Preparation And Formation Mechanism Of Nano Al <sub> 2 </ Sub> O <sub> 3 </ Sub> Particle / Pvdf Composite Hollow Fiber Membrane

In this paper the Al₂O₃ nanoparticle/PVDF hollow fiber composite membrane was prepared by immersion precipitation phase inversion technique. The influences of casting solution composition and preparation condition on the membrane morphological structure and characteristics were investigated, and the composite membrane formation mechanism was discussed.The effects of polymer concentration, nonsolvent, additive, dry journey and Al₂O₃ nanoparticle on membrane structure and property were mainly studied. It was discovered that the lower polymer concentration, appropriate nonsolvent content, small molecular weight PVP additive and litter longer dry journey were propitious to obtain the porosity and high flux separation membrane.After experiments such as viscosity, SEM, FT-IR, XRD, TG-DTA, mechanics capability, contact angle, bubble point, water flux and porosity tests, it was found that the addition of Al₂O₃ nanoparticle caused a strong increase of the viscosity, that made membrane formation easier, the skin layer and cross membrane thickness augmented, more porous macrovoid wall was formed in the composite membrane, the α phase PVDF decreased and β phase PVDF increased, the composite membrane was a physical blend membrane, thermal stability and crystal degree improved, mechanical strength raised and flexility descend, hydrophilic performance, surface porosity and water flux enhanced.The influences of Al₂O₃ nanoparticle on the formation mechanism of composite membrane sublayer macrovoid structure and membrane surface micropore were researched. The formation of composite membrane sublayer macrovoid included three processes, which were the birth of macrovoid, the formation of macrovoid toplayer figure and the growth of macrovoid. The first step consisted of nucleation, skin layer solidification, solid-liquid phase separation and macrovoid outgrowth. The addition of Al₂O₃ nanoparticle was helpful to minish macrovoid, enhance crystal degree, improve the hydrophilic performance, increase pore diameter and surface porosity of the composite membrane.