1、BRITISH STANDARD This Standard is confirmed.See the BSI Catalogue for details. August 1997. BS 7164-12: 1991 ISO 2453:1991 Incorporating Technical Corrigendum No. 1 Chemical tests for raw and vulcanized rubber Part 12: Determination of bound styrene content of raw styrene-butadiene rubber, emulsion
2、polymerized: refractive index method ICS.83.040.10 BS 7164-12:1991 This British Standard, having been prepared under the direction of the Plastics and Rubber Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 31 October 1991 BSI 28 November
3、2003 The following BSI references relate to the work on this standard: Committee reference PRM/23 Draft for comment 84/38407 DC ISBN 0 580 20156 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Plastics and Rubber Standards Policy Commi
4、ttee (PRM/-) to Technical Committee PRM/23, upon which the following bodies were represented: Institute of Water and Environmental Management Laboratory of the Government Chemist Ministry of Defence Royal Society of Chemistry Rubber and Plastics Research Association Amendments issued since publicati
5、on Amd. No. Date Comments 14801 Technical Corrigendum No. 1 28 November 2003 Change to Table 1BS 7164-12:1991 BSI 28 November 2003 i Contents Page Committees responsible Inside front cover National foreword ii 1S c o p e 1 2 Significance of the test 1 3 Principle 1 4R e a g e n t s 1 5A p p a r a t
6、u s 1 6 Preparation of test pieces 2 7 Procedure 3 8 Expression of results 3 9 Test report 4 Annex A (informative) Other International Standards relating to the styrene content of styrene-butadiene rubbers 6 Table 1 Values of refractive index at 25 C and percentage, by mass, of bound styrene 5BS 716
7、4-12:1991 ii BSI 28 November 2003 National foreword This part of BS 7164 has been prepared under the direction of the Plastics and Rubber Standards Policy Committee and is identical with ISO 2453:1991 “Rubber, raw styrene-butadiene, emulsion-polymerized Determination of bound styrene content Refract
8、ive index method”, including Technical Corrigendum August 2003, published by the International Organization for Standardization (ISO). BS 7164 rationalizes all the methods that deal with chemical analysis of raw, compounded and vulcanized rubber, some of which have previously been published in BS 90
9、3, BS 1673 and BS 5923. Relevant parts of those standards will be withdrawn or deleted by amendment, as appropriate, when superseded by Parts and Sections of BS 7164. This part of BS 7164 supersedes BS 1673-5.1:1963 which is withdrawn. Annex A of this standard is for information only. Cross-referenc
10、es The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British St
11、andards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front co
12、ver, an inside front cover, pages i and ii, pages 1 to 7 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued.BS 7164-12:1991 BSI 28 November 2003 1 1 Scope This International Standard specifies a method for determining the bound styrene c
13、ontent of emulsion-polymerized styrene-butadiene (SBR) rubbers by correlation with the measured refractive index of an extracted sample according to a table of refractive indices versus percentages by mass of styrene. The method is also applicable to extracted oil-extended emulsion-polymerized SBR a
14、s long as it produces a film suitable for refractive index measurements. It is not applicable to solution-polymerized SBR. 2 Significance of the test The bound styrene test is a measure of the bound monomeric composition of the rubber. It is used as a check on the accuracy of monomer charging and al
15、so as a guide to the uniformity of the product, since the bound styrene content affects the physical properties. 3 Principle Extraction of a test piece with ethanol-toluene azeotrope (ETA), followed by drying and pressing between sheets of aluminium foil to provide sheeted rubber having a thickness
16、of not more than 0,50 mm. Calculation of the bound styrene content from the refractive index obtained at 25 C on this thinly sheeted rubber. 4 Reagents 4.1 Ethanol-toluene azeotrope (ETA) Mix 7 volumes of absolute ethanol with 3 volumes of toluene. Alternatively, mix 7 volumes of commercial grade et
17、hanol with 3 volumes of toluene, and boil the mixture with anhydrous calcium oxide (quicklime) under reflux for 4 h. Then distil the azeotrope and collect the fraction with a boiling range not exceeding 1 C, for use in the test. 4.2 Acidified ETA Add 10 cm 3of concentrated hydrochloric acid approxim
18、ately 35 % (m/m) to a portion of ETA (4.1) and make the solution up to 1 000 cm 3with ETA. NOTE 1 Acidified ETA is used for alum-coagulated polymers. 4.3 -Bromonaphthalene 5 Apparatus 5.1 Spiders, consisting of 13 mm squares of sheet aluminium or stainless steel having a nickel-chromium wire leg abo
