Double networking structure

In Sect. 2, a double network structure was proposed for the PVA films in the water-swollen state, i.e. an amorphous chain (tie chain) network and a fibrillar network. The blue color complex is considered to be formed mostly in the former network. Subsequently what happens in PVA films during soaking in aqueous solutions were discussed. The contractions of the volume and the long... 

Networks can also be formed from chains in the deformed state. In this approach a first network is generally introduced in the undeformed state, the resulting elastomer is elongated, and a second network is introduced in the stretched state. Release of the stress permits the network to retract, but the second network of this double-network" structure prevents retraction down to the original dimensions (figure 7.4). The most interesting feature of the retracted network is the fact that it is anisotropic in structure and properties. 

The nonlinear viscoelastic behavior of filled vulcanizates is somewhat different from that of filled compounds, since the chemical crosslink network of the rubber matrix is formed and, the physical rubber-filler networks and filler-filler networks are enhanced during curing at a relatively high temperature [7]. Speaking from a broad sense, filled vulcanizates can be viewed as a double network structure in which the nanoparticles supplement the inherent viscoelasticity of crosslink rubbers with additional physical network junctions. 

Acrylic and methacrylic acids and their esters are highly versatile materials in that the acid and ester side groups can partake in a variety of reactions to produce a very large number of polymerisable monomers. One particularly interesting approach is that in which two methacrylic groupings are linked together so that there are two, somewhat distant, double bonds in the molecule. In these cases it is possible to polymerise through each of these double bonds separately and this will lead eventually to a cross-linked network structure. 

The unique properties of SDIBS are due to the branched structure of the DIB core, and consequently the double-network stmcture in which a covalent network is embedded into a self-assembling thermolabile network, as shown in Figure 7.9. 

D-TEM gave 3D images of nano-filler dispersion in NR, which clearly indicated aggregates and agglomerates of carbon black leading to a kind of network structure in NR vulcanizates. That is, filled rubbers may have double networks, one of rubber by covalent bonding and the other of nanofiller by physical interaction. The revealed 3D network structure was in conformity with many physical properties, e.g., percolation behavior of electron conductivity. 

Polymers of dienes such as butadiene frequently contain a substantial portion of gel which will not dissolve in a good solvent, though it may swell to a volume 20 to 100 or more times that of the polymer itself. This gel, which may comprise up to 90 percent or more of the polymer, consists of a space-network structure formed as a result of a very few cross-linkages provided by occasional (perhaps 1 in 1000 or less) diene units both double bonds of which have entered into the polymerization (see Chap. VI). 

Very recently, attempts have been made to develop PP/EOC TP Vs. In order to make TPVs based on PP/EOC blend systems, phenolic resin is ineffective because the latter needs the presence of a double bond to form a crosslinked network structure. Peroxides can crosslink both saturated and unsaturated polymers without any reversion characteristics. The formation of strong C-C bonds provides substantial heat resistance and good compression set properties without any discoloration. However, the activity of peroxide depends on the type of polymer and the presence of other ingredients in the system. It has been well established that PP exhibits a (3-chain scission reaction (degradation) with the addition of peroxide. Hence, the use of peroxide only is limited to the preparation of PP-based TPVs. Lai et al. [45] and Li et al. [46] studied the fracture and failure mechanism of a PP-metallocene based EOC based TPV prepared by a peroxide crosslinking system. Rajesh et al. 

A surface reconstruction containing the same structural elements as the one of Au(lll) has been recently found in Pt(lll) above 1330K [12] or under an excess of Pt adatoms at 400 K [13]. The reconstructed surface layer has an atomic density larger than a (111) plane in the bulk. Regions of fee and hep stacking are separated by bright double dislocation lines along [112], which, contrary to Au(lll), can meet and form a network structure with star-like features [13]. 

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