The Matrix Phase

Table 13 is a representative Hst of nickel and cobalt-base eutectics for which mechanical properties data are available. In most eutectics the matrix phase is ductile and the reinforcement is britde or semibritde, but this is not invariably so. The strongest of the aHoys Hsted in Table 13 exhibit ultimate tensile strengths of 1300—1550 MPa. Appreciable ductiHty can be attained in many fibrous eutectics even when the fibers themselves are quite britde. However, some lamellar eutectics, notably y/y —5, reveal Htde plastic deformation prior to fracture. 

For a fiber immersed in water, the ratio of the slopes of the stress—strain curve in these three regions is about 100 1 10. Whereas the apparent modulus of the fiber in the preyield region is both time- and water-dependent, the equiUbrium modulus (1.4 GPa) is independent of water content and corresponds to the modulus of the crystalline phase (32). The time-, temperature-, and water-dependence can be attributed to the viscoelastic properties of the matrix phase. 

However, a substantial improvement in impact energies of PP-NBR blends with GMA or IPO functionalized PPs is observed. The PP-NBR blends went through a brittle-ductile transition as the concentration of the functionalized PPs in the matrix phase reached a leveling off at 13 wt% in the case of IPO functionalized PP and 25 wt% in the case of GMA functionalized PP. Up to a ten-fold improvement in impact energy was observed when the brittle-ductile transition was reached. 

An additional requirement is that the reactant material must have two phases present in the tie-triangle, but the matrix phase only one. This is another way of saying that the stability window of the matrix phase must span the reaction potential, but that the binary titration curve of the reactant material must have a plateau at the tie-triangle potential. It has been shown that one can evaluate the possibility that these conditions are met from knowledge of the binary titration curves, without having to perform a large number of ternary experiments. 

The kinetic requirements for a successful application of this concept are readily understandable. The primary issue is the rate at which the electroactive species can reach the matrix/reactant interfaces. The critical parameter is the chemical diffusion coefficient of the electroactive species in the matrix phase. This can be determined by various techniques, as discussed above. 

Conventional Systems. In the conventional antifouling compositions, the organotin compound (TBTO, TBTF, TBTC1, TBTOAc) is mechanically mixed into the paint vehicle. When the TBT species is completely soluble in the polymer matrix, factors (a) and (b) become unimportant in most cases. The mobile species is already present its diffusion in the matrix, phase transfer and migration across the boundary layer into the ocean environment may be represented by Figure 2a. When the organotin compound forms a dispersed second phase, rate of its dissolution in the polymer matrix becomes another factor to consider. 

In addition to the cavitation process related to the presence of a dispersed phase, the formation of voids in the plastic zone has been observed to occur also in the matrix phase. Kinloch and Huang stated that the plastic void growth succeeding cavitation also contributes to energy absorption and might become as important as the shear banding, especially at fairly elevated temperatures [161]. 

Another major use of butadiene polymer is in the manufacture of HIPS. Most HIPS has about 4%i-12%i polybutadiene in it so that HIPS is mainly a PS-intense material. Here, the polybutadiene polymer is dissolved in a liquid along with styrene monomer. The polymerization process is unusual in that both a matrix composition of PS and polybutadiene is formed as well as a graft between the growing PS onto the polybutadiene is formed. The grafting provides the needed compatibility between the matrix phase and the rubber phase. The grafting is also important in determining the structure and size of rubber particles that... 

Similar arguments explaining the phase separation were employed by Chou et al. [44]. The dynamics of phase separation was observed using an optical microscope during the course of polyurethane-unsaturated polyester IPN formation at different temperature. Chou et al. suggested that an interconnected phase formed through the spinodal decomposition mechanism developed quickly and was followed by the coalescence of the periodic phase to form a droplet/matrix type of morphology. The secondary phase separation occurred within both the droplet and the matrix phases. Chou et al. did not explain, however, why secondary phase separation occurred. 

Suppose that a two-phase system consists of a fine dispersion of a carbide phase in a matrix. The carbide particles are in equilibrium with C dissolved interstitially in the matrix phase, with the equilibrium solubility given by... 

Stage I is the incubation period in which the matrix phase is metastable and no stable particles of the new phase have formed. Nevertheless, small particles (termed clusters or embryos) which are precursors to the final stable phase continuously form and decompose in the matrix. The distribution of these clusters evolves with increasing time to produce larger clusters which are more... 

The substrate/silane interphase and the silane/matrix interphase are equally important in considering the mechanism of reinforcement by silane coupling agents in composites. The mineral oxide/silane interphase is more well defined than a metal/silane or a silane/matrix interphase. For example, in the case of a metal substrate, surface oxides may dissolve into the silane layer or form a complex. In the case of the silane/matrix interphase, a diffuse boundary layer may exist due to dispersion of physisorbed silanes in the matrix phase or penetration of the matrix resin into chemisorbed silane layers. Many features of the interaction of a silane coupling agent with a polymer matrix are specific to the system, and thus the chemistry of the silane/matrix interphase must be characterized and defined for each system. 

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