Network domination

Zhang et al. studied the effect of conductive network formation in a polymer melt on the conductivity of MWNT/TPU composite systems (91). An extremely low percolation threshold of 0.13 wt% was achieved in hot-pressed composite film samples, whereas a much higher CNT concentration (3-4 wt%) is needed to form a conductive network in extruded composite strands. This was explained in terms of the dynamic percolation behavior of the CNT network in the polymer melt. The conductivity of extruded strand showed a hopping resistivity dominated behavior at low concentrations and a dynamic percolation induced network dominated behavior at higher concentrations. It was shown that a higher temperature can reduce the filler concentration required for the dynamic percolation to take effect. 

The GC-MS analyses of Murchison, Orgueil and Cold Bokkeveld macromolecular material indicate that the macromolecular materials in different meteorites are qualitatively veiy similar (e.g. made up of the same units) 11), In addition, oxygen-, sulfur- and nitrogen-containing moieties such as phenols, thiophenes and benzonitrile have also been detected in the pyrolysates. The H2-pyrolysis further demonstrated that the refractory component probably consists of a network dominated by at least five- or six-ring PAH units that are crosslinked together 13). 

In summary, imidazolium-based ELs display a high degree of self-organization in the liquid state. Both theoretical and experimental studies showed that a three-dimensional ioific network dominated by electrostatic interactions coexists with... 

Nonhydrodynamic effects of filler particles (e.g., filler networking) dominate the low shear behavior in such a manner that an apparent yielding region overrides the pseudo-Newtonian plateau of the polymer matrix (corresponding to parameter TI02)... 

Pour-Point Depressants. The pour point of alow viscosity paraffinic oil may be lowered by as much as 30—40°C by adding 1.0% or less of polymethacrylates, polymers formed by Eriedel-Crafts condensation of wax with alkylnaphthalene or phenols, or styrene esters (22). As wax crystallizes out of solution from the Hquid oil as it cools below its normal pour point, the additive molecules appear to adsorb on crystal faces so as to prevent growth of an interlocking wax network which would otherwise immobilize the oil. Pour-point depressants become less effective with nonparaffinic and higher viscosity petroleum oils where high viscosity plays a dominant role in immobilizing the oil in a pour-point test. 

An entirely new concept was iatroduced iato mbber technology with the idea of "castable" elastomers, ie, the use of Hquid, low molecular-weight polymers that could be linked together (chain-extended) and cross-linked iato mbbery networks. This was an appealing idea because it avoided the use of heavy machinery to masticate and mix a high viscosity mbber prior to mol ding and vulcanization. In this development three types of polymers have played a dominant role, ie, polyurethanes, polysulftdes, and thermoplastic elastomers. 

At high rates of strain, or when complete disentanglement cannot occur when M > M, bond rupture occurs randomly in the network and the percolation parameter p becomes dominated by chain ends such that... 

In order to account for both micromixing and mesomixing effects, a mixing model for precipitation based on the SFM has been developed and applied to continuous and semibatch precipitation. Establishing a network of ideally macromixed reactors if macromixing plays a dominant role can extend the model. The methodology of how to scale up a precipitation process is depicted in Figure 8.8. 

The structures of boron-rich borides (e.g. MB4, MBfi, MBio, MB12, MBe6) are even more effectively dominated by inter-B bonding, and the structures comprise three-dimensional networks of B atoms and clusters in which the metal atoms occupy specific voids or otherwise vacant sites. The structures are often exceedingly complicated (for the reasons given in Section 6.2.2) for example, the cubic unit cell of YB e has ao 2344 pm and contains 1584 B and 24 Y atoms the basic structural unit is the 13-icosahedron unit of 156 B atoms found in -rhombohedral B (p. 142) there are 8 such units (1248 B) in the unit cell and the remaining 336 B atoms are statistically distributed in channels formed by the packing of the 13-icosahedron units. 

All of the studied polymers are described by the network scheme in Fig. 2.1. Consequently, the composition of the polymers is uniform but the molecular chains between crosslinks differ in length. The molecular mass between crosslinks is therefore a dominant parameter for the characterization of the networks. 

Broutman and McGarry [98] examined the effects of crosslinking on toughness as early as 1965. Bell [99] observed a threefold increase in notched impact strength as the molecular mass between crosslinks was increased. Schmid et al. [100] and Lohse et al. [101] pointed out the dominating effect of molecular strand length on the ultimate properties and the toughness of crosslinked polymers. Later, Batzer et al. [46], Schmid [44], and Fischer et al. [45] compared the behavior of various networks composed of epoxy resins. 

The degradation of the matrix in a moist environment strongly dominates the material response properties under temperature, humidity, and stress fatigue tests. The intrinsic moisture sensitivity of the epoxy matrices arises directly from the resin chemical structure, such as the presence of hydrophilic polar and hydrogen grouping, as well as from microscopic defects of the network structure, such as heterogeneous crosslinking densities. 

The structure of a-C H DLC consists of an essentially amorphous network with isolated clusters dominated by the sp configuration (graphite) with some sp (diamond). Hydrogen is believed to play an essential role in determining the bonding configuration by helping to form the sp bond, probably in a manner similar to the formation of CVD diamond. 

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