10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Filtration Performance of a Melt Electrospun Filter Material
DAINIUS MARTUZEVICIUS, Dalia Buivydiene, Edvinas Krugly, Darius Ciuzas, Tadas Prasauskas, Linas Kliucininkas, Kaunas University of Technology, Lithuania
Abstract Number: 812 Working Group: Materials Synthesis
Abstract INTRODUCTION. Air filtration sector continuously seeks of the development of high-durability filters, having high efficiency and low pressure drop. Nanofbrous filters, however, face issues with relatively low quality factor, since high efficiency is counter levered by high pressure drop. Melt electrospinning has emerged as an efficient technique for the formation of polymer nonwowen filtration mats. Such technique may be tuned so that the produced fibres range broadly in diameter, providing optimum efficiency with relatively low pressure drop. The presented study presents the development and testing of such filtration media.
METHODS AND MATERIALS. The prototype fibre printing apparatus was constructed by uniting principles of additive 3D printing and melt electrospinning. The apparatus consisted of movable arm holding electric heater and exchangeable nozzles combined with high voltage source to form a positively charged electrode. A spinning collector drum served as a grounded electrode.
A commercially available polymer having a relatively low viscosity and high melt flow rate (Vestamid™ L 1600, Evonik AG) was spun. During 1 hour of spinning, a mat of the area 150 cm2 with mass, depending on feed rate of polymer ranging from 26 g/m2 to 122 g/m2.
The obtained fibre mats were subjected to the air filtration tests. NaCl aerosol was generated using Collison nebulizer (Model CN 24 J, BGI Inc., USA), dried by diffusion dryer packed with silica gel, diluted with dry air and charge equalized using bi-polar neutralizer (3054A, TSI Inc.). 37 mm round sample of mats were tested, measuring upstream and downstream concentrations of particles by ELPI+ (Electrical Low Pressure Impactor, Dekati Ltd., Finland). The pressure drop before and after filtration media was measured by a pressure sensor (Model P300-5-in-D, Pace Scientific Inc., USA). Filtration efficiency (η) and Quality Factor (QF) were calculated based on the particle concentration measurements.
RESULTS. Various distributions of fibre diameters were obtained, with the mean ranging from 2.8 to 8.6 µm. By-layered structure has been achieved, with the top layer slightly more uniform with diameter modes at ≤1 µm and between 2 - 5 µm while bottom layer was a mixture of fibres with diameters ranging from 0.3 to 27.4 µm distributed in bi- or three modal manner.
The quality factor was calculated as a ratio between filtration efficiency and pressure drop with the aim to better compare manufactured filter media to off-shelf filtration materials. The calculated quality factor ranged from 0.206 Pa-1 to 0.320 Pa-1 for different mats. As a comparison, the tested commercial H13 filter material had a QF of 0.029 Pa-1. Such higher performance of the melt-spun materials may be attributed to an optimum morphology as well as lower base weight.
Further challenges to the optimization of the setup include increasing through output of the spinning. A polymer material having decreased melting temperature and increased melt flowrate as well as bearing high mechanical stability would also increase the opportunity for the expansion for this technique in air filtration sector.