Melt-blending advantages

The miscibility between polyarylate and PET may be further driven by transesterification reaction within the melt phase, which occurs slowly at T 280°C but more rapidly at T > 300°C [Robeson, 1985 Eguiazabal et al., 1991]. In any case, polyarylate can readily form transparent blends when the PET content is 30% and the melt blending done above 300°C. Hence by adjusting the melt blending conditions, PET can be used to lower the cost and improve the chemical resistance of polyarylate while maintaining an adequate level of transparency. The heat distortion temperature is, of course, sacrificed to some extent. Except for some improved chemical resistance, processability and cost the blend does not seem to offer any compelling advantages over polyarylate and hence its applications appear to be quite limited. 

The above selective cross-linking of acrylate rubbers in a polyamide thermoplastic matrix leads to a PA-acrylate rubber-blend TPV with the melt-processing advantages of the PA and the high-performance properties of a thermoset acrylate rubber. The PA matrix provides the high heat resistance and solvent resistance while the cross-linked polyacrylate provides the rubber elasticity coupled with its own excellent weatherabdity and oil resistance properties to the TPV. 

Abstract Semiconductor nanoparticles have attracted much attention due to their unique size and properties. Semiconductor-polymer hybrid materials are of great importance in the field of nanoscience as they combine the advantageous properties of polymers with the unique size-tunable optical, electronic, catalytic and other properties of semiconductor nanoparticles. Due to combination of the unique properties of organic and inorganic components in one material, these semiconductor-polymer hybrids find application in environmental, optoelectronic, biomedical and various other fields. A number of methods are available for the synthesis of semiconductor-polymer hybrid materials. Two methods, i.e. melt blending and in-situ polymerization, are widely used for the synthesis of semiconductor-polymer nanocomposites. The first part of this review article deals with the synthesis, properties and applications of semiconductor nanoparticles. The second part deals with the synthesis of semiconductor-polymer nanocomposites by melt blending and in-situ polymerization. The properties and some applications of semiconductor-polymer nanocomposites are also discussed. 

It has been well recognized that melt blending of a thermotropic liquid crystalline polymer (LCP) and an isotropic polymer produces a composite in which fibrous LCP domains dispersed within the blend act as a reinforcement il ). The so-called insitu composite possesses several advantages in comparison with the inorganic reinforced thermoplastic composites. Firstly, LCP lowers the blend viscosity in the actual fabrication temperature range (3-5), Hence, the enhanced processability endows moldability for fine and complex shaped products. 

Thus, melt blending method of nanocomposites preparation is a common alternative, and is particularly useful for thermoplastics processing. This method is based on high temperatures and shear to disperse nanoparticles on the polymer matrix, and has advantages as its speed and simplicity, besides being the most compatible with currently industrial processes, among which, extrasion is the most practiced (Coleman et al. 2006a, b Esawi et al. 2010 Lee et al. 2005 Moniruzzaman and Winey 2006). 

Polymer—GO nanocomposites are mainly produced by three methods in situ polymerization, solvent processing, and melt blending. A comparative study showed that melt blending composites presents a fine balance between mechanical and electrical properties with the advantages of the process being cost-effective and environmentally friendly compared to in situ polymerization and solvent processing (Senguptaa et al., 2010). 

The direct melt blending process display the great advantage of processing ease but the major drawback is the sometimes-observed difficulty to intercalate preformed long polymer chains in clays displaying a poor compatibility with the matrix. Thus, the easier intercalation of the monomer could be used as the first step of an alternative process followed by the in-situ polymerization of the monomer in between the silicate platelets. 

The morphological characterization of the composites has been performed by both XRD and TEM. The XRD patterns of Cloisite Na based materials show an increase of the interlayer spacing from about 1.2 nm (in the native clay) to 1.6 nm for the in-situ polymerized nanocomposites, attesting for the formation of an intercalated structure. Thus, it comes out that in-situ polymerization of e-CL allows to prepare intercalated nanocomposites from non-modified clay. This is a major advantage of this process since it has been observed that the direct melt blending of preformed PCL chains with the same Cloisite Na only leads to conventional microcomposites (without any intercalation). 

The WAXS and TEM evaluations indicated an intercalated montmor-illonite dispersion. The melt-blending step produced the best orientation of the montmorillonite. Extrusion resulted in a return to a random distribution of the intercalated montmorillonite particles. The increase in tensile modulus was modest (the authors now adopt GPa units instead of ksi). The tensile modulus of the melt-blended composite was higher (2.7 GPa for the pure polymer increased to 3.0 GPa for the 3% montmorillonite). The extruded polymer composite was evaluated as fibers. No mechanical performance advantages were measured for the extruded composite (2.1 GPa for the pure polymer increased to 2.4 GPa for the composite). 

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