Preparation Of Janus Fabric And Study On Directional Water Transport Performance

The Janus material is a functional material with asymmetric properties(i.e.physical asymmetry and chemical asymmetry)in the same structural system,which can actualize directional liquid transportation.This characteristic makes it a vital application in the fields of protective clothing,oil-water separation,air filtration,biomedicine and fluid manipulation.However,the existing Janus materials have defects such as complicated preparation process,fluorine content of materials,and poor tolerance and controllability,which restricts its practical application in daily life.Hence,the development of Janus materials with simple preparation,good tolerance and strong controllability has become the focus of researchers.To investigate the mechanism of asymmetric structure on directional water transport,three different types of Janus fabrics were prepared: the first type is the Janus fabric(PS-x/PET)with different thickness hydrophobic membranes constructed based on the same modified PET fabric;The second type is to construct the same thickness hydrophobic layer based on different modified PET fabrics(PS/PET-y);The third type is to construct hydrophilic membranes of different thicknesses based on the same thicknes PET and hydrophobic layers(PS/PET/PVA-z).The effects of physical asymmetry and chemical asymmetry on the unidirectional water transport properties of PS/PET double-layer and PS/PET/PVA three-layer Janus fabrics were studied.The micro-morphology of the surface and cross-section of Janus fabric was observed by scanning electron microscopy(SEM).The wettability and mechanical properties of the fabric surface were tested by contact angle tester and universal strength machine.The pore structure of Janus fabric was analyzed by pore and aperture analyzer.The viscosity of water droplets in hydrophobic layer of Janus fabric was tested by "push","pull" and angle reversal,and its directional transport behavior was also tested by liquid permeation test at the interface of both sides of the fabric.The results show that the hydrophobic layer thickness can directly affect the water transport type in Janus fabric.With the increase of the thickness of the hydrophobic layer,the change trend of water transport type was: two-way transportation?directional transportation?two-way non-transport,Therefore,the hydrophobic layer only has a directional water transport performance within a certain thickness range.The wetting deviation between the two layers of Janus fabric can adjust the directional transport capacity of water in the fabric.The greater the deviation of wettabilitybetween hydrophilic layer and hydrophobic layer,the better the directional water transport performance.In PS/PET/PVA three-layer Janus fabrics,the pore structure and capillary force increase with the increase of hydrophilic layer thickness,while the directional water transport performance of the fabrics was determined by the interaction between the resistance produced by pore structure and capillary force(attraction).In summary,the hydrophobic layer thickness can play a "coarse adjustment" effect in the obtaining directional water transport function for fabric,while the wettability deviation and the hydrophilic layer thickness can be "finely tuned" to the optimal directional water transport level.