1、Wood-based panel products Determination of formaldehyde release by the flask method English version of DIN EN 717-3 DIN - EN 717-3 EUROPEAN STANDARD NORME EUROPENNE EUROPKISCHE NORM EN 717-3 March 1996 ICs 70.060.20 Descriptors: Wood-based panel products, testing, formaldehyde release. English versi
2、on Wood-based panels Determination of formaldehyde release Part 3: Formaldehyde release by the flask method Panneaux base de bois: dtermination du dgagement de formaldhyde. Partie 3: Dgagement de forrnaldhyde par la mthode au bocal Holzwerkstoffe; Bestimmung der Form- aldehydabgabe. Teil 3: Formalde
3、hyd- abgabe nach der Flaschen-Methode This European Standard was approved by GEN on 1995-12-22. CEN members are bound to comply with the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-da
4、te lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the
5、 responsibility of a GEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands,
6、Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-IO50 Brussels O 1996. CEN -All rights of exploitation in any form and by any means rese
7、rved worldwide for CEN national members. Ref. No. EN 717-3:1996 E Page 2 EN 717-311996 Contents Page 1 Scope 3 2 Normative references . 3 3 Principle 3 4 Reagents 3 5 Apparatus . 3 6 Test pieces 4 7 Procedure . 5 8 Expression of results . 7 9 Testrepor 7 Foreword This European Standard has been prep
8、ared by Technical Committee CENTTC 11 2 “Wood-based panels“ , the secretariat of which is held bv DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September 1996, and conflicting national stan
9、dards shall be withdrawn at the latest by September 1996. This standard is one of a series which specifies methods for determining formaldehyde potential in or formalde- hyde release from wood-based panels. The other standards in this series are: EN 120 Wood-based panels - Determination of formaldeh
10、yde content - Extraction method called the perforator method EN 717-1 Wood-based panels - Determination of formaldehyde release - Part 1 : Formaldehyde release by the chamber method i EN 717-2 Wood-based panels - Determination of formaldehyde release - Part 2: Formaldehyde release by the gas analysi
11、s method No existing European Standard is superseded. According to the CENICENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany. Greece, Iceland, Ireland, Italy
12、, Luxemburg, Netherlands, Norway, Portugal, Spain, Sweden, Switzer- land and the United Kingdom. Introduction The principle of the flask method for measuring the formaldehyde release has been published by Wilhelm- Klauditz-Institute (Roffael 1975). Thereafter, the method has been modified in differe
13、nt ways by many authors in several countries. After consideration of published work focusing on the method and its reliability, a temperature of 40 C and a period of 3 h have been selected for this standard. ) At present at the draft stage Page 3 EN 71 7 -3 1996 1 Scope This European Standard specif
14、ies a method, known as the flask method, for determination of formaldehyde release from uncoated wood-based panels. 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate pl
15、aces in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard, only when incorporated in it by amendment or revision. For undated references the latest edition of the publication re
16、ferred to applies. EN 322 Wood-based panels - Determination of moisture content EN 323 Wood-based panels - Determination of density EN 326-1 Wood-based panels - Sampling, cutting and inspection - Part 1: Sampling and cutting of test pieces and expression of test results 3 Principie Formaldehyde rele
17、ase is determined by suspending test pieces of known mass over water in a closed container, maintained at a constant temperature. Formaldehyde released from the test pieces during a defined period of time is absorbed by the water. The formaldehyde content of the water is determined photometrically b
18、y the acetylacetone method, and the result is expressed in milligrammes formaldehyde per kilogramme of dry board. 4 Reagents 4.1 General Reagents of recognized analytical purity and distilled or demineralised water (referred to below as distilled water) shall be used for the analysis. 4.2 Acetyiacet
19、one of anaiytical grade 4.3 Ammonium acetate of analytical grade NOTE: Commercially prepared reagents may be used, provided it can be shown that they give an equivalent result. 5 Apparatus 5.1 Test apparatus Test apparatus consisting of the following main components: 5.1.1 Polypropylene, or polyethy
