Studies On Functional Modification And Properties Of Fibers And Nonwovens

Modified nonwovens have a wide range of applications due to the special functions.With the development of science and technology,there are a variety of methods to prepare modified nonwovens,including profile modification,compound modification,blend modification,graft modification,surface treatment modification,etc.Various modified nonwovens with different functions have been prepared by these methods.In this paper,a modified ultra-fine polypropylene nonwoven fabric was prepared by a novel electrostatic-assisted melt blown process;a poly(m-phenylene isophthalamide)/polyacrylonitrile multi-walled carbon nanotube(PMIA/PANMWCNT)composite nanofiber membrane was fabricated using electrospinning;amphoteric cotton nonwovens were prepared by atmospheric pressure plasma treatment.The properties and applications of the modified nonwovens were studied respectively.The research content of this article mainly includes the following aspects:(a)By introducing an electrostatic field into the conventional melt-blown apparatus,the average diameter of the melt-blown fibers was reduced from 1.69 to 0.96 m with the experimental setup,and the distribution of fiber diameters was narrower.(b)The morphology,web structure,pore size distribution,filtration efficiency,and the stress and strain behavior of the PP nonwoven fabric thus prepared were characterized.The results show that although the mechanical property of the electrostatic-assisted melt blown fabric was deteriorated,it has smaller average pore size and improved filtration efficiency,so that the fabric can be widely used in air filtration.(c)Highly-oriented poly(m-phenylene isophthalamide)/polyacrylonitrile multiwalled carbon nanotube(PMIA/PAN-MWCNT)composite nanofiber membranes with excellent mechanical strength and thermal stability are successfully produced using electrospinning.It is demonstrated that the cooperation of multi-walled carbon nanotubes(MWCNT)and high-speed rotating collection is beneficial to the acquisition of highly oriented fibers and effectively improves the mechanical strength of the membrane along the orientation direction.(d)The mechanical properties,high temperature resistance,flame-retardancy,and chemical stability of PMIA/PANMWCNT membranes were analyzed comprehensively.The results show that the tensile stress of membrane is enhanced significantly from 10.6 to 20.7 MPa,benefiting from the highly oriented alignment of the fibers as well as the reinforcing effect of MWCNTs on the fibers.Furthermore,the stressing process of single fiber and fiber aggregates is carefully simulated.The composite nanofiber membrane has the advantages of both PMIA and PAN,possessing high temperature resistance,flame-retardancy,and chemical stability,for an ideal high-temperature material.In short,the as-prepared PMIA/PAN-MWCNT composite membrane with excellent comprehensive property emerges a promising application in many fields.(e)Amphoteric cotton nonwovens with unidirectional water-transport through the thickness of the fabric were prepared using atmospheric plasma technology.A thin layer of polymerized Hexamethyldisiloxane(HMDSO)was locally deposited onto a cotton nonwoven fabric,so that only the treated surface(TS)was hydrophobic(water contact angle = 153°),while the untreated surface(UTS)remained hydrophilic(water contact angle = 0°).(f)The amphoteric cotton nonwovens can exhibit the unidirectional watertransport function due to its asymmetric wettability.Through experiments,the unidirectional water-transport performance was quantitatively characterized.In addition,the air and vapor permeability,pore size distribution were also characterized.The results show that the amphoteric cotton nonwovens have excellent unidirectional water-transport function while maintaining their air and vapor permeability.