Crosslinked PVA/PAA films were prepared with 10 wt% PVA/PAA solution. The 10 wt% PVA/PAA solutions were stirred at 85 C for 2 h for dissolution and PEG 400 (2 g; 20 wt% of PVA) was added to the 10 wt% PVA/PAA solution. The mixed solution was stirred for 2 h at a constant temperature of 85 C.The weight percentage of glyoxal to PVA ranged from 0 to 10
The requisite amount of phosphoric acid was added to maintain the pH value within the range of 2–3. This PVA/PAA/glyoxal solution was stirred vigorously over the course of 2 h at 85 C. The solution was cast on a glass plate (400 mm × 400 mm) to form a 40 m thick film using an applicator. The cast film was dried at 60 C for 24 h.