Morphology of the Blends

ABS domains distributed in the PC matrix in the ABS domains, rubber particles appear black and are distributed in SAN surroundings only a very weak contrast appears between PC matrix and SAN  

PC phase is dark, PMMA bright, each continuous phase incorporates dispersed particles of the other phase [2]  

Visibility of the cocontinuous morphology by volume relaxation without etching  

PC/SAN (60/40) phase structure revealed by selective swelling of one of the constituents (SAN)  

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The morphology obtained from the blend of the core-shell type microspheres and AB type block copolymers with spherical morphology is shown next [37]. Figure 12 shows the typical morphologies of the blend ob-... 

When plastics act as a physical cross-link and strength properties are indirectly related to the modulus of hard phase and morphology of the blend, the filler effect is analyzed by the following equation ... 

Such soft-touch materials are usually TP Vs or thermoplastic elastomers (TPEs) which combine the moldability of thermoplastics in the melt state with elasticity, lower hardness, fracture resistance, and surface characteristics of elastomers. However, plastics and elastomers respond differently to mechanical stress. Hence, both rheological behavior and mechanical strength will to a large extent depend on the morphology of the blend which may change with change in the composition. 

Morphology of the blends was studied by both optical microscopy and SEM. It was found that HDPE forms a continuous phase and rubber is dispersed as distinct domains. The 50 50 blend shows finer particle dispersion than other blends. In 25 75 blend both HDPE and rubber form the continuous layer. The morphology is independent of the method of preparation. 

Novel styrenic-based TPEs based on blends of a thermoplastic (polystyrene or styrene acrylonitrile) with a rubber (styrene butadiene or ethylene vinylacetate), with special reference to compatibilization and dynamic vulcanization, were reported by Patel et al. The performance properties were correlated with the interaction parameter and the phase morphology of the blend components [62]. 

When a more permeable polymer is blended with PVC, the permeability coefficient is expected to increase. The magnitude of the increase, however, will depend on the morphology of the blend. A laminar composite film containing 10% EVA would give an increase in permeability of about 10% compared with a pure PVC film (15, 18). The reported measurements for PVC with 10% EVA give an increase of about 400% (Figures 1, 2, and 3). 

The properties of immiscible polymers blends are strongly dependent on the morphology of the blend, with optimal mechanical properties only being obtained at a critical particle size for the dispersed phase. As the size of the dispersed phase is directly proportional to the interfacial tension between the components of the blend, there is much interest in interfacial tension modification. Copolymers, either preformed or formed in situ, can localize at the interface and effectively modify the interfacial tension of polymer blends. The incorporation of PDMS phases is desirable as a method to improve properties such as impact resistance, toughness, tensile strength, elongation at break, thermal stability and lubrication. 

When the modifier is a high-Tg thermoplastic, a postcure step at T > Tg M is necessary to complete the reaction in the (3-phase and to develop the final morphology of the blend. 

Measurements. The morphology of the blends was studied by optical microscopy (Leitz Dialux Pol), transmission electron microscopy (Jeol 100 U), and scanning electron microscopy (Cambridge MK II). Ultramicrotome sections were made with an LKB Ultratome III. Samples for scanning electron microscopy were obtained by fracturing sheets at low temperature. The fracture surfaces were etched with a 30% potassium hydroxide solution to hydrolyse the polycarbonate phase. Stress-relaxation and tensile stress-strain experiments were performed with an Instron testing machine equipped with a thermostatic chamber. Relaxation measurements were carried out in flexion (E > 108 dyn/cm2) or in traction (E < 108 dyn/cm2). Prior to each experiment, the samples were annealed to obtain volumetric equilibrium. 

PPy/poly(vinyl-methylketone) (PVMK) composites have been prepared using both chemical and electrochemical polymerization.72 Both PPy and PVMK are capable of forming intramolecular hydrogen bonds, as evidenced in the resultant composites. The morphologies of the blends produced using the two approaches are different, the chemically prepared material being more thermally stable. 

In the following part aspects related to morphology of the blends with and without an added compatibilizer (from the nm to the pm scale) will be presented. These include information on the interfacial characteristics (interfacial tension coefficient and thickness of the interphase), morphology, crystallization and performance of the blends. This information will be presented mainly in a tabulated form, summarizing the main feamres from the referenced publications. 

Meijer et al. [1988] and Elemans et al. [1988] investigated the potential of electron irradiation to stabilize the morphology of immiscible polymer blends. Their concept was that selective crosslinking of a dispersed phase in a matrix that remains unaffected, or degrades, should help fix the morphology of the blend. 

Since PA-6 and PA-66 are crystalline polyamides with high melting points, it is desirable to keep them as the continuous phases and ABS as the dispersed phase, for better heat and solvent resistance. The phase morphology of the blend, of course, depends upon the blend ratio and the relative viscosity of the individual components. 

Because of the high interfacial tension, the morphology of the blends is not stable. Coalescence readily occurs in the molten state. As suggested by Macosko et al. (121), in melt mixing of immiscible polymer blends, the disperse phase is first stretched into threads and then breaks into droplets, which can coalesce together into larger droplets. The balance of these processes determines the final dispersed particle sizes. With increase of disperse phase fraction (usually more than 5 wt%), the coalescence speed increases and the dispersed phase sizes increase (121-123). 

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