2.2. Preparation of NR sheets
Each NR sheet was prepared in a pan by adding coagulant into diluted NR latex (2,000 mL filtered fresh NR latex + 3000 mL water). For formic and acetic acids, 300 mL 2% (v/v) were used. In the case of wood vinegars, 300 mL 50% (v/v) was chosen for preparing the NR sheets. The mixture of diluted latex and coagulant was left for 2 h for complete coagulation. The obtained slabs were compressed between two steel rolls and then washed with water before drying at room temperature with relative humidity of 50–60% for a week. The product obtained from this process is called pre-drying NR sheet and its further processed by drying at 50–60 °C for 2 days to be the dry NR sheets. The NR sheets coagulated by using formic acid and wood vinegar mixtures (3 mL formic acid + 75 mL wood vinegar + 222 mL water for each pan) were also prepared for antifungal efficiency comparison. The pH of all coagulant aqueous solutions was in the range of 2.6–3.1.