Phase separation particle

From a manufacturing perspective, the excipients used may be very difficult to handle or process. This may lead to any number of problems during compounding, such as foaming, sedimentation, phase separation, particle flocculation, or formation of bubbles. To determine the cause of these problems, careful consideration and planning must be exercised in engineering a plant to ensure reproducible batches that can be efficiently compounded and filled. It is therefore essential that the behavior of each excipient in the formulation be well understood. 

The objectives of this test pattern is to analytically resolve these problems into three manageable segments. The first task will be to define the viscoelastic kinetic properties of a material as a function of various reaction temperatures. These properties (viscosity, viscous modulus, elastic modulus, tan delta) define the rate of change in the polymers overall reaction "character" as it will relate to article flow consolidation, phase separation particle distribution, bond line thickness and gas-liquid transport mechanics. These are the properties primarily responsible for consistent production behavior and structural properties. This test is also utilized as a quality assurance technique for incoming materials. The reaction rates are an excellent screening criteria to ensure the polymer system is "behaviorally" identical to its predecessor. The second objective is to allow modeling for effects of process variables. This will allow the material to undergo environmental... 

The achievement of enhanced toughness in a brittle polymer such as an epoxy resin is vital in applications such as adhesives, for which peel strength and resistance to interfacial debonding through crack propagation are important criteria for performance. This may be achieved by incorporation of elastomeric or other phase-separated particles into the network. These may be present before reaction or they may form during the process of... 

As a consequence of phase separation particles or domains of very small size and different refraction index appear. When they are big enough they become light scatterers and the mixture becomes cloudy in the visible range. But the size of domains plays with the wavelenght, so IR radiation can also be used to determine the onset of phase separation and characterize the growth of the nascent structures. 

Functionality can influence cure rate with epoxies. Epor terminated thermoplastics cure most rapidly other functionalities, such as hydros or amine groups cure less r dly, and those without reactive functionality cure most slowly. Functionality also influences particle size, with the largest phase separated particles being formed fiom thermoplastics without reactive functionality. Resins which are crosslinked least are more readily toughened by added thermoplastics than more highly crosslinked... 

Molecular defects as well as the real polymer morphology tend to decrease the strength. Some of these molecular, macromolecular, and morphological defects are illustrated in the schematic overview of Fig. 1.20. The right part shows macromolecular defects, such as chain ends with weak entanglements, overstressed bonds, and others, which initiate the first nanovoids and local stress concentrations. The left part illustrates morphological defects, for example, interlamellar and inter-spherulic defects in semicrystalline polymers, filler particles, and phase-separated particles in blends and composites. If the size of such defects is above a critical size, they initiate crack propagation and fracture. 

A very common way of testing emulsion stability is to age samples at various temperatures and to monitor parameters such as apparent viscosity, percentage of phase separation, particle size, zeta-potential, rheological parameters, electrical conductivity, and so forth. 

Figure 6.21. Sample of PS/PMMA blend. At left, 0 map, and at right, C. The X, Y area is 20 x 20jum the source does not state the depth, but it can be assumed that the phase-separated particles are roughly spherical, not the long streaks that they appear to be, so the Z axis is only -2pm. No correction was applied for specimen motion, which explains the shaky appearance of the Y, Z sections (lower right image of each map). (From CAMECA [364] reproduced with permission.)...

Poly(imide)/titania and poly(imide)/silica hybrids prepared using titanium triethoxide or TEOS (tetraethyl orthosilicate), respectively, were investigated by Nandi et al. (76). These systems were limited to an inorganic concentration of less than 42 wt-% and the transparency limit was well below that (-10 wt-%). Above this limit, ossly phase separated particles larger than 1 micron were observed. The hybrids of poly(imide)/titania and poly(imide)/silica showed particle sizes up to 0.1 microns... 

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