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1、BRITISH STANDARD BS 2782-4: Method 434B: 1977 Methods of testing Plastics Part 4: Chemical properties Method 434B: Determination of antioxidants in polyolefin compounds by ultra-violet absorption of the chloroform extract IMPORTANT NOTE. Before reading this method it is essential to read the forewor
2、d, general introduction and instructions to BS 2782, issued separately. UDC 678.5/.8:678.01:543.422.6:678.742:678.048 Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-4:Method 434B:1977 This British Stan
3、dard, having been prepared under the direction of the Plastics Standards Committee, was published under the authority of the Executive Board on 30 September 1977 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference PLC/17 Draft for comment 76/53229 ISBN 0
4、 580 09556 8 A British Standard does 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 docume
5、nt comprises a front cover, an inside front cover, pages i and ii, pages 1 and 2 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 publicatio
6、n Amd. No.Date of issueComments Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-4:Method 434B:1977 BSI 10-1999i Contents Page 0Introduction1 1Scope1 2References1 3Principle1 4Reagent1 5Apparatus1 6Test
7、portion1 7Procedure1 8Expression of results2 9Test report2 Table 1 Antioxidants which it is known may be estimated in certain polyolefins2 Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy:
8、 London South Bank University, London South Bank University, Tue Dec 12 08:42:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-4:Method 434B:1977 BSI 10-19991 0 Introduction Method 434B is one of a series of methods described in BS 2782 for determining the antioxidants in polyolefin compounds.
9、The other methods which have been published are Method 434A which deals with the identification of antioxidants by thin layer chromatography, Method 434C which describes a method of determining the antioxidants by ultra-violet absorption of the toluene ethanol extract and Method 434D which describes
10、 a method in which the antioxidant reduces iron from the ferric to the ferrous state and the latter is determined colorimetrically by the use of 2,2-bipyridyl. This method assumes that the identity of the antioxidant is known and that it is the only one present in the polyolefin under test. 1 Scope
11、This method describes a procedure for the determination of certain antioxidants in polyolefin compounds by measuring the ultra-violet absorbance of a chloroform extract of the compound. 2 References The following standards publications are referred to in this method. BS 572, Interchangeable conical
12、ground glass joints. BS 700, Graduated pipettes. BS 1792, One-mark volumetric flasks. BS 2734, Boiling flasks (narrow-necked), conical, flat bottom and round bottom. BS 2761, Spherical ground glass joints. BS 2782, Methods of test for plastics Foreword, general introduction and instructions: 1975 Me
13、thod 434A:1975 The identification of antioxidants and ultra-violet absorbers in polyolefin compounds by thin layer chromatography Method 434C:1977 Determination of antioxidants in polyolefin compounds by ultra-violet absorption of the toluene ethanol extract Method 434D:1975 Determination of antioxi
14、dants in polyolefin compounds by a spectrophotometric method. BS 3787, Glass condensers with standard joints. 3 Principle The ultra-violet absorbance of a chloroform extract of the polyolefin compound is measured over the range 250 nm to 320 nm and the concentration of antioxidant is determined from
15、 a previously prepared calibration curve. 4 Reagent The following reagent is required. It shall be of analytical reagent quality. 4.1 Chloroform 5 Apparatus The following apparatus is required. 5.1 Reflux extraction apparatus, consisting of a 150 ml round bottom flask complying with the requirements
16、 of BS 2734, fitted with a ground glass joint complying with the requirements of BS 572 or BS 2761, and a condenser complying with the requirements of BS 3787. 5.2 One-mark volumetric flasks, 100 ml, complying with the requirements of BS 1792. 5.3 Water bath or electric hotplate or heating mantle. 5
17、.4 Pipette, graduated, 10 ml capacity, complying with the requirements of BS 700. 5.5 Pair of matched fused quartz absorption cells of 10 mm (or 25 mm if appropriate) path length, fitted with stoppers or covers. 5.6 Ultra-violet spectrophotometer1) 6 Test portion Weigh to the nearest 0.01 g between
