Preparation And Properties Of Unidirectional Water Permeable Membrane

Polyvinylidene fluoride(PVDF)has excellent chemical stability and mechanical properties,and good film-forming properties.The electrospinning technology combined with PVDF can be prepared nanofiber film.The fiber membrane prepared from polyurethane(PU)material can provide good breathability and moisture permeability,and has great potential for application in the production of waterproof and moisture-permeable film material.In this paper,the water repellent properties of PU and PVDF are used and combined with hydrophilic materials to prepare a monotropic wet film material.In this paper,using PU and PVDF as raw materials,electrospinning fibers are deposited on the surface of hydrophilic materials using electrospinning technology to obtain a film material with a moisture gradient in the vertical direction.The morphology of spun fibers was observed by scanning electron microscopy.The optimal spinning parameters of PU were as follows: the volume ratio of THF to N,N–dimethyl-formamide(DMF)was 3:1,spinning solution concentration of 14%,spinning voltage of 25 kV,the solution flow rate 2ml/h,spinning receiving distance of 15 cm,wheel speed 500rmp;The optimal spinning parameters of PVDF are as follows: the volume ratio of solvent DMF to acetone is 3:2,the spinning solution concentration is 15%,the spinning voltage is 20 kV,the spinning speed is 1.0ml/h,Receiving distance 15 cm,wheel speed 500 rpm.In order to investigate the effect of different thickness of hydrophobic layer on unidirectional water-permeable performance,unidirectional water-permeable materials with different hydrophobic layer thicknesses were prepared by controlling different spinning times in the experiment.The liquid permeation time was tested respectively.The results showed that when the PU spinning time was 15min-40 min,one-way water permeation in the vertical direction could be achieved.And as the spinning time increases,the time of liquid drop penetration also increases.When the PVDF spinning time is 10min-30 min,one-way water permeation in the vertical direction can be achieved,and as the spinning time increases,the droplet penetration time also increases.Different hydrophilic layer materials were used to investigate their effect on unidirectional water permeability.The result shows that when polyester and pure cotton are used as hydrophilic layer,the droplet transmission time is short,the unidirectional wetting effect of pure cotton is better,and the unidirectional wetting effect of polyester is second;Polypropylene non-woven fabric as a hydrophilic layer,the droplets of the longer transmission time,the worst one-way moisture guide.