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1、BRITISH STANDARD BS 2782-4: Method 434D:1975 Methods of testing Plastics Part 4: Chemical properties Method 434D: Determination of antioxidants in polyolefin compounds by a spectrophotometric method IMPORTANT NOTE. Before reading this method it is essential to read the “Foreword, general introductio
2、n and instructions” to BS 2782, issued separately. UDC 678.5/.8:678.01 + 543.42:678.742:678.048 BS 2782-4:Method 434D:1975 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference PLC/17 Draft for comment 72/52257DC ISBN 0 580 08920 7 A British Standard does
3、not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside
4、 front cover, pages i and ii, pages 1 to 3 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No.DateComments BS 2782-4:Metho
5、d 434D:1975 BSI 12-1999i Contents Page 1Scope1 2Principle1 3Reagents1 4Apparatus1 5Test portion1 6Procedure2 7Calculation2 8Test report3 Table 1 Antioxidants which react in the method3 ii blank BS 2782-4:Method 434D:1975 BSI 12-19991 1 Scope This method describes a procedure for the determination of
6、 certain antioxidants used in polyolefin compounds by the reduction of ferric chloride and the subsequent colorimetric determination of the ferrous ions. 2 Principle This method depends upon the reducing action of the antioxidant. The antioxidant is extracted from the polymer compound and reacted wi
7、th ferric chloride solution. The concentration of the resulting ferrous ions is determined colorimetrically by the use of 2,2-bipyridyl. All the materials listed in Table 1 reduce ferric ions and may be determined by this method although the sensitivity to each antioxidant differs. Mixtures of these
8、 antioxidants cannot be differentiated by this method, but the total antioxidant present should be estimated by comparing with a reference antioxidant (see note). NOTEThe antioxidants present in the sample may first be identified by the thin layer chromatographic procedure (see Method 434A). If more
9、 than one antioxidant listed in Table 1 is found, a choice has to be made of the antioxidant to be used for calibration. For samples containing unknown antioxidants, it is convenient to calibrate with 2,6-ditertbutyl-p-cresol, i.e. the reference compound used in the t.l.c. procedure. 3 Reagents The
10、following reagents are required. 3.1 Toluene, complying with the requirements of grade 2 of BS 8051). 3.2 Industrial methylated spirits (IMS), 64 OP complying with the requirements of BS 35912). 3.3 Ethanol 99.7 % to 100 % v/v. 3.4 Ferric chloride hexahydrate, analytical reagent grade, 2 g/l solutio
11、n in ethanol. It is essential this solution is prepared and stored in an amber bottle. It is essential that this bottle is not exposed to daylight when not in use and it should be further masked by, e.g. a covering of black paper or paint. This reagent will keep for one week. 3.5 2,2-bipyridyl solut
12、ion, 5 g/l solution in industrial methylated spirits. 4 Apparatus The following apparatus is required. 4.1 Round bottom flasks, with B24/29 ground glass stoppers, 50 ml capacity. 4.2 Reflux condensers, with B24/29 joint fitted if required, with a mechanically driven stirrer. 4.3 Water bath, or heati
13、ng mantle. 4.4 Filtration apparatus 4.5 Volumetric flasks, one-mark, 100 ml capacity, Class B, complying with the requirements of BS 17923). 4.6 Water bath, capable of being maintained at 25 0.5 C. 4.7 Spectrophotometer, or absorptiometer, suitable for measurements at a wavelength of 520 nm. 4.8 Pai
14、r of 10 mm glass cells 4.9 Stopwatch 5 Test portion 5.1 For concentrations of antioxidants below 0.02 % use up to 5 g of compound. 5.2 For concentrations of antioxidants between 0.02 % and 0.20 % use approximately 1 g of compound if the antioxidant is Nonox WSP or Santonox4). For other antioxidants
15、use approximately 2 g of compound. 1) BS 805 “Toluenes”. (In the 1963 edition of BS 805, grade 2 was designated 805/3.) 2) BS 3591 “Industrial methylated spirits”. 3) BS 1792 “One-mark volumetric flasks”. 4) Trade names and chemical names are listed in Table 1. BS 2782-4:Method 434D:1975 2 BSI 12-19
16、99 5.3 For concentrations of antioxidants exceeding 0.20 % use 25 ml of toluene for the extraction in place of the 10 ml specified in 6.1 and make up the total volume of the extract to 250 ml. Use approximately 2 g of compound. 6 Procedure 6.1 Extraction. Place the requisite quantity of the polyolef
17、in compound, in the form of small pieces or shavings of not more than 2 mm thickness, in a 50 ml round bottom flask. Add 10 ml of toluene, connect the flask to a reflux condenser and heat the contents on a boiling water bath for 1 h to 1.5 h, or for such shorter time as is sufficient for the polyole
