Regular copolyamides, 7. Water absorption in regular copolyoxamides

Water absorption at 93% relative humidity and 25°C was determined for 12 regular aliphatic/aromatic copolyoxamides. The equilibrium water absorption ranges from 7% to 30%, varied with the polymer structure and is highest in polymers with high amide concentration. The water absorption is reversible and seems to consist of a two‐step process, rapid absorption of water by polymer followed by a slower second stage as equilibrium is approached. These polymers have low crystallinity and the water absorption does not occur in crystalline regions. All water is bound to the polymer; it may be freed by heating the hydrated polymer above 100°C, but rebinds completely at room temperature.