Preparation of poly(L-lactic acid) microfiltration membranes by a nonsolvent-induced phase separation method with the aid of surfactants

Microfiltration membranes of poly(L-lactic acid) (PLLA) have been prepared by a nonsolvent-induced phase separation method with the aid of surfactants. Surfactants with hydrophilic-lipophilic balance (HLB) values of 14.9-15.6 were found to be useful in reducing the shrinkage in thickness of the PLLA membrane. Among the surfactants examined, Tween 80 was the best for preparing microfiltration membranes. The surfactant allowed instantaneous phase separation and seemed to enhance the diffusion of water in the PLLA solution during structure formation. The membrane had asymmetric finger-like structures and showed low membrane resistance and high bacterial cell retention when the membrane was prepared from a 10 wt% PLLA solution in 1,4-dioxane containing 10 wt% Tween 80. Bovine serum albumin molecules passed through the membrane suggesting that the membrane functions as a microfiltration membrane. The membrane was stable at 25 °C but degradable at 60 °C in wet conditions. The membrane can be applied as a compostable microfiltration membrane in food and biochemical industries.