POLY(HYDROXYBUTYRATE) AND POLY(HYDROXYBUT YRATE-CO-HYDROXYVALERATE) MICROFILTRATION MEMBRANES - FORMATION - DEPENDENCY ON HYDROXYVALERATE CONTENTS

Filtration properties and structure of polyhydroxybutyrate, poly(hydro xybutyrate-co-9% hydroxyvalerate) and poly(hydroxybutyrate-co-22% hydr oxyvalerate) microfiltration membranes prepared by the inversion phase method are correlated with coagulation bath composition, non solvents percentages (% NS) (tetrahydrofuran, dimethylformamide, ethanol) and hydroxyvalerate contents (% HV). Ternary phase diagrams are discussed with respect to polymers solubility parameters and solvent-non solvent mixtures solubility parameters just as phase separation occurs. The s low or rapid membranes formation was studied by comparing the initial solution composition to the binodal curve values. Volumic fluxes, sele ctivity and % NS variations were explained from this concept. Only the 9% HV copolymer presents a spherolitic structure which results from a larger cristallization velocity during this phase inversion method co nditions.