Objective At present, the problem of air pollution is becoming increasingly serious. Melt-blown nonwovens have the characteristics of fine fibers, high porosity, and small pore size, which can effectively filter out dust and ensure the health of the wearer. Most of the commercially available melt-blown nonwovens are made from polypropylene (P P) due to their excellent filtration performance, but their non-renewable and non-degradable nature of the materials themselves may lead to resource crises and environmental pollution issues. Therefore, the development of green and renewable melt-blown nonwovens is of great significance. Method Different types of electrets and polylactic acid (P L A) were selected to prepare PLA/electret composites by melt blending and hot pressing, in order to obtain the best electret SiO2 for PLA. Next, the SiO2 was modified by silane coupling agent KH570 to reduce its agglomeration. As the last step, PLA/SiO2 melt-blown nonwovens were prepared by melt-blown spinning and high pressure in-situ electret technology, and charge storage capacity and air filtration performance of the samples were systematically investigated. Result The PLA/electret composite membrane material was successfully prepared using the melt blending method. The PLA/SiO2 membrane material showed an increase in peak intensity at 1109 cm, which is the symmetric stretching vibration peak of Si-O of SiO2, proving the successful composite (Fig. 2). The starting thermal decomposition temperature of the PLA/polytetrafluoroethylene (PTFE) membrane material is reduced to around 240 °C and the starting thermal decomposition temperature of the P L A/SiO2 membrane material is set at around 302 °C, demonstrating that the addition of the electret SiO2 has little effect on the thermal stability of PLA (Fig. 3). The electret significantly improves the charge storage capacity of the PLA membrane material, where the surface electrostatic charge is 8.154 kV for the pure PLA membrane material and 17.44 kV for the P L A/SiO2 membrane material, an increment of up to 113.88 % (Fig. 3). The residual electrostatic charge on the surface of the PLA membrane material was 3.23 kV after 48 h, while the residual electrostatic charge on the surface of the P L A/SiO2 membrane material was still as high as 6.34 kV. This demonstrates that the addition of a 1% mass fraction of SiO2 nanoparticles resulted in a better electret effect on the PLA membrane materials. In order to reduce the agglomeration of SiO2, the silane coupling agent KH570 was used to modify the SiO2. The modified SiO2-570 sample shows a C-H vibration peak at a wavelength of 2930 cm-1 and a weak C=U stretching vibration peak at 720 cm-1, both of which are characteristic peaks of KH570 Both of them are characteristic peaks of KH570, which proves that KH570 was successfully grafted onto the SiO2 surface (Fig. 5). The modified SiO2 - 570 nanoparticles are more uniformly dispersed in the PLA matrix, effectively reducing the agglomeration of SiO2 (Fig.6). The air filtration efficiency of the PLA melt-blown nonwovens was only 37.5% at a gas flow rate of 32 L/min (Fig.8). The filtration performance of the PLA/SiO2-570 melt-blown nonwovens was superior, with a significant increase in filtration efficiency to 88.4% and a filtration resistance of only 6.2 Pa, making it more valuable for practical applications. Conclusions Firstly, PLA/PTFE, PLA/tourmaline and PLA/SiO2 composite membrane materials were prepared by melt blending method. Among them, the electret SiO2 has less influence on the thermal stability of PLA, and the prepared composite membrane materials have a high surface charge and relatively slow charge decay. Secondly, in order to reduce the agglomeration of SiO2, the silane coupling agent KH570 was successfully grafted onto the SiO2 surface, and the SiO2 - 570 nanoparticles were more uniformly dispersed in the PLA matrix, significantly reducing the agglomeration of SiO2. Finally, the PLA/SiO2-570 melt-blown nonwovens prepared by melt-blown spinning processing and in situ electret technology has excellent filtration performance, with a significant increase in filtration efficiency to 88.4% and a filtration resistance of only 6.2 Pa. It has great potential for applications in personal protection and air filtration. © 2023 China Textile Engineering Society. All rights reserved.
