Dielectric response and breakdown strength improvement of LDPE/TiO2 nanocomposites by using POSS as compatibilizing agent
In this paper, two types of nanocomposites were prepared by ball milling techniquee The first type consists of 5% untreated titanium dioxide (TiO2) incorporated into LDPE. For the second one, 5% commercial TiO2 chemically treated with trisilanol phenyl polyhedral oligomeric silsesquioxane (TSP-POSS) as dispersant was ball-milled with LDPE. The microscopic observation by Atomic Force Microscopy (AFM) showed a better dispersion into polymer matrix of the TiO2 treated with POSS as compared to untreated TiO2. It was found that LDPE/treated TiO2 nanocomposite exhibited lower relative permittivity and dielectric losses compared to LDPE/untreated TiO2. The surface treatment of LDPE/TiO2 by TSP-POSS also affects the dielectric strength. The LDPE/treated TiO2 revealed highest breakdown strength of 82 kV/mm, compared to 78 kV/mm and 71 kV/mm of LDPE neat and LDPE/untreated TiO2, respectively.
Properties of polyethylene-layered silicate nanocomposites prepared by melt intercalation with a PP-g-MA compatibilizer
Abstract Polyethylene (PE)/clay nanocomposites were synthesized by melt-intercalation using either PP-g-MA or PE-g-MA as a compatibilizer. The pristine clay was first modified with a swelling agent (octadecylamine) in solution to obtain an organophilic clay before being melt blended with a compatibilizer: PP-g-MA or PE-g-MA. Finally, these compounds were melt intercalated with PE to synthesis the PE/clay nanocomposite. The materials were characterized using X-RD, TEM, SEM, and TGA. The physical properties were observed with DMA and tension tests. Permeability tests of the PE/clay nanocomposites were also performed. The clays in PE/clay nanocomposites with the compatibilizer PP-g-MA were better exfoliated. The mechanical and gas barrier properties improved as the clay content increased.
Modeling of chemical reactors—XXIX mixing-cell model for packed bed reactors. Steady state considerations. Problems of multiplicity
Abstract The axial heat and mass transfer in tubular catalytic reactors may be described by mixing-cell model and diffusion model as well. The diffusion description yields for a strong exothermic reaction and adiabatic conditions three steady state profiles, on the other hand the mixing-cell model gives rise to more than three steady states. A simple numerical and graphical analysis for mixing-cell model is presented.