Structure and Properties of MFCs

It can be concluded that although transcrystallization was observed in some MFC systems, as yet this phenomenon is far from being completely imderstood. As MFCs belong to the fiber reinforced composites, their mechanical properties wUl be expected to depend, just like the conventional fiber composites, on the effectiveness of the transfer of stress between the fiber and matrix [87], i.e., on the structure and geometry of the TCL. 

Many research efforts have probed the structure-dependent properties of Au MFCs, utilizing core doping as a tactic. As with the Fd/Ft bimetallic clusters, doping of the core can result in dramatically different nanoparticle properties, inviting further study and understanding. Most known examples of alloyed nanoclusters contain Au. 

The first structural investigations of Prussian blue analogs date back to 1936 when Keggin and Miles (2) studied the X-ray powder patterns of iron cyanides. They found a luiit cell of the face-centered type and deduced a structural model from these geometrical data. This description, which will be briefly outlined below, has until recently been accepted by many authors (3, 39—44) for the discussion of the structural properties of cubic polynuclear cyanides Mfc[M (CN)e]i cHgO. In many cases the physically equivalent description has been used 3, 42,... 

Table 14.13. Relationships between some structural parameters of the reinforcing fibrils in HDPE/PA/YP MFC as revealed by SEM and WAXS studies and the mechanical properties of the respective material...

The characteristic MFC structure in the PET/PP blends could be created after compression molding as well as after injection molding at temperatures below of PET, although in the case of IM, the distribution of the PET fibrils in the PP matrix is almost random. The flexural strength and modulus of the IM blends with MFC structure are superior by60-70% to those of the neat PP and blends without an MFC structure this fact demonstrates the reinforcing effect of the PET fibrils. The compression molded PET/PP and LCP/PPE samples with an MFC structure possess much better mechanical properties in the draw direction than those of the IM specimens, because of the uniaxial orientation of the PET and LCP fibrils. 

In an early work, it was shown that electrocatalytic currents can be enhanced by utilizing MFCs. The electrocatalytic reduction of 1,1-dinitrocyclohexane by electrogenerated anthraquinone radical anions incorporated into the ligand shell of a 2 nm Au MFC was compared to the reactivity of monomeric anthraquinone. ET rate constants of MFC-bound anthraquinone were nearly identical to the monomeric rates, but catalytic currents were higher for the anthraquinone-MFC catalysts, which was attributed to its smaller diffusion coefficient and consequent compressed reaction layer. This represents an example of decorating the surface of the MFC with catalytically active moieties, but the core-shell structure of a nonredox ligand-modified MFC can be exploited for its electrocatalytic properties as well. 

Microfibrillar cellulose (MFC) is a basic structural component of wood fibers, one of the most abundant biological raw materials on the planet. Recently, the potentialities of MFC as a renewable, abundant and biodegradable material have attracted increasing interest. Some examples of uses envisaged are MFC as a reinforcement material in composites, as a component in wood- and paper-based products with enhanced strength properties and built-in advanced functionalities, and as an additive for control of the stability and rheology of emulsions, suspensions and foams. 

Special attention was paid to the structure-property relationships of blends involving polyolefins, especially PP and PE, as lower-melting components acting as matrices in MFCs, and PET as the higher-melting component, forming the microfibrillar reinforcing elements [45]. 

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