Microfiber Release And Related Influencing Factors During The Usage Of Typical Fabric Products

Microfibers have been considered as the main form of microplastics(MPs)in the environment for a long time.It is an important research topic in the field of environmental and ecological science.Textiles are considered as an important source of terrestrial microfibers.Current studies shew that both synthetic fibers and natural fibers can bring health risks to environmental organisms in the form of microfibers,However,it is not clear how textiles affect the shedding behavior of microfibers.Especially since the outbreak of COVID-19,the demand for protective masks and wet or dry disinfection wipes has increased dramatically,which lead to increasingly prominent ecological threat.Most masks and wipes are non-woven products made of directional or random fibers.However,there is little research on the microfiber produced by wiping nonwoven products.As a new pollution source of MPs,the potential role of non-woven products in the ecosystem has not been fully recognized and considered.Therefore in this study,16 non-woven products(5 disposable dry wipes,7 disposable wet wipes and 4 masks)and 13 common woven products(5 T-shirts,4fitting clothes,2 baby clothes and 2 jackets)are taken as the research objects and the release behavior of microfibers is simulated by daily washing and wiping.Stereoscopic sorting and Fourier transform infrared micro spectrometer were applied(μ-FTIR)to analyze the morphological characteristics and polymer compositions of microfibers.This study also examined the effects of external wiping conditions(wiping times,wiping force,moisture content),fiber mechanical properties(entanglement coefficient,fiber extraction force,bending degree)and washing factors(washing temperature,washing times,washing speed detergents and softeners),on the release behavior.Finally,the potential risks were assessed based on the total amount of shed microfibers,which provides a basis for the formulation of relevant standards and policies.The main conclusions are listed as follows:(1)Dry wipes(77-568 p)can release more microfibers than wet ones(21-190 p)in a single wiping process.All shed microfibers are white and translucent with a wide length range(50-10000μm).The lengths of microfibers from the wet wipes are significantly shorter than those from the dry wipes.The average numbers of microfibers shed from 4 masks ranges between 14 and 19,which were obviously less than those shed from wipes under the same wiping conditions.The microfibers shed from dry wipes were cellulose,PET and polypropylene(PP).Wet wipe can shed more microfibers in higher wiping forces and wiping times.Under high wiping forces of 9.8N(r=0.983,p<0.01)and 6.86 N(r=0.960,p<0.01),a significant positive correlation between the number of microfibers and wiping time was found.The number of microfibers shed in dry state increased by 3.96 times in average compared with the wet state,and the moisture content was negatively correlated with the number of shed microfibers(r=-0.992,p<0.01).The high degree of fiber entanglement can reduce the shedding ability of microfibers(r=-0.664,p<0.05).In addition,bending degree(β=-5.05,95%CI:-7.71,-2.40,p=0.002)and fiber extraction force(β=-5.05,95%CI:-7.71,-2.40,p=0.002)also present a negative correlation with the shedding coefficient.According to the calculation,3-5 kg wipes can release 2.60×10~5-4.33×10~5 microfibers during wiping.The wipes used each year in China can shed at least 2.09×10~3 kg microfibers.In addition,the inhalation risk of shed microfibers is estimated as a non-negligible potential risk source.(2)Woven fabric products can release microfibers in the washing process.The concentrations of microfibers in the washing wastewater of different products varies greatly(606 p/L-4918 p/L).The average abundance of microfibers in the washing wastewater discharged from a single washing of each woven product is 2481±152 p/L.The length of shed microfibers ranges from 471μm to 689μm.The compositions of shed microfibers were cellulose(cotton),polyester(PET),nylon(PA),polyurethane(PU)and acrylic(PAN),which is consistent with the identification on their labels.The woven fabric with cellulose(cotton)as the main raw material has a high shedding capacity.The ability of shedding microfibers gradually stabilized with the increase of washing times.The number of microfibers dropped significantly from the first washing to the fifth.The Pearson analysis found that there was a negative correlation(r=-0.889,p<0.05).The increase of washing speed(r=0.961,0.988,p<0.05)and washing temperature can significantly increase the microfiber release level of the same woven fabric products.An increase of 100 RPM in washing speed can release additional 261.8±47.3 microfibers in each liter of washing sewage from cotton clothes,and additional169.2±4.9 microfibers in each liter of washing sewage from PET clothes.Compared with the washing behavior at 30℃,the microfiber abundance in the washing sewage produced at 60℃increased by 42.2±3.2%on average.In addition,there was a significant positive correlation between microfiber release and detergent dosage(r=0.908,p<0.05),while the softener did not show a similar effect.According to the overall shedding situation,the total amount of microfibers released after a single washing at 30℃ranged from 26700 to 211500,while the total amount of microfibers released from a single washing at 60℃is between 32400 and 260300.If the clothes produced in China in a year are all washed for once,about 4211kg of microfibers can be released.