Development of eco-efficient micro-porous membranes via electrospinning and annealing of poly (lactic acid)

Environment-friendly membranes were fabricated from poly (lactic acid) (PLA) via electrospinning technique. In order to control the pore size of the electrospun membranes and to improve their mechanical properties, a series of annealing treatments were carried out on the electrospun membrane. The effect of annealing treatment on membrane structure, porosity, hydrophobicity and mechanical properties was investigated. The annealing time and temperature were varied from 30 to 120 min and from 90 to 105 °C, respectively. When either annealing time or temperature was increased, membrane shrinkage, fiber thickening and fusion were observed, which resulted in pore size reduction from 2.8 to 0.9 μm, along with a reduced porosity. On the other hand, annealing resulted in an increase in the membraneʹs mechanical strength, as measured by the Mullen burst test. Moreover, Youngʹs modulus of the annealed membranes increased dramatically by about 2500%. The contact angle of the membrane was also affected by the annealing process. Based on the properties of the electrospun PLA membranes, they were proposed as microfiltration membranes. Vacuum-filtration tests of a solution containing TiO2 particles were conducted. The filtration tests showed that the annealing treatment, which varied the membrane properties, had a significant impact on membrane performance, in terms of both flux and particle rejection.