密度梯度复合滤料的结构与过滤性能研究

Study on structure and filtration properties of density gradient composite filter

以聚丙烯(PP)纺粘布(简称纺粘布)为支撑层、PP熔喷布(简称熔喷布)为中间滤层、静电纺聚乳酸纳米纤维布(简称电纺布)为表面滤层,制备三级密度梯度结构复合滤料(简称三级梯度滤料),以纺黏布和熔喷布制得二级密度梯度结构复合滤料(简称二级梯度滤料),借助自动滤料测试仪等研究了滤料的结构和性能。结果表明:纺粘布、熔喷布和电纺布的纤维平均直径分别为19.58,2.89,0.71μm,平均孔径分别为76.80,12.02,2.52μm;在纤维层单位面积质量相近的情况下,随着纤维平均直径变小,滤料平均孔径变小,纤维直径和滤料平均孔径的变动幅度基本一致。三级梯度滤料的平均孔径为2.12μm,孔径分布为0.89~4.40μm;与二级梯度滤料相比,三级梯度滤料孔径范围变窄,平均孔径下降了80.5%,在气体流量为32L/min时,对空气动力学质量中值直径为0.26μm的NaCl气溶胶的过滤效率达到99.2%,过滤效率提高了66.7%,三级梯度滤料综合过滤性能得到明显提升;密度梯度滤料的阻力具有加和效应,约等于各纤维层阻力之和,密度梯度滤料的过滤效率不具有加和效应,主要取决于过滤效率最高的纤维层。

A composite filter with three-grade density gradient structure（ three-grade gradient filter for short） was prepared with polypropylene（ PP） spunbond nonwoven（ or simply ＂ the spunbond layer＂） as support layer,PP meltblown nonwoven（ or simply ＂ the meltblown layer＂） as middle filter layer and electrospun polylactic acid nanofiber fabric（ or simply ＂ the electrospun layer＂）as surface filter layer. The spunbond and meltblown nonwovens were produced into a composite filter with two-grade density gradient structure（ two-grade gradient filter for short）. The structure and properties of the filters were studied with an automatic filter tester. The results showed that the fiber average diameters of the spunbond layer,meltblown layer,and electrospun layer were 19. 58,2. 89,0. 71 μm,respectively,when the mean pore size of the layers were 76. 80,12. 02,2. 52 μm,respectively; and the average pore size of the filter was decreased at almost the same extention with the decrease of the fiber average diameter in the case of similar mass per unit area of the fiber layers; the mean pore size and the pore size distribution of the three-grade gradient filter were 2. 12 μm and 0. 89-4. 40 μm; as compared with those of two-grade gradient filter,the range of pore size of the threegrade gradient filter became narrower and the mean pore size decreased by 80. 5%; the filtration efficiency of the three-grade gradient filter reached 99. 2% for 0. 26μm NaCl aerosol in Aerodynamic mass median diameter,the filtration efficiency was greatly increased by 66. 7% and the comprehensive filtration performance was obviously improved when the gas flow rate was 32 L/min;the filtration resistance of density gradient filter was approximately equal to the sum of the resistances of each fiber layer due to the plus effect; the filtration efficiency of the density gradient filter did not have plus effect and mainly depended on the fiber layer of the highest filtration efficiency.