20、lene flask-container of type 1 or 2 (see figures 1 and 2) of 500 mP volume with tighfiy fitting lid of the same material. 5.1.2 Metal test piece holder or rubber band and hook. Metal parts shall be of stainless steel (see figures 1 and 2). Page 4 EN 717-311996 5.2 Laboratory equipment 5.2.1 Waterbat
21、h, capable of maintaining a temperature of i40 f 1) OC 5.2.2 Cells with a suitable path length for the spectrophotometer 5.2.3 Volumetric flasks 1 O00 me (calibrated at 20 OC) 5.2.4 Volumetric flasks 100 mP (calibrated at 20 OC) 5.2.5 Flasks 50 mP (with stoppers) 5.2.6 Bulb pipettes (calibrated at 2
22、0 OC), 5 mf, 10 mt. 15 mt, 20 me, 25 me. 50 mt. 100 5.2.7 Erlenmeyer flask 250 mP 5.2.8 Microburette 5.2.9 Burette 50 mP, graduated in 0,05 mP (calibrated at 20 OC) 5.2.10 Stop watch 5.2.1 1 Balance, scale interval 0,001 g 5.2.12 Ventilated drying oven capable of maintaining a temperature of 103k2)
23、OC. 5.2.13 Ventilated oven (maximal volume: 60 I), capable of maintaining a temperature of (40+1) OC at any position in the oven. 5.2.14 Spectrophotometer capable of measuring absorbance at 41 2 nm 6 Test pieces 6.1 Sampling Test pieces of 25 mm x 25 mm x board thickness shall be taken according to
24、EN 326-1, evenly distributed over the width of the (cooled) board, but excluding a 500 mm wide strip at either end of the board. 6.2 Test pieces for the determination of the moisture content Take 12 test pieces for the determination of the moisture content. 6.3 Test pieces for the determination of t
25、he flask volume Take a sufficient number of test pieces to obtain approximately 1 O0 g of board for determining the flask value (FJ. Determine the mass of the test pieces to the nearest 0.01 g. The number of test pieces for each set has to be chosen so that their total mass is as near as possible to
26、 20 g. In case of doubt the total mass should be preferably below 20 g. The test pieces shall be cut immediately after the board has been cooled. After cutting the test pieces shall be stored, hermetically sealed, at room temperature. for comparative reasons the time elapsing between cutting and tes
27、ting should be kept as constant as possible, but shall not exceed 72 h. Page 5 EN 717-311996 7 Procedure 7.1 Determination of moisture content Determine the moisture content in accordance with EN 322. Determine the moisture content in duplicate on two samples of at least 4 test pieces. 7.2 Determina
28、tion of formaldehyde release Determinations shall always be made on duplicate sets of test pieces. The individual values shall only differ from each other by a maximum of 20 % related to the higher of two single values. Otherwise a third determination shall be carried out. Fix the test pieces face t
29、o face in the clip and attach the clip to the lid of the container, using the hook as shown in figure 1 or fix the test pieces with a rubber band as shown in figure 2. Add 50 mP of distilled water at 20 OC to the container using a bulb pipette, attach the lid with the suspended test pieces and close
30、 the container so that it is completely airtight. The bottom surfaces of the test pieces should be approximately 40 rnm above the surface of the water. A second container shall be prepared in the same way. Insert the closed containers into the oven (see 5.2.1 3) at temperature of (40f 1) OC. This te
31、mperature shall be maintained throught the whole test period. The containers shall occupy less than 10 % of the whole volume of the oven, that means not more than one container per 6 I of oven volume in order to avoid fluctuation in the temperature. The containers shall be placed staggered and with
32、a distance of at least 50 mm between each other. After (1 80 * 1) min remove the containers from the oven and immediately take off the lids with the test pieces attached. Transfer the solution from the containers to each of the two 50 mP flasks, close them tightly and allow the contents to cool at a
33、mbient temperature to approximately 20 OC. 7.3 Determination of formaldehyde concentration of the aqueous solution 7.3.1 General The formaldehyde content of the aqueous solution shall be determined photometrically. 7.3.2 Principle The determination is based on the Hantzsch reaction in which aqueous
34、formaldehyde reacts with ammonium ions and acetylacetone to yield diacetyldihydrolutidine (DOL). ODL has an absorption maximum at 41 2 nm. The reaction is specific to formaldehyde. NOTE: Other suitable photometric procedures may also be used. 7.3.3 Reagents 7.3.3.1 Acetylacetone solution 4 ml acetyl
35、acetone are added to 1 O00 mP volumetric flask and made up to the mark with distilled water. 7.3.3.2 Ammonium acetate solution 200 g ammonium acetate are dissolved with distilled water in a 1 O00 mP volumetric flask and made up to the mark. Page 6 EN 717-311996 7.3.4 Procedure 10 mP are taken from t
