Preparation Of A Composite Reinforced Three-hole Hollow Fiber Membrane

Hollow fiber membranes were widely used in microfiltration,ultrafiltration and membrane distillation due to its advantages.But in the large-scale application of hollow fiber membranes,membrane strength and membrane fouling were major problems affecting the stable operation of membrane system.Membrane broken often happened due to the impact of airflow and water flow,and the flux declined due to the inevitable concentration polarization and membrane fouling,result in the shorter life of membrane module.So the development of high strength and anti-pollution of hollow fiber membrane have great values.For those purposes,this paper studied the relationship between the melt-spinning process and the fiber structure and properties,and high strength PVDF fibers were obtained.Secondly,the tri-bore PVDF hollow fiber membranes of high strength were prepared by composite technology.Then wavy tri-bore PVDF membranes with regular waves and different diameters were prepared in order to improve the anti-pollution performance.In order to obtain poly(vinylidene fluoride)(PVDF)fibers with high tensile strength,orthogonal test and single factor tests were designed to explore the best process parameters of melt spinning of PVDF fibers.Thermal Analysis(DSC),infrared spectrum(FTIR),X-ray diffraction(XRD),and tensile test were carried out to analyze the crystalline structure,crystal orientation and mechanical properties of the fibers.The results showed that:the important order of relevant factors on tensile strength was:winding speed>spineret temperature>spineret size>air gap,and the tensile strength were increased with the increase of draw ratio.Tri-bore PVDF hollow fiber membranes were prepared through special spinneret by non-solvent induced phase separation(NIPS).The effects of the air gap distance,wall thickness,and spinneret structure on the morphology and basic performance including ultrafiltration water flux,the maximum aperture,fracture pressure,permeability coefficient,membrane distillation flux,breaking strength and elongation of tri-bore PVDF membranes were investigated,and the optimized membranes with both good separation and mechanical properties were obtained.