occurs more likely in POE interphase at the poles of large PA6 particles and in large isolated POE particles (that are more numerous in this blend). However, conservative deformation mechanisms become predominant and are commonly identified (i) at smaller POE droplets, (ii) at salami structures, and (iii) in the PP matrix. 

The above morphological characterization helps us to understand the influence of composition on the dilatation of the materials under uniaxial tension. 

For neat PP, the crazing mechanisms have been the object of many previous papers (41,49,50). It was shown that crazes resulting from early fragmentation of the crystalline stacks propagate in the amorphous phase between the lamellae along the radial directions as shown in Fig. 19.31. At higher strain, the cracks are rotated and become nearly parallel to the tensile direction. It is remarkable that although such 

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