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1、 1 AS/NZS 4266.16:2004 (Incorporating Amendment No. 1) COPYRIGHT Australian/New Zealand Standard TM Reconstituted wood-based panels Methods of test Method 16: Formaldehyde emissionDesiccator method PREFACE This Standard was prepared by the Joint Standards Australia/Standards New Zealand Committee TM
2、-005, Reconstituted Timber Panel Products, to supersedes AS/NZS 4266.16(Int):2001. This Standard incorporates Amendment No. 1 (February 2006). The changes required by the Amendment are indicated in the text by a marginal bar and amendment number against the clause, note, table, figure or part thereo
3、f affected. This Standard is equivalent to the industrial Standard harmonized between the wood panel industries in Australia, Japan and New Zealand, known as JANS 16. METHOD 1 SCOPE This Standard specifies a method for determining the quantity of formaldehyde emitted from particleboards and fibreboa
4、rds. 2 REFERENCED DOCUMENTS The following documents are referred to in this Standard: AS/NZS 4266 Reconstituted wood-based panelsMethods of test 4266.1 Method 1: Sampling, cutting, and conditioning of test pieces 4491 TimberGlossary of terms in timber related Standards 3 DEFINITIONS For the purpose
5、of this Standard, the definitions in AS/NZS 4491 and AS/NZS 4266.1 apply. 4 PRINCIPLE Emission of formaldehyde is determined by placing test pieces of known surface area in a desiccator, at a controlled temperature, and measuring the quantity of emitted formaldehyde absorbed in a specified volume of
6、 water during 24 h. AS/NZS 4266.16 Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 03 Mar 2008 AS/NZS 4266.16:2004 2 COPYRIGHT 5 APPARATUS 5.1 Desiccator Glass desiccator, with an enclosed volume of 12 2 L and fitted with a stainless steel wire grid or supporting platform of 230 10 mm in diameter and o
7、f the type specified in Clause 5.3. 5.2 Glass crystallizing dish Circular glass crystallizing dish, 115 1 mm inside diameter and 60 2 mm deep, and nominal size of 120 65 mm (based on external dimensions). 5.3 Wire grid Wire grid or support, 230 10 mm in diameter, made of stainless steel wire such th
8、at the distance between parallel pieces of wire is not less than 15 mm (see Figure 1). ? ? ? ? DIMENSIONS IN MILLIMETRES FIGURE 1 STAINLESS STEEL WIRE GRID FOR SUPPORTING THE TEST PIECES IN THE DESICCATOR Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 03 Mar 2008 3 AS/NZS 4266.16:2004 COPYRIGHT ? ? ?
9、FIGURE 2 EXAMPLE OF WIRE SAMPLE HOLDER TO HOLD THE TEST PIECES IN THE DESICCATOR 5.4 Sample holder Sample holder, made of stainless steel wire, to hold the test pieces upright in the desiccator (see Figure 2). 5.5 Temperature-measuring device A thermocouple or other temperature measuring device, cap
10、able of measuring temperature with an error limit of 0.1C, placed inside a desiccator of the type specified in Clause 5.1, which is located adjacent to the desiccator(s) containing the test pieces. 5.6 Spectrophotometer Spectrophotometer, capable of measuring absorbance in the range 410 to 415 nm. 5
11、.7 Water bath Water bath, capable of maintaining a temperature of 65 2C. 5.8 Volumetric flasks100 mL Six volumetric flasks, 100 mL, calibrated at 20C. 5.9 Volumetric flasks1000 mL Two volumetric flasks, 1000 mL, calibrated at 20C. 5.10 Bulb pipettes Bulb pipettes, 5, 10, 15, 20, 25, 50 and 100 mL, c
12、alibrated at 20C, or suitable auto pipette. 5.11 Micro-burette Micro-burette or auto dispenser. 5.12 Flasks Flasks, 100 mL, with stoppers. 5.13 Balance Balance, scale interval 0.001 g. Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 03 Mar 2008 AS/NZS 4266.16:2004 4 COPYRIGHT 6 REAGENTS 6.1 General Rea
13、gents and water of recognized analytical purity shall be used for the analysis. 6.2 Acetylacetone-ammonium acetate solution 150 g ammonium acetate are dissolved in 800 mL distilled or de-ionized water. 3 mL glacial acetic acid and 2 mL acetyl-acetone (2, 4-pentanedione) are added and thoroughly mixe
14、d into the solution. Distilled or de-ionized water is added to make 1 L and the solution is stored so that it is protected from light. The solution shall be discarded after three days and a fresh solution made. 7 TEST PIECE 7.1 Sampling Sampling and cutting of the test pieces shall be carried out in
15、 accordance with AS/NZS 4266.1. 7.2 Dimensions The test pieces shall be 150 1.0 mm in length and 50 1.0 mm in width. 7.3 Number of test pieces The number of test pieces shall be that which gives a total surface area, defined as the sum of the areas of the ends, sides and faces, as close as possible
16、to 1800 cm2. 7.4 Number of emission tests The emissions tests shall be carried out in duplicate. NOTE: For internal routine control, a single emission test may be sufficient. The difference between emissions of the two tests shall be within 20% of their average; otherwise a third emission test shall
17、 be carried out. 7.5 Conditioning The test pieces shall be conditioned in accordance with AS/NZS 4266.1 or for 7 days. The test pieces to be conditioned shall be separated by at least 25 mm and positioned so that free circulation of air occurs over all surfaces. NOTE: Test pieces containing low leve
18、ls of formaldehyde will absorb formaldehyde from the atmosphere when background levels of formaldehyde are high. Care should be taken to avoid such conditions during storage and conditioning by the use of a formaldehyde removal system or by maintaining low volumes of test pieces in the room. The bac
19、kground level is measured when a glass-crystallizing dish (Clause 5.3) containing 300 mL of distilled water is exposed to the conditioning atmosphere for 24 h, and the resulting solution is analysed. The maximum background level should be less than the nominal emission level of the test pieces (e.g.
