| Recently,with the improvement of people's living standards and the advancement of science and technology,clothing has not only been limited to the traditional role of warming the body,some functional textile fabrics have been rapidly developed because they can better meet people's needs.Waterproof and breathable fabric is one of the typical representatives.They can prevent rain and snow from invading under certain pressure.At the same time conducting the moisture generated by human body movement and maintaining the thermal and moisture comfort,which have broad applications in protective clothing,medical field,building exterior wall and water treatment industry.It is reported that the global waterproof and breathable textiles market size is expected to reach USD2.44 billion by 2025 registering a CAGR of 5.5%,indicating a huge market demand.At present,there are three types of waterproof and breathable fabrics:high density fabric,coated fabric,and laminated fabric.The high-density fabrics are good in moisture permeability but insufficient in water repellency due to their large pores.While the coated fabrics possess high hydrostatic pressure,but the moisture permeability is poor and the wearing is uncomfortable.Therefore,laminated fabrics have become the mainstream of waterproof and breathable fabrics in the current market because of its outstanding comprehensive performance.The core layer of the waterproof and breathable laminate fabric is a functional membrane with excellent waterproofness and breathability,which can be prepared by various processing techniques such as casting technology,biaxial stretching,phase separation,flash evaporation or the like.However,these preparation techniques often have some limitations such as complicated equipment processes,limited material sources and high costs.Electrospinning is a new technology for preparing continuous nanofibers using a polymer solution or a melt under high electric field to form a continuous nanofiber at a high speed.Because of its broad availability to kinds of different polymers,remarkably low cost and straightforward process,electrospinning has been identified as the most effective method.Besides,the electrospun membrane has a small pore size and a high porosity,which coincide well with the basic criteria of designing W&B materials.The current high-performance waterproof and breathable membranes are fluorinated microporous membranes,although fluorine-containing compounds?especially long perfluorinated segments?can impart fibrous membranes with remarkable hydrophobicity,people found that perfluoroalkyl acids produced by the degradation of perfluoro or polyfluoride are hardly to degrade,easily accumulated in organisms,and exhibiting long biological half-lives,which do harm to both human beings and the environment.In addition,although some researcher attempted to use a fluorine-free water repellent,it is often in the form of various coating treatment,which has drawbacks of complexity of the preparation process and poor durability.Therefore,in the present work,We rationally fabricated an eco-friendly fluorine-free breathable and waterproof functional membrane with interbonding structured fibers via emulsion electrospinning and thermal treatment,combining hydrophobic agent PMHS and a thermoplastic polyurethane PU.It not only satisfies the concept of environmentally friendly and sustainable development,but also meets the demand of good durability.This work focuses on the effects of DMAc/IPA ratio,concentration of hydrophobic agent PMHS and heat treatment temperature on the surface morphology,pore size and pore size distribution,surface wettability,mechanical properties,permeability as well as the waterproofness and breathability of the prepared membrane.Firstly,a series of nanofiber membranes with different PMHS concentrations were prepared at a PU concentration of 14 wt%and a ratio of DMAc/IPA of2/1.When the concentration of PMHS was optimized as 7.5 wt%,considering that the corresponding water pressure resistance of 34.6 kPa cannot meet the requirements of the national standard GB/T32614-2016 for the waterproofing of the Class I jacket?50 kPa?,they were chosen for further processing.The latter half of the experiment focused on the regulation of the heat treatment temperature.When the temperature was too low,the fiber membrane didn't substantially change,and when it was too high,a large amount of adhesion structure appeared.Heating at 100°C for 1.5h is an equilibrium point.Under this heat treatment process,the declined apertures not only brought about greatly improved waterproof capability but also doubled the mechanical strength.Consequently,the prepared membranes exhibited a sufficient waterproof property of 54.1 kPa,which was far more than that of pristine electrospun PU membranes.Besides,it reached excellent tensile strength 14.1MP and elongation 265.5%,robust moisture permeability 9.5kg m-2d-1.This study aims to provide a simple and effective method for the green design of waterproof breathable fabrics. |
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