Study Of Preparation Of Fluorescent Polyethylene/Polypropylene Nonwoven Fabric By Radiation Modification And Its Application

The traditional fluorescent fibers are mainly prepared through physical processes such as melt spinning,solution spinning,electrostatic spinning,and surface coating.The luminogens and the polymer matrices in the as-prepared fluorescent fibers are only combined by physical interaction,which directly leads to the inherent defects,including weak fluorescence intensity,low fluorescence quantum yield,and poor fluorescence stability.Therefore,exploring a new fluorescent fiber preparation process that satisfies not only the luminogens covalently attached on the polymer matrices but also the industrial production is urgently required.Radiation-induced graft polymerization（RIGP）as an advanced modification technology not only covalently introduces functional groups on the polymer matrices,but also achieves large-scale modification for polymer matrices.At present,although many functional polymers have been prepared via RIGP,the preparation of fluorescent fibers has not yet been studied.Among the traditional synthetic fibers,polyethylene/polypropylene nonwoven fabric（PE/PP NWF）is a commercial product with simple preparation process,which has excellent flexibility,air permeability,thermal stability,mechanical property,and chemical stability.However,there are few studies on preparation of functional PE/PP NWF.Therefore,in this study,we have covalently introduced different luminogens on the PE/PP NWF to prepare a series of functional nonwoven fabrics with superior fluorescence properties via RIGP and investigate their application.Four main aspects are as follows:（1）The discovery of aggregate-induced emission（AIE）compounds has made up for the shortcomings of classical fluorescent aromatic compounds,which greatly expands the application of luminogens in their concentrated solutions or solid materials.In this chapter,the AIE-based tetraphenylethylene（TPE）units were introduced on the PE/PP NWF via combining electron beam pre-radiation-induced graft polymerization technology and subsequent chemical modification,obtaining an AIE-based fluorescent nonwoven fabric（PE/PP NWF-TPE）.The optimal conditions for grafting the poly（glycidyl acrylate）（PGMA）chains was 100 k Gy of absorbed dose,65℃of reaction temperature,and 1 h of reaction time.PE/PP NWF-TPE emitted a green light under 365 nm UV light.The luminescent centers are TPE units.The fluorescence intensity enhances with the increase of TPE unit density,indicating the AIE effect.The fluorescence quantum yield is about 13.26%and the fluorescence lifetime is about 9.2μs.Besides,PE/PP NWF-TPE displays excellent fluorescence stability after 20accelerated launderings,immersing 12 M HCl or Na OH solutions for 3 days.（2）Compared with aromatic luminogens,nonconjugated luminogens have the advantages of low toxicity and good biocompatibility.In order to prepare environmentally friendly fluorescent nonwoven fabrics,in this chapter,the nonconjugated pentaethylene hexaamine（PEHA）units were introduced on the PE/PP NWF,obtaining a nonconjugated fluorescent nonwoven fabric（PE/PP NWF-PEHA）.PE/PP NWF-PEHA emits a blue light under 365 nm UV light and displays superior fluorescent properties of strong fluorescence intensity,high fluorescence quantum yield（～83.35%）,and excellent fluorescence stability.PE/PP NWF-PEHA also has good dyeing performance and the fluorescence still maintained.PE/PP NWF-PEHA can also be tailored into diverse shapes and printed in situ with high resolution.The versatility of the method is also demonstrated by fabricating fluorescent materials with different polymer matrices such as Nylon 66 fiber and PET membrane。（3）Classical fluorescent aromatic compounds have the aggregate-caused quenching（ACQ）effect,which limit the application in their concentrated solution or solid materials.In this chapter,we reasonably use the ACQ effect to prepare fluorescent nonwoven fabrics with tunable fluorescent properties.The ACQ-based pyrene（Py）units were introduced on the PE/PP NWF,obtaining a series of Py-based fluorescent nonwoven fabrics（PE/PP NWF-Py）.The Py density increases with increase of the amination time,which has important effects on the morphology and thermal stability of PE/PP NWF-Py.The Py units are the fluorescence centers.The fluorescence color of PE/PP NWF-Py changes from blue to green,and the fluorescence intensity,quantum yield,and lifetime can be regulated by controlling the amination time.In addition,PE/PP NWF-Py exhibits excellent fluorescence stability after 20 accelerated launderings,immersing common organic solvents,12 M HCl or Na OH solutions for 3 days.Furthermore,PE/PP NWF-Py can clearly distinguish different MAHs via a simple fluorescence response test.（4）Ammonia as a toxic gas poses a serious threat to the ecological environment and humans.It is still a challenge to detect ammonia with efficiency and visualization.In this chapter,the ACQ-based pyrene（Py）units and the-SO₃H groups were introduced on the PE/PP NWF,obtaining a Py/SO₃H-based fluorescent nonwoven fabric（PE/PP NWF-Py/SO₃H）.PE/PP NWF-Py/SO₃H has dual fluorescence emission in the blue and red range,respectively,resulting in emitting a purple light under 365 nm UV light.PE/PP NWF-Py/SO₃H also has high fluorescence quantum yield（32.65%）and long fluorescence lifetime（45.2μs）.Besides,there is a synergistic effect between pyrene units and the-SO₃H groups,promoting PE/PP NWF-Py/SO₃H has rapid and exceptional response toward ammonia gas and the detection limit is about 0.6 ppm.