20、, for test pieces from a sample with intended emissions of 0.3 mg/L, the background levels should be less than 0.3 mg/L). The background level of formaldehyde in the conditioning atmosphere may be reduced by increasing the rate of incoming formaldehyde-free air or by the use of carbon filters. The u
21、se of scavengers in the conditioning atmosphere is not allowed since exposing the test specimens to these chemicals could affect the rate of formaldehyde emission. 8 PROCEDURE 8.1 Desiccator preparation 8.1.1 New desiccators Thoroughly clean new desiccators and any desiccators that have been used fo
22、r purposes other than for the determination of formaldehyde. A1 Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 03 Mar 2008 5 AS/NZS 4266.16:2004 COPYRIGHT 8.1.2 Before each determination Rinse the desiccator and the glass dish (Clause 5.2) with distilled or de-ionized water and dry before each determi
23、nation. Place 300 1 mL of de-ionized or distilled water at 20 1C in the glass dish (Clause 5.2), which is centrally located at the bottom of the desiccator. Position the wire mesh support (Clause 5.3) within the desiccator above the glass dish. 8.2 Test conditions Place the desiccator on a vibration
24、-free surface in an environment that is capable of maintaining the air temperature inside the desiccator within the limits of 20 0.5C. The mean temperature during the test period shall be within the range of 20 0.2C. 8.3 Positioning of the test pieces Place the test pieces, free of any loose particl
25、es, in the wire sample holder (Clause 5.4) before putting inside the desiccator. Position the sample holder, containing the test pieces, inside the desiccator at the centre of the wire mesh support so that it is located directly above the glass dish. 8.4 Monitoring of test conditions 8.4.1 Temperatu
26、re Fit a desiccator, identical to that being used to measure the emission of the test pieces, as specified in Clause 8.1.2 but containing no test pieces, with the temperature-measuring device specified in Clause 5.5. The temperature inside the desiccator shall be monitored continuously, or at interv
27、als not exceeding 15 min, and the mean temperature during the test period shall be recorded. NOTE: Alternatively, the temperature may be monitored by locating the thermocouple in the test environment adjacent to the desiccator. 8.4.2 Background formaldehyde Measure the background formaldehyde in the
28、 testing environment by using the desiccator containing no test pieces, as described in Clause 8.4.1. 8.5 Test duration The duration of the test shall be 24 h 10 min. 8.6 Sample collection Thoroughly mix the formaldehyde solution contained in the glass dish. Rinse a 100 mL volumetric flask, as speci
29、fied in Clause 5.8, with the formaldehyde solution and then fill with the solution. Use a glass stopper to seal the volumetric flask. If the sample is not to be analysed immediately, it shall be stored at between 0C and 5C for a maximum of 30 h before analysis. The same procedure shall be followed f
30、or the measurement of background formaldehyde. 9 DETERMINATION OF FORMALDEHYDE 9.1 General The formaldehyde content of the aqueous solutions shall be determined photo-metrically by the acetylacetone method. 9.2 Principle The determination is based on the Hantzsch reaction in which the formaldehyde r
31、eacts with ammonium ions and acetylacetone to yield diacetyldihydrolutidine (DDL). DDL has an absorption maximum between 410 and 415 nm. The reaction is specific to formaldehyde. Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 03 Mar 2008 AS/NZS 4266.16:2004 6 COPYRIGHT 9.3 Procedure Pipette 25 mL of t
32、he formaldehyde solution to be analysed into a 100 mL flask (Clause 5.12), add 25 mL of the acetylacetone-ammonium acetate solution (Clause 6.2) and seal the flask with the stopper. Heat the stoppered flask for 10 min in a water bath at 65 2C. Store the solution at 20C for 1 h 5 min, protecting agai
33、nst the influence of light, before the absorbance of the solution is determined at a wavelength of 412 nm against water, using a spectrophotometer (Clause 5.6). Determine the background formaldehyde (Clause 8.4.2) using the same procedure. NOTES: 1 If maximum absorbance occurs at a wavelength other
34、than 412 nm, all measurements, including calibration, may be conducted at this wavelength. 2 Spectrophotometer cells with a path-length of at least 50 mm are recommended. 9.4 Calibration curve 9.4.1 General The calibration curve is produced from a standard formaldehyde solution, the concentration of
