Optical Study Of Polymer Dispersed Mixed Liquid Crystals
Recently, Liquid Crystal (LC) dispersed with polymer is used to enhance the physical properties of the LCs materials. These materials possess combined application of LC and polymer and their electro-optic applications have been extensively studied during last decades. The LC mixture consists of Nematic and Cholestric that are dispersed in a monomer or prepolymer with different concentration. The existing Polymer Dispersed Liquid Crystal (PDLC) consists of different concentrations of LC and monomer. The textures and Phase transition temperature (PTTs) can be studied by Polarising Microscope Studies (PMS). The Phase transition temperature (PTTs) can also be studied by Fabry-Perot etalon Scattering Studies (FPSS) In this paper, we present the changes in transition temperature along with new phase transition temperature in PDLC. Measurements were performed for both heating and cooling of various samples. In addition to this, Refractive Index (RI) of all samples were found for optical characterization of the material. Texture observation and spectroscopic techniques are used to characterize the other properties of the PDLC samples. The PDLC suspension can be used as a new liquid crystalline material that does not require any additional alignment processing or treatment. Our results will provide new opportunity and their uses in advanced technology development.
Effect of Light on Nematic Liquid Crystal
Liquid Crystal is a phase formed between a crystal and a liquid with a degree of order intermediate between the molecular disorder of liquid and the regular structure of crystal..The optical properties of Liquid Crystals are one of the most interesting and certainly the most beautiful features of the phase. In this paper we studied the properties of light as it propagates through a sample of Nematic Liquid Crystals. Amongst various properties of light; we studied polarization and scattering of light through Nematic Liquid Crystals. Liquid crystal materials generally have several common characteristics. One of the characteristics is the transition temperature which will be measured over temperature range of phases. In present work we studied Cholesteryl Oleate. The results are analyzed with the help Polarizing microscopy (PMS) and Spectroscopic technique using Fabery —Perot Etalon. The phase transition of liquid crystal between various mesomorphic forms occurs at a thermodynamically defined temperature as ...
EFFECT OF SAMPLE PREPARATION ON WATER TREE RESISTANCE OF XLPE/SEBS BLENDS
The effects of an aromatic polymer, such as poly[styrene-b-(ethylene-co-butylene)b-styrene] (SEBS), and its preparation processes on water tree resistance, morphology, crystallinity, dielectric constant and dielectric loss tangent of crosslinked polyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA) blends were investigated. The XLPE/SEBS samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, dielectric spectral analysis and the accelerated water treeing experiment. The results clearly showed that although SEBS was partially compatible with LDPE and it was dispersed evenly in XLPE matrix, the blends demonstrated excellent dielectric performances, such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBS blends was decreased with increase in SEBS content and it was further decreased with the addition of EVA. SEBS could effectively improve the water-tree resistance of XLPE and both SEBS and EVA were found to improve the water tree resistance of XLPE synergistically as expected. The differences in sample preparation processes could change the phase morphology and dielectric performance of the blends, and could also influence the dispersion of SEBS in XLPE matrix as well as the crystallinity of the blends. Different preparation processes led to different water tree resistance behaviours of the samples. The improvement of SEBS dispersion in XLPE matrix helped to improve the water tree resistance of XLPE.