Preparation And Characterization Of Evoh,PP/Evoh And Evoh/Pet Nanofiber Membranes

Because of specific properties of large surface area, large draw ratio, good biocompatibility, and low fluid resistance, nanofibers have found application in many areas, such as improving filtration efficiency of membrane devices, increasing protective and comfort performance of chemical and biological protective clothing. Therefore, the nanofiber membranes have many good performances, such as high porosity, large specific surface area, low weight, pore interconnevtivity, small pore size, pore size distribution and so on.In this study, ethylene vinyl alcohol (EVOH) nanofibers were prepared from EVOH/cellulose acetate butyrate (CAB) immiscible polymer blends by in situ microfibrillar formation during the melt extruding process. The EVOH nanofiber membranes were prepared by wet-laid process. The surface morphology, crystallization properties of EVOH nanofibers and surface morphology, mechanical properties, porosity, specific surface area, pore size and pore size distribution of EVOH nanofiber membranes were analyzed. The results showed that the average diameter of EVOH nanofibers could be controlled in the range of162-260nm. The pore size of EVOH nanofiber membranes was related to nanofiber diameter. The porosity, mechanical properties and of EVOH nanofiber membranes increased, while the specific surface area of EVOH nanofiber membranes decreased with the increasing of EVOH nanofiber diameter, respectively.The PP/EVOH nanofiber membranes were also prepared via wet-laid process. The properties of nanofiber membranes including the surface morphology, apparent density, porosity, contact-angle, pore size distribution, specific surface area, water flux and filtration were investigated. The result showed that porosity, water contact-angle, pore size and pore size distribution of PP/EVOH nanofiber membranes were bigger than EVOH nanofiber membranes. The water flux of PP/EVOH nanofiber membranes decreased with the increasing of testing time. After the heat-treatment, the pore size, porosity and water flux of PP/EVOH (30/70) nanofiber membranes decreased slightly, which were unfavorable for the applications of nanofiber membranes. Therefore, considering all the properties of nanofiber membranes, we chose the PP/EVOH (30/70) nanofiber membranes as the most favorite one, which could be used in filtration field. The rejection rate of TiO2suspension by the PP/EVOH (30/70) membranes was above95%. The nanofiber membranes resistance increased with the increasing of permeation time, and most of the membrane resistance came from the pore blocking and adsorption.Finally, the EVOH/PET nanofiber membranes were prepared by the same way of laid-wet process. The morphology, porosiry, pore size, specific area, mechanical property, water flux and filtration resistance of EVOH/PET nanofiber membranes were studied.The EVOH/PET nanofibers could be dispersed in water very well with the increasing of EVOH nanofiber. The porosity and mechanical properties of EVOH/PET nanofiber membranes were increased because of the increasing number of EVOH nanofibers. While the pore size of EVOH/PET nanofiber membranes became smaller. After the heat-treatment, the mechanical properties of EVOH/PET (30/70) nanofiber membranes increased slightly, while the porosity and water flux had little change. So the heat-treated EVOH/PET (30/70) nanofiber membranes were used to filtration field. The rejection rate of TiO2suspension by the heat-treated EVOH/PET (30/70) membrane was above90%. The heat-treated EVOH/PET (30/70) nanofiber membranes resistance increased with the increasing of permeation time. The EVOH/PET nanofiber membranes resistance came from the resistance of adsorption and pore blocking as well as the resistance of membrane itself, which was the main reason why seepage flux decreased.