ساناز بابادی

Polymers are widely used in different industries because of their wide range of applications. The use of polymer combinations as blends is common because one single polymer alone does not provide the desired properties required for some specific applications. There are two methods for preparation of polymer combinations: chemical (copolymerization) and physical (blending). Polymer combination leads to better performance, physical and mechanical properties while it reduces the cost effectively. Mixing of polymers is usually difficult because the entropy of mixing is low, and induces phase separation in polymer blend. The properties of polymer blends are affected through phase separation. The properties of polymer blends are associated with their morphology and affected by the miscibility of components and phase separation mechanism. Phase separation in polymer blends can be explained by a combination of kinetic and thermodynamic effects. The physical origin of phase separation is due to fluctuations that include different mechanisms such as nucleation, diffusion, growth and coalescence. So it is of utmost importance to know the governing mechanisms and the factors affecting the phase separation. There are many ways to identify this phenomenon, among them the rheological measurements are the best. This article provides a comprehensive view of the field of phase separation in the polymer blends, the dominant mechanisms, the effective parameters and the methods of determining the phenomenon.

One of the most common methods to removed contaminations from different substrates is to use the photocatalysis properties of a thin TiO2 nanoparticles coating on that substrate. A thin layer of TiO2 nanoparticles are usually applied on any surface using the Solgel method. Polyester fabrics were modified with TiO2 and TiO2/SiO2 nanocomposites through a low-temperature sol–gel method, so the self-clean properties of TiO2/SiO2 hybrid coatings on polyester fibers were studied. Silica was used to reduce the tendering effect of TiO2 nanoparticles. Sol-gels from TiO2, SiO2, and their blends in different weight ratios of 20:80, 50:50 and 80:20 were prepared and coated on the fibers surfaces by immersion, padding, and curing. FTIR and ATR results confirm the appearance of TiO2 and SiO2 nanoparticles in the solgels adnd chemical bonds between the coating and fibers after the deposition of the TiO2/SiO2 solgels. XRD experiment revealed that the nano silica treatment only influenced the surface properties of TiO2 nanoparticles and not the morphology and crystalline structure. Surface morphology of polyester samples was analyzed through the SEM images and it is shown that adding SiO2 resulted in a more uniform coating with a higher thickness. Contact angle measurements showed higher hydrophilicity by increasing nano SiO2 content. The highest self-clean property under UV radiation was also seen for the 50:50 SiO2/TiO2 composition. Finally, the mechanical properties of coated fibers dropped under UV radiation and it is shown that SiO2 incorporation in the coating formulation resulted in a slower rate of decrease in mechanical properties upon UV radiation.