36、he aqueous solution (see 7.2) with a pipette (5.2.6) and added to 10 me acetylacetone solution (7.3.3.1) and 10 mP ammonium acetate solution (7.3.3.2) in a 50 mP flask (5.2.5). lhe flask is stoppered, shaken and warmed for 15 min in a water bath (5.2,.1) of (40i 1 I OC. The now greenish-yellow solut
37、ion is cooled to room temperature protected from light (about 1 hi. lhe absorbance of this solution is determined at a wavelength of 41 2 nm against distilled water using a spectrophotometer (5.2.14). A blank test shall be made with distilled water, the blank value shall be taken into consideration
38、in the determinations of the flask value (FJ. 7.3.6 Calibration curve (see figure 31 7.3.5.1 General A calibration curve is produced from a standard formaldehyde solution, the concentration of which has been determined by iodometric titration. The calibration curve shall be checked at least once a w
39、eek. 7.3.5.2 Formaldehyde standard solution Reagents: - Standard iodine solution c (I2) = 0,05 moll! - Standard sodium thiosulphate solution c (Na,S,O,) = O, 1 mo110 - Standard sodium hydroxide solution c (NaOHi = 1 mollP - Standard sulphuric acid solution c (H,SO,) = 1 molle The above solutions sha
40、ll be standardized before use. - starch solution 1 % mlm Dilute about 2.5 g formaldehyde solution (concentration 35 % to 40 %) in a 1 O00 mt volumetric flask with distilled water and make up to the mark. Determine the exact formaldehyde concentration as follows: Mix 20 mP of the formaldehyde standar
41、d solution with 25 mP iodine solution and 1 O ml sodium hydroxide solution. After 15 min standing protected from light add 15 mP of sulphuric acid solution. Tritrate back the excess iodine with the sodium thiosulphate solution. Near the end of the tritration add some drops of the starch solution as
42、an indicator. Carry out in parallel a blank test with 20 mP of distilled water. Calculate the formaldehyde content as follows: c (HCHO) = (V, - V) x 15 x c (Na,S,O,) x 1 000120 where c HCHO) is the formaldehyde concentration, in milligramms per litre V is the volume of the thiosulphate titration sol
43、ution, in millilitres VO is the volume of thiosulphate titration for the blank, in millilitres c iNa,S,O,i is the concentration of sodium thiosulphate solution. in mols per litre NOTE: 1 ml 0,l moll! thiosulphate solution corresponds to 1 mP 0,05 molle iodine solution and 1,5 mg f orrnaldehyde Page
44、7 EN717-3:1996 7.3.5.3 Formaldehyde calibration solution Using the concentration determined in 7.3.5.2, calculate the volume of the formaldehyde solution which will contain 15 mg formaldehyde. Transfer this volume, using a microburette (5.2.81, to a 1 O00 m4 volumetric flask (5.2.3) and make up to t
45、he mark with distilled water. 1 ml of this calibration solution contains 15 pg formaldehyde. 7.3.5.4 Determination of the calibration curve Pipette either zero, 5, 10, 20, 50 or 100 mP of formaldehyde calibration solution (see 7.3.5.3) into a 100 mP volumetric flask (5.2.4) and make up to the mark w
46、ith distilled water. 10 mP of each dilution is analysed photometrically by the same procedure as described in (7.3.4). The absorbance values are plotted against the formaldehyde concentrations (c) (between O and 0.01 5 mg/mP). The slope (f) of the graph is determined either graphically, or calculate
47、d (see figure 3). 8 Expression of results 8.1 Moisture content The moisture content H shall be calculated according to EN 322. 8.2 Flask value (F,) The amount of formaldehyde absorbed in 10 mP of solution from the containers is determined spectrophoto- metrically as described under 7.3.4. The flask
48、value (F,) in milligrammes per kilogramme of oven-dry board is calculated by the following equation: (A,-A,)f5010(100+H) F, = m (2) where: As AB f H m is the absorbance of the analysed solution from the containers is the absorbance of an analysis with distilled water is the slope of the calibration
49、curve, in milligrammes per millilitre is the moisture content of the test pieces, in percent is the mass of the test pieces, in grammes 9 Test report The test report shall be issued in accordance with EN 326-1. Additionally, the test report shall include the following information: - Type of board; - Density of the board according to EN 323, in kilogrammes per cubic metre; - Information regarding age, finishing, sanding etc.; - Date of formaldehyde determination; - Moisture content, in percent, at the time of testing; - Flask value (F,) in milligrammes Der kilogramme
