| The rapid development of industry brings economic benefits,but inevitably causes air pollution,which seriously endangers the ecological environment and human health.The use of air filter materials has become an important means to reduce air pollution.Melt-blown nonwoven material has the characteristics of large specific surface area,high porosity,adjustable permeability and simple preparation method.Now,melt-blown nonwoven material has been the main industrial air filter material.However,most of the raw materials used in the preparation of melt-blown nonwoven materials are non-renewable petroleum-based polymer materials polypropylene（PP）,and they are non-degradable after being used,which brings great burden to resources and environment.Polylactic acid（PLA）is a biodegradable thermoplastic aliphatic polyester with good biodegradability,processability and mechanical properties.At present,PLA melt-blown nonwoven material has been industrialized.However,the melt-blown nonwoven materials used only with PLA as raw materials have a single function and relatively low air filtration performance.In order to improve the air filtration performance of PLA melt-blown nonwoven material and endow it certain antibacterial properties,Ag-doped silica aerogel（SiO2-Ag aerogels）was synthesized by sol-gel method and blended with PLA.SiO2-Ag aerogels/PLA composite melt-blown nonwoven materials with different mass ratios were prepared by melt-blown processing.It is hoped that the researches in this paper may provide some theoretical references for the functional modification of PLA air filter mel-blown material.Firstly,silica（SiO2）aerogels were prepared by sol-gel method.Ethyl orthosilicate（TEOS）was used as silicon source and methyltriethoxysilane（MTES）was selected as hydrophobic modifier.Then silver nitrate（Ag NO3）was used as Ag particle source to prepare SiO2-Ag aerogels with different doping ratios by in-situ doping.By characterization and analysis,the results showed that both SiO2 aerogels and SiO2-Ag aerogels with different doping ratios had three-dimensional network porous structures.Compared with pure SiO2 aerogels,SiO2-Ag aerogels with different doping ratios included not only Si,O and C,but also Ag.FT-IR results showed that the synthesized SiO2-Ag aerogels had a Si-O-Si framework structure.After hydrophobic modification,the surface of SiO2-Ag aerogels appeared-OH and-CH3.Besides the wide diffraction peak containing SiO2 dispersion,the diffraction peak of Ag with a face-centered cubic structure also appeared in the XRD pattern of SiO2-Ag aerogels.When the molar ratio of Ag doping was 5%,the specific surface area of SiO2-Ag aerogels reached 763.04 m3/g.The antibacterial efficiencies of SiO2-Ag aerogels against Staphylococcus aureus and Escherichia coli reached 99.99%.Thus SiO2-Ag aerogels with the Ag content of 5%was selected for blending with PLA.Next,SiO2-Ag aerogels/PLA composite masterbatches with different mass ratios were prepared by the melt blending,and the structure and properties were characterized.The results showed that SiO2-Ag aerogels modified by hydrophobic modification could be uniformly distributed in the PLA matrix and had good compatibility with the PLA matrix.The content of Si and Ag in the composite masterbatch increased with the increase of SiO2-Ag aerogels content.After being blended,the chemical structure of PLA in composite masterbatch did not significantly change.When the SiO2-Ag aerogels content was 1%,the crystallinity of the composite masterbatch was the highest and reached about3.43%.With the increase of SiO2-Ag aerogels content,the thermal stability of the composite masterbatch slightly increased,while the melting index decreased.The tensile strength and elongation at break of the composite masterbatches first increased and then decreased,When the SiO2-Ag aerogels content was 1%,the tensile strength and elongation at break of the composite masterbatches reached the maximum,and increased by 55.46%and 67.86%respectively,compared with pure PLA.The composite masterbatch presented certain antibacterial properties after the addition of SiO2-Ag aerogels.Finally,the SiO2-Ag aerogels/PLA composite masterbatch with different mass ratios were prepared into the corresponding SiO2-Ag aerogels/PLA composite melt-blown nonwoven materials by the micromelt-blown machine.The structure and properties of the SiO2-Ag aerogels/PLA composite melt-blown nonwoven materials were characterized.The results showed that SiO2-Ag aerogels was evenly distributed in the interior and surface of PLA fiber in the composite melt-blown nonwoven materials.With the increasing of SiO2-Ag aerogels content,the content of Ag and Si elements in the composite melt-blown material increased,and the composite melt-blown fiber surface gradually became rough.After the addition of SiO2-Ag aerogels,the average fiber diameter and average pore size of the composite melt-blown nonwoven materials slightly increased,while the chemical structure of PLA did not change.Compared with pure PLA melt-blown nonwoven material,with the increasing of SiO2-Ag aerogels content,the glass transition temperature and melting temperature of the composite melt-blown materials increased while the crystallinity first increased and then decreased.When the SiO2-Ag aerogels content was 1%,the crystallinity of the composite melt-blown nonwoven material was the largest,about 2.84%.In addition,the filtration performance and longitudinal tensile strength of the composite melt-blown materials first increased and then decreased.When the SiO2-Ag aerogels content was 3%,the air filtration efficiency and longitudinal tensile strength of the composite melt-blown nonwoven material reached the maximum,and increased by 37.99%and 37.50%,respectively,compared with pure PLA melt-blown material.With the increase of SiO2-Ag aerogels content,the filtration resistance of the composite melt-blown nonwoven material decreased,while the air permeability and quality factors enhanced.The addition of SiO2-Ag aerogels endowed the composite melt-blown material with the certain antibacterial properties. |
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