【作者】 刘亚；

【导师】 成国祥； 程博闻；

【作者基本信息】 天津大学 ， 材料学， 2009， 博士

【摘要】 本文采用可生物降解的聚乳酸(PLA)为原料,利用熔喷法非织造技术制备熔喷非织造布(MB),再通过静电纺技术将其喷覆在熔喷非织造布上制备熔喷/静电纺复合法PLA非织造布(PLA MB/ES Nw)并用于过滤材料;该方法替代熔喷的驻极过程,在相同定量的基础上可以大大提高熔喷非织造布的过滤效率,而过滤阻力增长不大,生产工艺简单,能耗小,成本低,可用于过滤空气中的微粒且效果显著。本文首先通过调节热空气喷吹温度、速度、狭缝宽度、接收距离(DCD)等工艺参数,系统地研究了PLA熔喷非织造布(PLA MB)生产工艺参数与其结构和性能的关系。结果表明,随着热空气温度升高,产品的过滤性能有所降低,而透气性能增加;随着热空气狭缝宽度的增加,产品的过滤效率降低,透气性能增大;随着DCD的增加,产品的过滤效率增大,而透气量也增大,且基本与DCD成正比变化。由于工艺参数存在交互作用,本文进一步采用三层后向传播学习方法(BP)的神经网络模型处理实验数据并进行性能预测,结果表明,BP神经网络模型预测的过滤效率平均值误差在±3%以内,透气量平均值的误差在±8%以内,为优化生产工艺参数提供了一定的理论基础。在成功制备PLA MB的基础上,本文重点研究了PLA MB/ES Nws的制备技术。选用1,4-二氧六环/丙酮作为PLA的共混溶剂制作静电纺丝液,且当纺丝液浓度为8%、纺丝的过程中加入少量的NaCl时,纺出纤维的性能较好。在静电喷覆时间为10min时,所得PLA MB/ES Nws过滤材料的过滤效率和透气量的综合效果较好。根据所制备的PLA MB/ES Nws,本文又进一步建立了复合非织造布的结构模型,并对结构参数与工艺条件的关系进行了分析。通过调节电压、挤出速率和接收距离等工艺参数,本文又研究了静电复合工艺参数对PLA MB/ES Nws的结构与性能的影响。结果表明,随着静电纺电压的提高,纤维直径逐渐变细,PLA MB/ES Nws的过滤效率增大,透气性能下降;随着纺丝液挤出速率的增大,纤维的平均直径增大,PLA MB/ES Nws的过滤效率先降低后增大,透气量增加;随着接收距离的增大,纤维直径逐渐变细,且线密度的均匀度增加,PLA MB/ES Nws的过滤效率增大,透气量降低。同时,还进一步在上述结构模型基础上,建立了用于表征过滤性能的过滤模型,并分析了过滤参数及不同层次结构参数对过滤性能的影响。本文还采用三层BP神经网络模型分两步训练处理实验数据并进行复合工艺参数预测。结果表明,BP神经网络模型预测的过滤效率误差在±0.5%以内,透气量的误差在±2%以内,预测结果与实际用于表征产品性能的平均值之间的误差非常小,为优化工艺参数制备高效PLA MB/ES Nws过滤材料提供了依据。更多还原

【Abstract】 Poly (lactic acid) (PLA) is an excellent biodegradable material. Through nonwovens technology it is made into meltblowns (MB). Then through electro-spinning (ES) technology the electro-spinning fibers are spun onto the MB to produce PLA MB/ES bi-layer nonwovens (MB/ES Nws) and it is used for filtrations. Using ES technology instead of electret process, the PLA MB/ES Nws exhibits better filtration performance than MB in the same GSM and its filtration resistance remains unchanged. The produce process of PLA MB/ES Mws is simple and less energy costs during its producing, so the cost is low. It exhibits excellent particle separation performance during the air filtration process.Through adjusting the production parameters, such as hot air temperature, velocity, the width of air gap and die to collector distance (DCD), the relationship between the PLA MB technical parameters and its structure and performance is studied systemic in the paper. The results show that with the increase of hot air temperature, the filtration efficiency of the meltblowns decreases a little and air permeability increases. With the increase of the width of air gap, the filtration efficiency of the meltblowns decreases and air permeability increases. With the increase of DCD, the filtration efficiency and air permeability increases, and it changes linearly according to DCD. Because the interaction of the technical parameters, a three-layer back-propagation (BP) neural network model is further adopted to deal with the experimental data and forecast its performance. The results show that the average error of filtration efficiency forecasted is less than±3%, the average error of air permeability forecasted is less than±8%. It provides the academic foundation of optimizing the production parameters.On the base of successful preparation of PLA MB, it is mainly studied preparation technology of PLA MB/ES Nws in this papaer. The performance of ES fibers are better when the mixed solvent of 1,4- dioxane/acetone is adapted and the PLA quality concentration is 8% with a small quantity of NaCl in the spinning solution. After 10 minutes for electro-spinning, the integrated performance of filtration efficiency and air permeability of MB/ES PLA Nws is better. According to the prepared PLA MB/ES Nws, a structure model is further established and the relationship between the structure parameters and the process condition is also analyzed in this paper.Through adjusting the production parameters, such as voltage, extrude velocity and die to collector distance (DCD), the relationship between the electro-spinning technical parameters and its structure and performance is studied systemic in the paper. The results show that with the increase of voltage, the fiber diameter turns fine and the filtration efficiency of the PLA MB/ES Nws increases but air permeability decreases. With the increase of the extrude velocity, the average fiber diameter increases and the filtration efficiency of the PLA MB/ES Nws decreases first then increases, and its air permeability increases. With the increase of DCD, the fiber diameter turns fine and becomes uniform. As a result the filtration efficiency of the PLA MB/ES Nws increases and air permeability decreases. On the base of the structure model established before, a filtration model is further established to elaborate the filtration property of PLA MB/ES Nws in this paper. And the filtration parameters and different structure parameters which influenced the filtration property are analyzed in this paper.A three-layer BP neural network model with two-step training is adopted to deal with the experimental data and forecast the compound technical parameters of PLA MB/ES Nws. The results show that the average error of filtration efficiency forecasted is less than±0.5%, the average error of air permeability forecasted is less than±2%. It provides the foundation of producing high performance PLA MB/ES Nws filtration materials.更多还原