| As the aging population in China accelerates and the policy of encouraging childbirth gradually relaxes,the market demand for disposable diapers has rapidly increased.Nonwoven materials,with advantages such as safety,hygiene,and ease of processing,have become the preferred material for producing disposable diapers.Surveys show that baby diapers still have some usage problems,including poor urine absorption,leakage,reverse osmosis,and the tendency to cause skin redness after use.As the layer directly in contact with the skin,the wicking and anti-reverse osmosis properties of the diaper surface layer are directly related to the above problems.Therefore,this study aims to develop a unidirectional water-guiding and anti-reverse osmosis nonwoven surface layer material and focuses on researching the unidirectional water-guiding and anti-reverse osmosis properties of the diaper surface layer to prepare a composite surface layer with unidirectional water-guiding and anti-reverse osmosis functions.The main research content and testing analysis conclusions of the project are as follows:(1)A single-layer electrospun micro-nano-fiber film composite ES hot-air surface layer prepared from thermoplastic polyurethane elastomer(TPU)/polyvinylpyrrolidone(PVP)was designed,and the effects of the mass fraction of the solution suitable for electrostatic spinning,different blending ratios of the materials in electrostatic spinning on the performance of the composite surface layer,and the effect of the thickness of the electrospun micro-nano-fiber film on the performance of the composite surface layer were investigated.First,through concentration gradient electrospinning experiments,it was determined that the optimal total mass fraction of TPU:PVP=1:1 electrospinning solution was 16wt%under the conditions of electrospinning voltage of 35-45kw and receiving distance of 10cm.Secondly,by controlling the total solution mass fraction to 16wt%,TPU/PVP electrospun nanofiber membranes were prepared with different TPU/PVP ratios.It was determined that when the total solution mass fraction was 16wt%and TPU:PVP=8:8,the composite surface layer material had excellent one-way water permeability with a cumulative one-way transport index of 624.63%.The composite layer had good adhesion,and after 20 friction cycles,the area loss rate of the TPU/PVP electrospun nanofiber membrane was 1.44%.At the same time,the composite layer had a fast liquid(physiological saline simulating urine)penetration speed and had a certain reverse osmosis effect,with a penetration speed of 3.14s(ES hot-air layer was 3.29s)and a reverse humidity of 3.4g(ES hot-air layer was 6.5g).Finally,the influence of different thicknesses of TPU/PVP electrospun nanofiber membranes on the performance of the composite layer was analyzed.The thinner the TPU/PVP electrospun nanofiber membrane,the larger the pore size and the better the air permeability.The liquid was easier to penetrate.The thicker the TPU/PVP electrospun nanofiber membrane,the better the mechanical properties and the improved friction resistance.Therefore,the adhesion of the TPU/PVP electrospun nanofiber membrane with the ES hot-air non-woven material was better.The test analysis shows that the composite layer has better performance when the thickness of TPU/PVP electrospun nanofiber film is between 1.8-2.5g/m2.After 20 times of friction experiment,the area loss rate of TPU/PVP electrospun nanofiber film is no more than 3.38%.The composite layer within this thickness range has a faster liquid penetration speed,with a liquid penetration speed of no more than 3.14s(compared to 3.29s for ES hot-air layer),and has a certain anti-reverse osmosis effect,with an anti-humidity of no more than 3.5g(compared to 6.5g for ES hot-air layer).(2)To enhance the unidirectional water-guiding and anti-seepage abilities of the composite layer,a double-layer electrospun micro/nano-fiber membrane composite ES hot-air material was designed using PAN/PVP and TPU/PVP,and the effect of different thickness ratios of each layer of the double-layer electrospun micro-nano layer on the performance of the composite surface layer was also investigated in order to obtain the best ratio,so that the performance of the composite surface layer can be optimized.Firstly,the optimal spinning concentration of PAN was determined to be 12 wt%at a spinning voltage of 35-45 kw and a receiving distance of 15 cm by the spinning solution concentration gradient spinning experiment.Secondly,by modifying PAN with PVP,a dense and well-connected micro/nano-fiber membrane was obtained.Finally,based on the wetting gradient theory,a three-layer composite structure was designed,with the upper layer being the ES hot-air material,the middle layer being the TPU/PVP electrospun micro/nano-fiber membrane,and the lower layer being the PAN/PVP electrospun micro/nano-fiber membrane.By adjusting the thickness ratio of the TPU/PVP layer and the PAN/PVP layer,the optimal composite layer performance was obtained.The experimental results showed that when the thickness ratio of the TPU/PVP layer to the PAN/PVP layer was 3:1,the performance was optimal.The double-layer electrospun micro/nano-fiber membrane was firmly combined with the ES hot-air material,with an area loss rate of only 12.7%after 20 times of friction,a cumulative unidirectional transmission index of 751.50%,a liquid penetration time of 3.0s,and a reverse moisture content of 5.5 grams.(3)In order to verify the water-permeability and anti-reverse osmosis performance of the composite surface layer on the diapers,the diapers were assembled using a single layer of TPU/PVP electrospun micro-nano-fiber membrane composite ES hot-air surface layer and PAN/PVP-TPU/PVP double layer electrospun micro-nano-fiber membrane composite ES hot-air surface layer,and compared with the comparison specimens and commercial original specimens for comparative analysis.Firstly,the diapers were assembled using different TPU/PVP blend ratios of electrospun micro-nano-fiber film composite ES hot-air surface layer and the performance was investigated,The results showed that under a certain thickness,the composite layer-assembled diaper had an effect on the urine infiltration rate and better urine diffusion performance,with excellent dryness.Among the four types of composite layer-assembled diapers tested,the performance of the diaper assembled with the 2#、3#composite layer(TPU/PVP=10:6、8:8,mass fraction of 16%)was the best.Secondly,diapers were assembled with composite surface layers of different thicknesses to explore their performance.The results showed that when the TPU/PVP electrospun micro-nano fiber membrane thickness was between 1.8-2.5g/m2,the composite layer had better performance,with a faster urine infiltration rate,longer diffusion length,better anti-reverse osmosis ability,and low reverse osmosis of only 0.05g.The diaper assembled with the composite layer of TPU/PVP electrospun micro-nano fiber membrane and PAN/PVP electrospun micro-nano fiber membrane with a thickness ratio of 3:1 was also tested for its performance.The experimental results showed that the diaper assembled with this composite layer had better urine infiltration rate,diffusion length,and anti-reverse osmosis ability than the ES hot-air layer-assembled diaper.Finally,The research results of this project show that the composite surface layer formed by the hydrophilic electrospun micro-nano fiber membrane and the hydrophobic ES hot-air layer has excellent one-way water permeability.The diaper assembled by the experimentally prepared composite surface layer has better diffusion of urine as well as anti-urine re-infiltration,which can improve the absorption rate of simulated urine during the actual use of the diaper,while keeping the surface layer dry and cool.The results of this research provide solution ideas and technical solutions for the development of new hygienic materials. |
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