| The fuel is often mixed with impurities, moisture and other contaminants in production and transportation process. This will make the fuel pump and fuel injection nozzle of precise coincidence failure, cause oil leakage, poor atomization, deterioration of combustion, increased fuel consumption, emissions exceed the standard and black smoke. Automobile emissions directly threaten human life and health. Therefore, the successful preparation of high efficient composite fuel filter is imminent. At present, domestic vehicle filtering media are mostly filtering paper, poor in pollutant loading capacity, short life time and unefficient water filtration. However, high efficient filtration is generally imported, increase the cost sharply. Polypropylene melt-blown nonwovens has drawn great attention from the scientific research workers and industry for its light, high strength, good flexibility, corrosion resistance, good filtering performance and low cost. Preparation of composite filter was based on polypropylene melt-blown nonwovens. the solid impurities and water were removed from fuel by coalescence principle.Properties of polypropylene were analyzed in this study. The effects of collection distance screw speed, air temperature and collection time on web structure and properties were also discussed. By He plasma treatment, the surface property of polypropylene melt-blown nonwovens was improved, then acrylic monomer was grafted on the surface of polypropylene, which caused PP melt-blown nonwovens permanent hydrophilic property. Finally, a preliminary study of the forming process and its characterization of composite filtering media have been conducted.The physical properties of PP utilized in this study were as following, melting point of165.5℃. decomposition temperature of260.3℃and a melt How rate (MFR) of84g/10min. Avrami index of PP obtained by Ozavva equation varied between2.51-3.95with temperature change. Within the relative crystallinity of10%-90%. we can use Jeziorny equation to analyse non-isothermal crystallization kinetics of PP. the obtained cruves were of good linear correlation.During melt-blown process, the effects of collection distance, screw speed, air temperature and collection time on web structure and properties were discussed, and moreover, fiber diameter. thickness, surface density, pore size, air permeability and breaking force of PP nonwoven fabrics were characterized in this paper. The PP nonwoven fabrics prepared during this study had fibril diameters around4-8μm, average pore size between18-25μm, maximum pore size in the range of45-50μm. The maximum vertical break force is24.52N, while the maximum horizontal break force is9.58N, the vertical break force is always greater than the horizontal break force.The contact angle between untreated PP nonwovens and distilled water was tested to be140.9°. He plasma, in a short period of time, can make the wettability of PP nonwovens significantly improved, even the contact angle is0°. The influence of the plasma treatment on PP nonwovens and grafting conditions on the graft yield were studied in this paper. The results showed that the optimal experimental conditions:processing power100W, reaction time8.5min, monomer concentration40%, reaction temperature50℃, reaction time6h. Appropriate changes in reaction conditions could make grafting yield on the surface of PP nonwovens reached18.61μg/cm2.Treated by He plasma, a lot of new chemical bondings, C-O/C-N, C=O/O-C-O were formed on the sample. The XPS spectra showed that the untreated sample surface was mainly Cls and smaller O1s characteristic peak, at534.6ev appeared apparent Ols peak after treatment, the oxygen percent content was increased from7.84%to43.05%, carbon content was decreased from92.16%to37.02%, at402.4ev appeared weak Nls peak. These mean that after He plasma treatment oxygen-containing groups and nitrogen-containing groups were introduced on the surface of PP nonwoven fabrics. Grafted samples at1800-1600cm-1region appeared the characteristic absorption peak of ester bond, a wide medium absorption peak appeared at the3500-3000cm-1region, corresponding to the-OH stretching vibration peak. It demonstrated acrylic acid was successfully grafted onto the surface of PP non-woven fabricsIt showed that as molding pressure increasing, physical properties such as thickness, air permeability, and maximum and average pore size of resulted composite material decreased gradually. The composite material is highly effective for separating solid impurities (diameter>5μm), with filtering efficiency up to99%. The carrying capacity is about2times higher as compared with traditional filter paper. Water separation efficiencs is80.6%. further work need to be done to improve filtering efficiency for water and solid impurities w ith diameter<4μm. |
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