Intercomponent adhesion level

The parameter calculation according to the stated above technique shows its decrease (intercomponent adhesion level enhancement) at testing temperature raising within the range of 500 a-130. 

As it has been shown in Ref. [48], the interfacial (or intercomponent) adhesion level depends on a number of accessible for the formation interfacial (intercomponent) bond sites (nodes) on the filler (nanocluster) particle surface N, which is determined as follows [49] ... 

Hence, the stated above results have demonstrated, that intercomponent adhesion level in natural nanocomposites (polymers) has structural origin and is defined by nanoclusters relative fraction. In two temperature ranges two different reinforcement mechanisms are realized, which are due to large friction between nanoclusters and loosely packed matrix and also perfect (by Kemer) adhesion between them. These mechanisms can be described successfully within the frameworks of fractal analysis. 

The further study of intercomponent adhesion in natural nanocomposites was fulfilled in Ref [50]. In Fig. 15.18, the dependence bJ T) for PC is shown, from which b reduction or intercomponent adhesion level enhancement at testing temperature growth follows. In the same figure the maximum... 

In Fig. 15.20, the dependence of on the difference is adduced, from which decrease or intercomponent adhesion level enhancement at... 

Hence, the stated above results have demonstrated, that interactions nanoclusters-loosely packed matrix type (large friction or perfect adhesion) is defined by nanoclusters butt-end and side (cylindrical) surfaces areas ratio or their geometry if the first from the mentioned areas is larger that the second one then a large friction nanoclusters-loosely packed matrix is realized if the second one exceeds the first one, then between the indicated structural components perfect adhesion is realized. In the second from the indicated cases intercomponent adhesion level does not depend on the men-... 

Hence, the analogy in behavior of reinforcement degree of polyarylate by nanoclusters and nanocomposite epoxy pol5mier/Na -montmorillonite by layered silicate gives another reason for the consideration of polymer as natural nanocomposite. Again strong influence of interfacial (intercomponent) adhesion level on nanocomposites of any class reinforcement degree is confirmed [17],... 

The degree of chaos is the general characteristic of the structure and therefore it should influence both structural parameters and properties of epoxy polymers. It has been shown earlier that epoxy polymers can be considered as natural nanocomposites, for which the interfacial (intercomponent) adhesion level is one of the most important characteristics [34]. For polymer composites (nanocomposites) this property can be characterised by the parameter b, estimated according to the equation [35] ... 

The detailed methods of calculation of OC p and O-ep are adduced in paper [35] and the experimental a p values are accepted according to the data of paper [7]. In Figure 9.9 the dependence is adduced, from which approximately quadric growth in b or raising of the intercomponent adhesion level with increasing or the degree of chaos in the structure of the considered epoxy polymers follows. 

Hence, the results stated above have demonstrated a high level of stress concentration in the loosely packed matrix, which is due to an essential change in its structure, for crosslinked epoxy polymers, treated as natural nanocomposites. Let us note that high values of the stress concentration factor are due to the indicated fractality of the structure and for a loosely packed matrix the Euclidean structure stress concentration is absent. The increase of the stress concentration factor, characterising the degree of change in structure, raises the strength of the epoxy polymers, but simultaneously reduces the intercomponent adhesion level. 

The intercomponent adhesion level can be estimated quantitatively with the aid of the parameter b (Figure 9.9), which is determined by an independent method using the thermal expansion coefficient of epoxy polymers. In Figure 9.27 the curves 1-3 represent three basic types of the dependences of the linear thermal expansion coefficient of the considered epoxy polymers on the relative contents of nanoclusters. The straight line 1 illustrates the case when adhesion is absent between two structural components of natural nanocomposite and at the thermal expansion coefficients of the loosely packed matrix and nanoclusters, respectively) the loosely packed matrix will expand on heating independently from... 

The parameter b can be estimated with the aid of Equation 9.13. The calculations according to this equation gave the mean value b 0.20 (Figure 9.9). The parameter b allows precise qualitative gradation of intercomponent adhesion level. So, the condition b = 0 means absence of the indicated adhesion and b = 1.0 indicates perfect (by Kerner) adhesion. The value b 0.20 defines a low, but different from zero, intercomponent adhesion level, that completely corresponds to the data of Figure 9.26, where the experimental points are located somewhat higher than the curve 2, calculated according to the condition of zero intercomponent adhesion. 

Amorphous glassy polymers as natural nanocomposites puts forward to the foreground their study intercomponent interactions, that is, interactions nanoclusters - loosely packed matrix. This problem plays always one of the main roles at multiphase (multicomponent) systems consideration, since the indicated interactions or interfacial adhesion level defines to a great extent such systems properties [42]. Therefore, the authors of Ref. [43] studied the physical principles of intercomponent adhesion for natural nanocomposites on the example of PC. 

Thus, the results stated above have demonstrated the principal distinction between linear and crosslinked polymers under their consideration as natural nanocomposites - if for the former nanoclusters are the reinforcing element (analogue of nanofiller) at the definition of reinforcement degree, then for the latter the loosely packed matrix is such an element. This distinction is due to the different type of bonds in the loosely packed matrix - for linear polymers there are relatively weak intermolecular (van der Waals) bonds and for crosslinked polymers covalent bonds. The level of intercomponent adhesion between nanoclusters and the loosely packed matrix for the... 

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