35、 which has been determined by iodometric titration. The calibration curve shall be checked at least once a week. It is determined using the method in Clause 9.4.2 or a suitable equivalent. 9.4.2 Formaldehyde standard solution 9.4.2.1 Reagents The following reagents shall be used: (a) Standard iodine
36、 solution, c(I2) = 0.05 mol/L. (b) Standard sodium thiosulphate solution, c(Na2S2O3) = 0.1 mol/L. (c) Standard sodium hydroxide solution, c(NaOH) = 1 mol/L. (d) Standard sulphuric acid solution, c(H2SO4) = 1 mol/L. (e) Starch solution 1%. The solutions in Items (a) to (d) above shall be standardized
37、 before use. 9.4.2.2 Procedure Dilute about 1 mL formaldehyde solution (concentration 35% to 40%) in a 1000 mL volumetric flask with water, and make up to the mark. Determine the exact formaldehyde concentration as follows: (a) Mix 20 mL of the formaldehyde standard solution with 25 mL iodine soluti
38、on and 10 mL sodium hydroxide solution. (b) After 15 min standing protected from light add 15 mL of sulphuric acid solution. (c) Titrate back the excess iodine with the sodium thiosulphate solution. (d) Near the end of the titration add some drops of the starch solution as an indicator. (e) Carry ou
39、t a blank test with 20 mL of water. 9.4.2.3 Calculation The formaldehyde content is calculated in accordance with the following equation: c(HCHO) = ()() 1000 20 OSNa15 3220 cVV Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 03 Mar 2008 7 AS/NZS 4266.16:2004 COPYRIGHT where c(HCHO) = formaldehyde conce
40、ntration, in milligrams per litre V= volume of the consumed thiosulphate titration solution, in millilitres V0= volume of the consumed thiosulphate titration solution for blank, in millilitres c(Na2S2O3) = thiosulphate concentration in mols per litre NOTE: 1 mL of 0.1 mol/L thiosulphate corresponds
41、to 1 mL of 0.05 mol/litre iodine solution and 1.5 mg formaldehyde. 9.4.3 Formaldehyde calibration solution Using the concentration value determined in Clause 9.4.2, calculate the volume of the formaldehyde solution, which will contain 3 mg formaldehyde. Transfer this volume, using a micro-burette, t
42、o a 1000 mL volumetric flask and make up to the mark with water. One litre of this calibration solution contains 3 mg formaldehyde. 9.4.4 Determination of the calibration curve The calibration curve shall be determined as follows: (a) Pipette 0, 5, 10, 20, 50 or 100 mL of formaldehyde calibration so
43、lution (Clause 9.4.3) into a 100 mL volumetric flask and make up to the mark with water. (b) Analyse 25 mL of each dilution photometrically by the procedure described in Clause 9.3. (c) Determine a blank value in parallel, using a solution made up of 25 mL distilled or de-ionized water and 25 mL ace
44、tylacetone-ammonium acetate solution, which is taken into consideration when determining the absorbance values of the calibration solutions. (d) Plot the absorbance values against the formaldehyde concentrations, c, (between 0 and 3 mg/L). (e) Determine the slope, f, of the graph, either graphically
45、 or by calculation. 9.5 Calculation of the concentration of formaldehyde in the glass crystallizing dish in the desiccator The concentration of formaldehyde in the glass crystallizing dish in the desiccator due to the test pieces shall be calculated in accordance with the following equation: G = ()
46、1800 bd S AAf where G = concentration of formaldehyde due to the test pieces, in mg/L f= slope of the calibration curve for the standard formaldehyde solution, in mg/L Ad= absorbance of the solution from the desiccator containing the test pieces Ab= absorbance of the background formaldehyde solution
47、 (see Clause 8.4.2) S= surface area of the test pieces, in cm2 (see Clause 7.3) 10 EXPRESSION OF RESULTS The emission of formaldehyde from the samples shall be measured as the quantity of formaldehyde collected in the glass dish expressed in milligrams per litre (mg/L) rounded to the nearest 0.01 mg
48、/L. Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 03 Mar 2008 AS/NZS 4266.16:2004 8 COPYRIGHT 11 TEST REPORT The test report shall contain the following: (a) Name and address of testing laboratory. (b) Sampling report according to AS/NZS 4266.1. (c) Date of the test report. (d) Reference to this Stan
49、dard, i.e., AS/NZS 4266.16. (e) Panel type, thickness, and density. (f) Date of sampling. (g) Date of formaldehyde determination. (h) Relevant product specification. (i) Surface treatment, if relevant. (j) Specific apparatus used, in case of different possibilities allowed in the Standard. (k) Test results expressed as stated in Clause 10. (l) All deviations from this Standard. Accessed by UNIVERSI