Droplet/matrix morphology

The phase-separated droplet/matrix morphology is an outcome of the nucleation and growth mechanism (NG) of phase separation. The phase dimensions are similar to those observed for SD, but in this case the properties are dominated by the matrix polymer with the dispersed phase playing the role of a compatlblllzed filler. A similar dispersed morphology, but with large drops, can be obtained by allowing the SD or NG system to ripen. The coarsening usually leads to a non-uniformity of properties. 

The addition of carbon black (CB) to polypropylene/epoxy (70/30) blends significantly changed the usual droplet matrix morphology in the blend (60). The... 

Even though fillers are usually introduced into polymer blends of droplet-matrix morphology, a few reports dealing with filled co-continuous blends can be found in the... 

To create a blend with a droplet matrix morphology, a prerequisite to form the elongated fibrils during the flow protocol, 1% emulsions of the caseinate-rieh phase in the alginate-rieh phase have been used. The low concentrations of the dispersed phase are ehosen to provide suflBeient transparency necessary to perform the optieal measurements. 

A second class of models directly relates flow to blend structure without the assumption of an ellipsoidal droplet shape. This description was initiated by Doi and Ohta for an equiviscous blend with equal compositions of both components [34], Coupling this method with a constraint of constant volume of the inclusions, leads again to equations for microstructural dynamics in blends with a droplet-matrix morphology [35], An alternative way to develop these microstructural theories is the use of nonequilibrium thermodynamics. This way, Grmela et al. showed that the phenomenological Maffettone-Minale model can be retrieved for a specific choice of the free energy [36], An in-depth review of the different available models for droplet dynamics can be found in the work of Minale [20]. 

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. 

Blends 3 (a,b,c) Rheologically Robust Matrix and Weak Dispersed Components Since PE 1409 is a low viscosity nearly Newtonian polymer melt, its dispersive behavior is uncomplicated and more Newtonian like. Blend 3a forms a small (3-5-pm) droplet dispersion morphology, and Blend 3b is even finer (1-2 pm), becoming, only below 2% concentration, less subject to flow-induced coalescence. The TSMEE-obtained dispersions are finer than those from the TSMEE, with a variety of kneading elements (126). What is noteworthy about these blends is the early stages of the dispersion process, shown on Fig. 11.44, obtained with Blend 3a using the TSMEE at 180°C and 120 rpm. 

Furthermore, the morphological transformation of PP/ethylene-octene copolymer blends from co-continuous to droplet-matrix reported by Lee et al. [58] at compositions close to the phase inversion (Figure 2.10) was accompanied with the appearance of a yield stress, and a higher modulus than the unfilled blend, while the ductility was maintained. 

Fig. 2.6 PCA comparing the effect of matrix morphology on the reproducibility of bacteria MALDI-mass spectral profiles. All analyses were performed with E. coli (K-12) deposited by a spray-based method (uniform matrix deposition) and two manual pipette methods dried droplet (simulating the direct transfer method) and premix (where a suspension of bacteria in matrix solution is deposited onto the MALDl plate). Ellipses represent the 95 % prediction space of the PCA clusters of replicate mass spectra for each deposition method (30 mass spectra/cluster). (See text for further details Adapted from Toh-Boyo et al. 2012, copyright American Chemical Society)...

Vinckier Inge, and Launn Hans Martin. Manifestation of phase separation processes in oscillatory shear Droplets matrix systems versus co-continuous morphologies. Rheol. Acta. 38 no. 4 (1999) 274-286. 

Figure 19.1 Schematic representations of (a) temperature-composition diagram for a partially miscible blend with a lower critical solution temperature and most common blend morphologies including (b) droplet-matrix structure, (c) fibrillar morphology, (d) cocontinuous...

In the present chapter, the morphology development of immiscible binary polymer blends is discussed. First, morphology development in droplet-matrix structures is described. Subsequently, the dynamics of fibrillar structures is reviewed and finally cocontinuous structures are briefly discussed. Although the main aspects of polymer blending are well established and polymer blends are already widely used in commercial products, recent novel insights in the areas of miniaturization and particle stabilization have opened new research topics in the area of polymer blending. In the last part of this chapter, these recent advances in polymer blend systems are briefly discussed. 

Here, A,okl1 is the total interfadal area in the material of volume V, n is the unit normal vector of the interface (cf. Figure 4), and is the dyadic of n averaged over the whole interfadal area. Equation [19] holds for blends having dther a discontinuous (droplet/matrix-typ>e) morphology or a co-continuous morphology. As dearly noted from eqn [19], Oint reflects anisotropy of the shape of the phase-separated domains. Thus, the relaxation of detects recovery of isotropic shape of the domains driven by the interfadal tension. (In this relaxed state, the interfacial tension works isotropically to balance the isotropic pressure.)... 

At the same time, it should be noted that the Palierne model, having an unsymmetrical form with respect to Gm and Gd (cf. eqn [75b]), is formulated only for the droplet/ matrix-type blends and cannot apply to blends having a co-continuous morphology at rest. Several models applicable to such co-continuous blends have been proposed. ° ° Among these models, the model proposed by Yu et can be most easily utilized for the... 

---