聚乙烯三氟氯乙烯熔喷非织造材料的制备及其过滤性能

为制备耐高温熔喷过滤材料以应对高温工业粉尘的污染问题，研究了聚乙烯三氟氯乙烯(ECTFE)的热性能、动态热机械性能、流变性能以及形貌，并选取合适的工艺参数成功制备得到ECTFE熔喷非织造材料，对ECTFE熔喷非织造材料的结构与高温处理下的过滤性能进行表征，结果表明：ECTFE熔喷非织造材料纤维网中的纤维呈现随机交错、缠绕排列，其纤维直径分布在4～12μm,平均直径约为7.12μm,其孔径主要分布在45～55μm;当将ECTFE熔喷非织造材料从150℃预加热到210℃并用于过滤后，其对PM₁₀的过滤效率均保持在99.96%,而对PM_2.5和PM₅的过滤效率随着ECTFE熔喷非织造材料预加热温度的升高逐渐降低，但仍能够保持在55.16%以上。

Preparation and filtration properties of polyethylene trifluoroethylene melt-blown nonwovens

Objective In order to prepare high temperature resistant melt-blown filter materials to deal with the pollution of high temperature industrial dust, the thermal properties, dynamic thermomechanical properties, rheological properties and morphology of polyethylene trifluoroethylene (ECTFE) masterbatch were studied at first, and then the ECTFE melt-blown nonwovens were to be prepared by selecting appropriate process parameters. So far, there are few studies on ECTFE melt-blown nonwovens for air filtration.Method The properties and structures of ECTFE masterbatch were determined by differential scanning calorimeter, dynamic thermo mechanical analyzer, thermogravimetric analyzer and melt flow meter. The ECTFE melt-blown nonwovens were then successfully prepared according to these studies on ECTFE masterbatch. The surface morphologies and pore size distribution of ECTFE melt-blown nonwovens were scrutinized by scanning electron microscope and pore size meter. The ECTFE melt-blown nonwovens was preheated at different tempera-tures (150, 170, 190, 210 and 220 ℃) using a muffle furnace. After that, the filtration efficiency and tensile properties of ECTFE melt-blown nonwovens was calculated by the dust particle detector and universal tensile tester.Results The results show that with the increase of heating rate, the melting peak(T_p) of ECTFE masterbatch shifted to the right, and T_p was enhanced from 235.02 to 239.21 ℃, and the width of half peak increased(Fig. 3). The glass transition temperature of ECTFE masterbatch was found to be about 86.2 ℃(Fig. 4). The decomposition temperatures at initial and 5% weight lost were 300 and 372 ℃, respectively. It is obvious that for ECTFE masterbatch the temperature of the thermogravimetric zone was obviously higher than that of the melting process, which ensures the smooth process of ECTFE melt-blown nonwovens. When the test temperature increased from 250 to 290 ℃, the melt flow index elevated from 180 g/(10 min) to 376 g/(10 min), indicating that the melt fluidity of ECTFE masterbatch became better with the increasing of the temperature(Fig. 6(a)). The diameter of the fibers in ECTFE melt-blown nonwovens ranged from 4 to 12 μm, and its average diameter was about 7.12 μm. Additionally, the pore size of ECTFE melt-blown nonwovens was mainly in the range from 45 to 55 μm(as shown in Fig. 7). The filtration efficiency of ECTFE melt-blown nonwovens for PM₁₀ was maintained at 99.96% after it was preheated at temperatures of 150~210 ℃. Although the filtration efficiency of ECTFE melt-blown nonwovens for PM_2.5 and PM₅ decreased slightly with the increasing of preheated temperatures, it still exceeded 55.16% and 72.93%, respectively(Fig. 8).Conclusion The glass transition temperature and melting peak of ECTFE masterbatch were about 86.20 and 235.02 ℃, respectively. Its complex viscosity decreased when increasing the shear rate and the ECTFE was categorized as a "pseudoplastic fluid". Besides, ECTFE masterbatch has excellent thermal stability at constant temperatures of 260, 270 and 280 ℃. ECTFE melt-blown nonwovens can be successfully fabricated under the conditions of heating temperature 260 ℃, hot air temperature 260 ℃, airway pressure 0.2 MPa, melt-blown pressure 0.5 MPa, acceptance distance 13 cm and translation speed 0.1 mm/s. The fibers in the ECTFE melt-blown nonwovens web were randomly interleaved and wound, and ensures that the ECTFE melt-blown nonwovens with high filtration efficiency. Therefore, it is believed that ECTFE melt-blown nonwoven should be an ideal filter material for high temperature resistant air filtration.