Preparation of specimen:
Ten rectangular specimens each with a length of 150mm, and a width of 50mm shall be cut from each sample plywood. The longitudinal direction of specimen shall be parallel to the fiber direction of the face veneer.
Method of test:
1. Specimen conditioning: The specimens from the same sample plywood shall be wrapped tightly and separately with plastic (PE) bag. The specimen conditioning shall be performed in a thermal chamber with a temperature adjusted to (20±1)℃ for at least 1 day.
2. Preparation of chemical solution: Lodine solution (0.05 mol/L), Sodium thiosulfate solution (0.1 mol/L), Sodium hydroxide solution (1 mol/L), Sulfuric acid solution (1mol/L), Starch solution, Formaldehyde standard stock solution and Acetylacetone-ammonium acetate solution.
3. Acquisition of formaldehyde: A 120-mm-diameter, 60-mm-high crystallizing dish containing 300 mL of distilled water was placed in the bottom of a 240-mm-diameter desiccator with a capacity of (10±1)L as shown in specimens were clamped in a metal support, with no contact among the specimens and allowed to stand in the crystallizing dish at(20±1)℃ for 24h. Formaldehyde released from the specimens was absorbed by distilled water, which was subsequently used as the sample solution.
4. Quantification of formaldehyde concentration: The formaldehyde concentration of the sample solution can be determined by acetylacetone spectrophotometry .The method is making colorimetric quantification with a photoelectric spectrophotometer or a photo-electrometric colorimeter that can measure the wavelength to about 415 nm.
5. Preparation of calibration curve: Place 0, 5, 10, 20, 50, and 100 mL of each of the formaldehyde standard solutions into individual 100mL volumetric flasks, respectively. Add distilled water to the mark. The solutions are used to plot the calibration curve. Take 25 mL from each solution and proceed with operations in Sect Acetylacetone spectrophotometry. Plot curves showing relationships between content of formaldehyde (0~3 mg/L) and absorbance. The slope (f) can be calculated from this curve.
6. Calculation of concentration of formaldehyde: The concentration of formaldehyde can be calculated as follows.
  G = f x (Ad-Ab)
  in which, G：concentration of formaldehyde in sample solution (mg/L)
  　 f ：slope of calibration curve (mg/L)
  　　　 Ad：absorbance of sample solution
  　　　Ab：absorbance of blank solution ( distilled water)

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Taiwan Forestry Research InstituteTaiwan Forestry Research Institute

Test for Formaldehyde Emission from Wood-based Pan