Droplet-in-matrix

Typical droplet-in-matrix (or dispersed type) phase morphology in melt-blended binary blend. Scanning electron microscopy (SEM) photomicrograph of a cryofractured surface of 80 wt% polystyrene/20 wt% polypropylene melt-mixed blend. (From G. Lei, Development of Three Phase Morphologies in ReacHvely CompattbUized Polyamide 6/Polypropylene/Polystyrene Ternary Blends, master s thesis, Katholieke Universiteit Leuven, Belgium, 2004.)... 

There exist in polymer blends two or three major types of phase morphologies, depending on whether the encapsulated structures (composite droplets) are considered as a class apart. The most common is the droplet-in-matrix (as, for example, Figure 1.3), the (droplet-in-droplet)-in-matrix (as, for example. Figure 1.4), and the cocontinuous phase morphology where both phases are mutually interconnected throughout the whole volume of the blend (as, for example. Figures 1.5 and 1.6). 

Droplet-in-Matrix Phase Morphology (Dispersed Morphology)... 

A droplet-in-matrix phase morphology developed in immiscible polymer blends depends on the viscoelastic properties and composition of the two components of the blend in the melt state. The rheological formalism used for the non-Newtonian phases as polymer melts follows, with adjustment of the... 

Contrary to the droplet-in-matrix, the mechanism and the control of the co-continuous phase morphology, where the two phases are continuous and interconnected throughout the whole volume of the blend, is still not well elucidated. The complexity arises mainly from the ambiguous effect of the viscoelastic characteristics of the components, their composition in the blends, and the magnitude of their interfacial tension. Several empirical expressions have been proposed so far to predict either the phase inversion or the conditions for which co-continuous morphology is generated. 

We decided to rank apart the phase morphology in ternary immiscible blends because it can be droplet-in-matrix, co-continuous, or a mixture of both and, in many situations, an encapsulated droplet-in-matrix structure. 

In this ternary system, the tendency of B to encapsulate C can be considered by writing the spreading coefficient = Yca Yba Ybc- If cb positive and Age is negative, the encapsulation of B with a C layer prevails (Fig. 22.1a). On the other hand, if Xgc is positive and Acs is negative, the encapsulation of C with a B layer takes place (Fig. 22.1b). If both are negative, they will be separately dispersed as droplets in matrix A (Fig. 22.1c). 

In most cases the rubbery component forms droplets in a continuous glassy matrix and this results in a composition of enhanced toughness. Any explanation of this phenomenon needs to take into account the following facts ... 

Whilst the aliphatic nylons are generally classified as being impact resistant, they are affected by stress concentrators like sharp comers which may lead to brittle failures. Incorporation of mbbers which are not soluble in the nylons and hence form dispersions of rubber droplets in the polyamide matrix but which nevertheless can have some interaction between mbber and polyamide can be most effective. Materials described in the literature include the ethylene-propylene rubbers, ionomers (q.v.), polyurethanes, acrylates and methacrylates, ABS polymers and polyamides from dimer acid. 

Table 5 compares the tensile properties of Vectra A950 in the form of dispersed fibers and droplets in the matrix by injection molding, microfibril by extrusion and drawing [28], injection molded pure thick sample and pure thin sample, and the pure drawn strand [28]. As exhibited, our calculated fiber modulus with its average of 24 GPa is much higher than that of the thick and thin pure TLCP samples injection molded. It can be explained that in cases of pure TLCP samples the material may only be fibrillated in a very thin skin layer owing to the excellent flow behavior in comparison with that in the blends. However, this modulus value is lower than that of the extruded and drawn pure strand. This can be... 

Wood Hill (1991b) induced phase-separation in the clear glasses by heating them at temperatures above their transition temperatures. They found evidence for amorphous phase-separation (APS) prior to the formation of crystallites. Below the first exotherm, APS appeared to take place by spinodal decomposition so that the glass had an intercoimected structure (Cahn, 1961). At higher temperatures the microstructure consisted of distinct droplets in a matrix phase. 

Several methods have been used for the matrix application (1) immersing a tissue section quickly in a matrix solution, (2) spraying matrix solution onto a tissue section with an air brush, (3) putting small droplets of matrix solution onto a tissue section with an automatic pipetting device that can dispense picoliter volumes (lpL = 10 pk) of reagents.4,5,715161819... 

There may be competing factors between emulsion size and extractable surface oil that produce these results. While the finer emulsions have less extractable surface oil which should improve shelf-stability, the total surface area of the oil droplets in these powders is greater (Table V). The lower amount of surface oil provides less oil that is openly exposed to oxidation but the greater surface area of the droplets in the carrier matrix provides greater possibility for oxidation once oxygen has permeated the spray dried particles. 

Other Aluminosilicates, Transparent mullite glass-ceramics can be produced from modified binary Al C —Si02 glasses (21). In these materials, the bulk glass phase separates into tiny alumina-rich droplets in a siliceous matrix. Further heat treatment causes these droplets to crystallize to mullite spherulites less than 0.1 Jim in size. When doped with ions such as Cr3+, transparent mullite glass-ceramics can be made to absorb broadly in the visible while fluorescing in the near-ii (22,23), thereby making them potentially useful for luminescent solar collectors. 

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