Papers by Keyword: Polyimide Membrane

Abstract: Polyimide membrane pervaporation was introduced to separate the costly diene mixtures of cyclopentadiene/methylcyclopentadiene (CPD/MCPD) from cracking C5 fractions. Four kinds of membrane solutions were prepared and two kinds of polyimide homogenous membranes were fabricated by thermal imidizations using the dianhydrides (BPADAand PMDA) and the diamines (ODA and DDS). The effect of the casting solutions viscosity on the membrane formation was revealed, and the formation of functional groups and the synthesis mechanisms of the thermal imidizations were indicated by FT-IR. The adsorption behaviors and the pervaporation performances were studies for BPADA-ODA and PMDA-ODA membranes. The results show that the permeation fluxes are 164g∙m^-2∙h^-1 and 4.2g∙m^-2∙h^-1 for BPADA-ODA and PMDA-ODA membranes respectively, while the separation factor are 1.93 and 8.9 for these two membranes respectively. 88.5 wt% concentration of MCPD was achieved in the circulated feed side ultimately.

Abstract: Tannery deliming-bating wastewater contains lots of pollutants including ammonium salt, interfibrillary substances and residual enzymes. In order to reduce the pollution, the wastewater was purified by ultrafiltration with polyimide membrane and recycled in deliming-bating process. Solutes in the wastewater were evaluated by COD, total nitrogen and suspended substance. The effects of ultrafiltration parameters on permeate flux and solute rejections were investigated, and the characteristics of wastewater, as well as membrane cleaning were measured during the recycling. The results show that a steady permeate flux of over 31.5L/m²h with rejections to COD of above 89% and total nitrogen of above 82% can be obtained at 25°C under 0.090MPa in pH7.5 during the ultrafiltration. In the repeated recycling, neither the organic substances nor the nitrogenous substances could be accumulated in operation liquor. The recycling process has the same deliming-bating effect as conventional process. It has good potential for industrial application.

Abstract: The advantages of micromachining over conventional fabrication include precise dimensional control, integration of on-chip circuits and potential low cost owning to batch processing. Fabrication microspeaker for hearing instrument application using MEMS technology is challenging because of certain critical requirements, including their small size, low driving voltage, high output sound pressure level, flat frequency response and low energy consumption. A small in size, lightweight, and low cost microspeaker is demanded for application such as cellular phones and hearing aids. The device consist of two part; first parts is a micromachined polyimide membrane as the sound generating plate, where thevoice coil placed on the top of membrane, and the coil is a single loop voice coil. The second part is back plate permanent magnet. The disc permanent magnet bonded on acoustic hole plate is Neodymium-Iron-Boron (NdFeB) with magnetization of 1.45 T, diameter 1.6 mm, and thickness 0.8 mm. The fabrication process and performance of the first result device is discussed, and the thickness of electroplated single loop voice coil copper 10 mm and acoustic hole bonded together. The total size of the microspeaker chip is 5 mm x 5 mm x 1.5 mm, polyimide membrane thickness 2 mm.