Blends morphology

The use of PC—ABS blends has grown significantly in the early 1990s. These blends exhibit excellent properties, particularly low temperature ductihty, reduced notch sensitivity, and ease of melt fabrication. The blend morphology (229), ABS composition, thermal history (215), PC content and molecular weight (300), processing conditions, etc, all affect the mechanical behavior of PC—ABS blends. These blends have been most frequently used in automotive and other engineering appHcations. 

Maleic modified EVA-PRP blend showed some differences in the blend morphology from unmodified EVA-PRP blend. Addition of MAH-PP significantly in-... 

Melt fracture of the extrudate was studied using M-45 wild photoautomat. Blend morphology was studied by SEM after differential solvent swelling. 

In an earlier study (44) on the effect of viscosity ratio on the morphology of PP-LCP blends we found that the viscosity ratio is a critical factor in determining the blend morphology. The most fibrillar structure was achieved when the viscosity ratio (i7lcp i7pp) ranged from about 0.5-1. At even lower viscosity ratios the fiber structure was coarser, while at viscosity ratios above unity, the LCP domains tended to be spherical or clusterlike (Fig. 1)=... 

In addition, it was found that the blends with highly fibrillar structure exhibited a significantly lowered viscosity. Increased shear rate caused slight changes in the blend morphology but did not enhance the fiber formation. Thus, in addition to shear, elongational forces are needed to achieve a well-fibrillated blend structure and significant mechanical reinforcement. 

In manufacturing and processing polymer blends, it is thus important that the viscosity ratio be within the optimal range in the actual processing conditions. Not only the polymers to be blended but also the temperature and processing conditions (shear, elongation) should be carefully selected. Other factors, such as interfacial tension [46,47] and elasticity of the blended polymers, may also influence the blend morphology. 

At lower temperatures (180-200°C) the material was processed without melting the LCP and a real composite structure with solid LCP fibers in the PP matrix was formed. When processing was done above the Tm of the LCP (280°C), all the material was molten during processing and a compositelike blend morphology was created in situ during cooling of the oriented melt phase. 

The composite and blend morphologies were nevertheless different in the solid state. In the composite there... 

P. M. Subramaniam, Polymer Blends Morphology and Solvent Barriers, ACS, Washington (1990). 

During a steady-state capillary flow, several shear-induced effects emerge on blend morphology [4-6]. It is, for instance, frequently observed that TLCP domains form a fibrillar structure. The higher the shear rate, the higher the aspect ratio of the TLCP fibrils [7]. It is even possible that fibers coalesce to form platelet or interlayers. 

Ghosh, A. and De, S.K. Dependence of Physical Properties and Processing Behavior of Blends of Silicone Rubber and Fluorombber on Blend Morphology. Rubber Chem. Technol. 77(5), 856-872, November/December 2004. 

Galuska, A.A., Poulter, R.R., and McElrath, K.O., Eorce modulation AEM of elastomer blends Morphology, fillers and cross-hnking. Surf. Interface Anal., 25, 418, 1997. 

TPEs from thermoplastics-mbber blends are materials having the characteristics of thermoplastics at processing temperature and that of elastomers at service temperature. This unique combination of properties of vulcanized mbber and the easy processability of thermoplastics bridges the gap between conventional elastomers and thermoplastics. Cross-linking of the mbber phase by dynamic vulcanization improves the properties of the TPE. The key factor that controls the properties of TPE is the blend morphology. It is essential that in a continuous plastic phase, the mbber phase should be dispersed uniformly, and the finer the dispersed phase the better are the properties. A number of TPEs from dynamically vulcanized mbber-plastic blends have been developed by Bhowmick and coworkers [98-102]. 

Huneault, M. A., Shi, Z. H., and Utracki, L. A., Development of polymer blend morphology during compounding in a twin-screw extruder. Part IV A new computational model with coalescence. Polym. Eng. Sci. 35(1), 115-127 (1995). 

Sundaraj, U., Dori, Y., and Macosko, C. W., Sheet formation in immiscible polymer blends model experiments on an initial blend morphology. Polymer 36,1957-1968 (1995). Swanson, P. D., and Ottino, J. M., A comparative computational and experimental study of chaotic mixing of viscous fluids, J. Fluid Mech. 213, 227-249 (1990). 

Electron microscopy, 16 464, 487-495 history of, 16 487-488 in polymer blend morphology determination, 20 339-340 of PVC particles, 25 658-659 of silica, 22 371-372 in surface and interface imaging, 24 75-80... 

Table 18. Influence of the films composition and of the blend morphology on the films permeability to 02 [295]...

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