18、1 g and 5 g of the test sample depending on the expected antioxidant content. For polypropylene finely divide the sample. 7 Procedure 7.1 Extraction. Place the test portion in the extraction flask and add 60 ml of the chloroform (4.1). Boil gently under reflux for 2 h in the case of polypropylene an
19、d 1 h in the case of polyethylene. Allow the reflux apparatus to cool and wash down the condenser and the neck of the flask with about 15 ml of chloroform. Stopper the flask and leave to cool to room temperature in a bath of cold water. 1) The Hilger Uvispek or Uviscan and the Unicam SP 500 or SP 18
20、00 are suitable. Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-4:Method 434B:1977 2 BSI 10-1999 Filter the extract through a filter paper2) and collect the filtrate in a 100 ml one-mark volumetric fla
21、sk. Wash the flask and the residue on the filter paper until the volume in the flask is 100 ml. 7.2 Blank determination. Carry out the same procedure as in 7.1 but without the addition of the test portion. 7.3 Calibration. Add respectively to a series of 100 ml one-mark volumetric flasks 0, 1, 2, 3,
22、 5, 7 and 10 ml of a standard 0.10 % solution of the appropriate antioxidant in chloroform and make up to the mark with chloroform. Mix each of the solutions well and measure the absorbance over the range 250 nm to 320 nm against the blank as a comparison. Measure the absorbance at the peak height t
23、aken from a base line drawn tangentially to the curve at 255 nm and 300 nm, and plot a graph of absorbance against milligrams of antioxidant per 100 ml of chloroform solution. 7.4 Measurement of absorbance. Measure the absorbance of the extract of the test portion using a 10 mm cell (or a 25 mm cell
24、 if the antioxidant has a low concentration) using the other cell with the blank as a comparison. Carry out measurements over the range 250 nm to 320 nm. If a recording instrument is not available take measurements at the wavelengths of maximum absorbance for the individual antioxidants as given in
25、Table 1 and at 5 nm intervals between 250 nm and 300 nm and plot a graph. Measure the absorbance at the peak height taken from a base line drawn tangentially to the curve at 255 nm and 300 nm. NOTETable 1 gives a list of antioxidants which it is known may be estimated at the wavelengths given for th
26、e polyolefins shown. Compare the shape of the curve with those of the calibration samples (see 7.3). In tests on aged or reprocessed material, a marked difference in shape may indicate the presence of oxidized forms of the antioxidant. These will be included in the result by this method. Residual an
27、tioxidant alone may be determined by Method 434D. 8 Expression of results Read off from the calibration graph of absorbance against antioxidant concentration, the number of milligrams of antioxidant in 100 ml of extract and calculate the percentage of antioxidant in the test sample using the followi
28、ng equation: 9 Test report The test report shall include the following particulars. a) Complete identification of the material tested including type, source, manufacturers code numbers, previous history, etc. b) A reference to this British Standard method, i.e. BS 2782:Method 434B. c) The identity o
29、f the antioxidant and the percentage in the material tested. Table 1 Antioxidants which it is known may be estimated in certain polyolefins 2) A Whatman no. 542 filter paper is suitable. where Cis the number of milligrams of antioxidant in 100 ml of extract, and Mis the mass of test portion in grams
30、. Antioxidant %() C M - 1 10 - -= AntioxidantPolyolefinWavelength 1,1,3-tri-(5-tertbutyl-4-hydroxy-2-methylphenyl)butane 2,6-ditertbutyl-p-cresol 2,4,6-tri-(3,5-ditertbutyl-4-hydroxybenzyl)mesitylene octadecyl 3-(3,5-ditertbutyl-4-hydroxyphenyl)propionate tri-(4-nonylphenyl)phosphite Polyethylene an
31、d polypropylene Polyethylene and polypropylene Polypropylene Polypropylene Polypropylene (nm) 286 283 283 282 272 Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:42:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI blank Licensed Copy: London South Bank Universit
32、y, London South Bank University, Tue Dec 12 08:42:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-4: Method 434B: 1977 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK
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