Polymer melt blending

For general aspects on sonochemistry the reader is referred to references [174,180], and for cavitation to references [175,186]. Cordemans [187] has briefly reviewed the use of (ultra)sound in the chemical industry. Typical applications include thermally induced polymer cross-linking, dispersion of Ti02 pigments in paints, and stabilisation of emulsions. High power ultrasonic waves allow rapid in situ copolymerisation and compatibilisation of immiscible polymer melt blends. Roberts [170] has reviewed high-intensity ultrasonics, cavitation and relevant parameters (frequency, intensity,... 

Bioceramic coatings Bone china component Polymer melt-blends Optical lenses Optical fibres Lasers... 

Polymer melt blends maybe miscible or immiscible. Miscible blends form solutions and there is no phase morphology to be of concern. Immiscible blends are characterized by two or more phases that are separated by interfaces. Most polymer blend systems are immiscible because of the low entropies of mixing associated with mixing chain-like molecules to produce homogeneous solution. 

This leads to coalescence phenomena, which are best known in salad dressing but also occur in polymer melt blends. 

Published investigations of phase morphology development in polymer melt blends in twin-screw extruders began with the work of Plochocki et al. [137] in 1988. Since 1992, several different research groups have described investigations [76,138-147]. 

In extrusion of PP/PET blends, although PET had lower t than the blends, the blends extruded at higher volumetric rates, indicating that the output was controlled either by melting or the interlayer slip. It was shown that even if the sheath-and-core monofilaments of PP/PET blends could not be oriented (because of poor adhesion between the two polymers), melt blending still produced useful oriented product. The maximum draw ratio for PET was 7, whereas for PP/PET blends it was 11. The dynamic mechanical testing of blend monofilaments, containing le(PET) = 50 and 70 wt.%, indicated that Tg(PET) remained constant and the dynamic moduli were approximately additive. 

Table 3.3 Mean Dimensions of Phases in Annealed Polymer Melt Blends...

Finally, we should motion that in addition to the geometric mean rules there have been other combining mles recommended for the cross interactions, often known as harmonic mean approaches (see Problem 3.8). These have been considered to be variations of the Owens-Wendt approach and have found some applicability especially for mixtures of polymer melts (blends) for which there are a lot of data (see Problem 15.10), also at diverse temperatures despite often being... 

Large interfacial tensions lead to coalescence of dispersed phases and coarse phase morphologies in polymer melt blends. This has been seen in various studies on the phase morphology of polyolefin-polyamide melts [63 to 66]. The coalescence phenomena observed in these systems is striking. 

There is a wide variety of both synthetic and natural crystalline fillers that are able, under specific conditions, to influence the properties of PP. In PP nanocomposites, particles are dispersed on the nano-scale. " The incorporation of one-, two- and three-dimensional nanoparticles, e.g. layered clays, nanotubes, nanofibres, metal-containing nanoparticles, carbon black, etc. is used to prepare nanocomposite fibres. However, the preparation of nanofilled fibres offers several possibilities, such as the creation of nanocomposite fibres by dispersing of nanoparticles into polymer solutions, the polymer melt blending of nanoparticles, in situ prepared nanoparticles within a polymeric substrate (e.g. PP/silica nanocomposites prepared in situ via sol-gel reaction), " the intercalative polymerization of the monomer. 

The strength of PRISM theory is its ability to accurately capture the local structural detail of polymer melts, blends, and solutions. This is most readily demonstrated by comparing the structure factor obtained from PRISM theory and scattering experiments. The partial structure factors, defined as... 

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