18、fin to dissolve. During this time gently swirl the contents of the flask occasionally. Where there is a possibility of incomplete extraction of the antioxidant from a polymer which is difficult to dissolve, the sample may be refluxed with mechanical stirring for 1 h, or for such shorter time as is s
19、ufficient for the polyolefin to dissolve. Apply a gentle flow of nitrogen to the flask and condenser during the extraction period. Wash down the condenser with 15 ml to 20 ml of IMS, remove the flask, stopper and shake vigorously to precipitate all dissolved polymer. When cool, filter through a fast
20、 filter paper5) into a 100 ml one-mark volumetric flask. Wash the polymer and filter with IMS until the volume of filtrate is 100 ml and shake to mix. 6.2 Colorimetry. By means of a pipette transfer 10.0 ml of the extract solution into a test tube. Similarly transfer 10.0 ml of a 1 + 9 mixture of to
21、luene and IMS to a second test tube. Place both tubes in an opaque container and add 0.5 ml of the bipyridyl reagent solution to each tube, followed by 1.0 ml of ferric chloride solution, first to the blank and then to the sample (see note). Start the stopwatch, mix the solutions, stopper the tubes,
22、 place a light-tight lid on the container and transfer to a constant temperature water bath at 25 0.5 C. After 57 1 min remove the tubes from the bath and fill the 10 mm cells, avoiding exposure to direct sunlight as much as possible. Measure the absorbance of both sample and blank after 60 1 min at
23、 a wavelength of 520 nm. 6.3 Calibration. Prepare calibration graphs by carrying out the colorimetric procedure in 6.2 on 10 ml portions of solutions of each antioxidant of known concentration. Correct each absorbance for the absorbance of the blank and plot a graph of corrected absorbance against m
24、illigrams of antioxidant per 10 ml of toluene/IMS solution. The range covered varies, e.g. 0 to 0.10 mg for Nonox WSP and Santonox. 0 to 0.35 mg for Topanol CA. NOTEScrupulous cleanliness should be observed in the use of pipettes for ferric chloride, and exposure to daylight should be kept to the mi
25、nimum. Blanks that turn pink are suspect and the test should be repeated with fresh ferric chloride solution 6.3 Calibration. Prepare calibration graphs by carrying out the colorimetric procedure described in 6.2 on 10 ml portions of solutions of each antioxidant of known concentration. Correct each
26、 absorbance for the absorbance of the blank and plot a graph of corrected absorbance against milligrams of antioxidant per 10 ml of toluene/IMS solution. The range covered varies, e.g. 0 to 0.10 mg for Nonox WSP and Santonox, 0 to 0.35 mg for Topanol CA. 7 Calculation Correct the absorbance measured
27、 for the sample for that of the blank and relate the corrected absorbance to milligrams of antioxidant per 10 ml of extract solution by reference to the appropriate calibration graph. Then 5) Whatman No. 31 is suitable. mg antioxidant/10 ml extract solution mass of sample (g) taken for test -% antio
28、xidant present= BS 2782-4:Method 434D:1975 BSI 12-19993 8 Test report Report the total percentage antioxidant present, stated with reference to a particular antioxidant. Table 1 Antioxidants which react in the method Chemical nameTrade name (see note) 2,6-ditertbutyl-p-cresolIonol CP Topanol OC (1)
29、(2) 2,4,6-tri-(3,5-ditertbutyl-4-hydroxybenzyl)mesityleneIonox 330(1) pentaerythritol tetra-3-(3,5-ditertbutyl-4-hydroxybenyl)propionateIrganox 1010(3) octadecyl-3-(3,5-ditertbutyl-4-hydroxybenyl)propionateIrganox 1076(3) NN-di-2-naphthyl-p-phenylenediamineNonox CI(2) 2,2-di-(4-hydroxy-3-methylpheny
30、l)propaneNonox DCP(2) di-2-hydroxy-5-methyl-3-(1-methylcyclohexyl)-phenyl methaneNonox WSP(2) 4,4-thiodi-(6-tertbutyl-m-cresol)Santonox(4) 4-stearamidophenolSuconox 18(5) 1,1,3-tri-(5-tertbutyl-4-hydroxy-2-methylphenyl)butaneTopanol CA(2) NOTEChemical names are in accordance with the Brussels nomenc
31、lature as given in “Classification of chemicals in the Brussels nomenclature”, Her Majestys Stationery Office for HM Customs and Excise, 1973. 1) Registered trade marks of the Shell Group of Companies. 2) Registered trade marks of Imperial Chemical Industries Ltd. 3) Registered trade marks of the Ge
32、igy Company. Ltd. 4) Registered trade mark of Monsanto Chemicals Ltd. 5) Registered trade mark of the Miles Chemical Company. BS 2782-4: Method 434D:1975 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national body responsible for preparing British
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