Preparation and properties of alkali lignin-poly ( vinylalcohol ) ( PVA ) reaction membrane with formaldehyde crosslinker#br#

The wheat straw alkaline lignin-poly (vinylalcohol) (PVA) chemical reaction membranes were prepared on the basis of wheat straw alkaline lignin by crosslinking reaction of formaldehyde and PVA by the film casting method. The effects of formaldehyde content on mechanical properties of membranes were investigated. And the mechanical properties, thermal properties, absorbability of ultraviolet light, gas permeability and solvent resistance were measured. The results showed that the tensile strength and elongation at break of membranes were 21.81 MPa and 682% when the mass ratio of formaldehyde was 3.0%. The surface and fracture surface of membranes were well-distributed and smooth. The most violent decomposition temperature of the membranes was 300 ℃and the residue of membranes was 7.8% at 465 ℃, both of which were higher than PVA membrane, indicating a better thermal stability of membranes. Also the membranes exhibited anti-UV according to the strong absorption capacity of light between 200 -500 nm. The nitrogen permeability of membranes was 1.580 x10 -8 m3 / (m2daykPa), which was much lower than PVA membrane 2.696 x10 -7 m3 / (m2daykPa). Besides, the membranes were soluble in water and acetic acid, and insoluble in isopropanol, carbon tetrachloride and petroleum ether.