Study on porous silk fibroin materials: 3. Influence of repeated freeze-thawing on the structure and properties of porous silk fibroin materials

The influence of repeated freeze-thawing on pore structural characteristics and physical properties of porous silk fibroin materials prepared by freeze drying were studied. It showed that when quick-frozen silk fibroin solution was repeatedly thawed and frozen before being vacuum dried, thus pore size of prepared porous silk fibroin materials increased from 67 mum to about 120 mum, and pore density decreased from 80 per square millimeter to about 28 per square millimeter, at the same time compression ratio and moisture permeability increased from 22.7% and 230 g/m(2) hr to about 33.7% and 308 g/m(2) hr, respectively, tensile strength and dissolvability in hot water decreased from 20.2 N/cm(2) and 42.7% to about 12.5 N/cm(2) and 26.1%, respectively. Both the times of repeated thawing and the thawing temperature had a certain influence on the above mentioned pore characteristic parameters and physical properties. Copyright (C) 2001 John Wiley Sons, Ltd.