19、ut 38 mm long attached to each corner. When the extracting solvent is ETA acidified with hydrochloric acid, the spider and the legs shall be made of tantalum. 5.2 Reflux condenser 5.3 Abbe-type refractometer, having fourth-decimal-place accuracy and whose refracting prism can be placed in a nearly h
20、orizontal position for measurement of the refractive index of solids. An Amici-type compensating prism for achromatization is necessary unless a sodium-vapour lamp is used as a light source. The refractometer shall be maintained at a temperature of 25 C0 , 1 C, obtained by the use of a constant temp
21、erature room or by circulating constant temperature water through the instrument. 5.4 Vacuum oven, capable of being evacuated to a pressure of 1 300 Pa 1)and of maintaining a temperature of 100 C5 C. 5.5 Aluminium foil, between 0,025 mm and 0,08 mm thick, having good tear strength. 5.6 Glass referen
22、ce, for checking adjustment of the refractometer. The glass reference shall be calibrated for use at 25 C. 1) 10 3 Pa = 10 3 N/m 2 = 7,5 mmHg.BS 7164-12:1991 2 BSI 28 November 2003 5.7 Hydraulic press, that can be maintained at a temperature of 100 C and can attain a total force of up to 100 kN on t
23、he platens. 5.8 Pressing plates, (optional apparatus), measuring 210 mm 210 mm 3 mm, with a wooden handle. One of the plates shall have a 150 mm square area in the centre milled out to a depth not to exceed 0,65 mm. 5.9 Scissors, small and sharp. 5.10 Light source, which shall be collimated to provi
24、de a beam at grazing incidence to the prism. If an incandescent light source is used, such as a flashlight bulb, it shall be of low intensity. A sodium-vapour lamp may also be used. The light source requirement is that a clear, sharp line with good contrast can be observed in the telescope of the re
25、fractometer. Attenuation or diffusion of the light for better viewing may be accomplished by placing crumpled tissue paper in the light path. 6 Preparation of test pieces 6.1 Sheet out the rubber to a thickness of no greater than 0,5 mm. Cut the sheeted rubber into strips approximately 13 mm wide an
26、d 25 mm long. Fasten one strip to each leg of the spider (5.1), thus allowing each portion of the rubber to be contacted on all sides by the solvent. Place the spider and strips in a40 0cm 3flask into which 60 cm 3of ETA have been placed (for alum-coagulated polymers, use acidified ETA and tantalum
27、spiders). Fit the reflux condenser (5.2) in position. Extract for 1 h at a temperature at which the solvent boils gently. Replace the solution with another 60 cm 3of ETA or acidified ETA and extract for an additional hour, remove the spider from the flask and dry the rubber to constant mass in the v
28、acuum oven (5.4), maintained at a pressure of about 1 300 Pa and a temperature of 100 C5 C. It is important that the test pieces be extracted and dried thoroughly since either residual solvent or incompletely extracted materials will result in erroneous readings of the refractive index. NOTE 2 Avoid
29、 plasticizing of the sample by overheating. 6.2 After the test pieces have been thoroughly dried, remove them from the spiders. At this point, more than one technique is suitable for pressing the test piece. The method of pressing may be modified to suit the type of rubber and the type of equipment
30、available. The pressure and the time of pressing at 100 C may be varied. The test piece may be cooled to room temperature under pressure, or removed from the press while hot. The time of hot pressing shall never exceed 10 min, and should preferably be 5 min. The conditions shall be chosen so that th
31、e pressed test piece is homogeneous and so that a distinct line can be observed dividing the light and dark fields of the telescope field when the refractive index is determined. Two general techniques are given for the pressing operation, in 6.2.1 and 6.2.2. 6.2.1 If pressing plates (5.8) are used,
32、 proceed as follows. Place approximately 0,3 g of the dry extracted polymer between two sheets of aluminium foil about 50 mm square and fold the corners over once. Place this test piece between the pressing plates and place the plates in the press held at 100 C. Close the platens without applying pr
33、essure and preheat for 1 min. Several test pieces may be pressed at one time. Apply a force of about 100 kN for 3 min. Release the pressure, remove the test pieces from the press and allow them to cool. 6.2.2 If the pressing is to be done between flat platens without a cavity, proceed as follows, mo
34、difying the details of the procedure to suit the sample. Prepare approximately 25 mm squares of the clean aluminium foil. Place a portion of one of the dried strips between two pieces of foil. Press the test piece between the foil squares with a force of between 2,2 kN and 6,6 kN at 100 C for from 3
35、 to 10 (preferably 3 to 5) min. If several test pieces are pressed at one time, increase the applied force proportionally so that the pressure on each test piece is between about 3,45 MPa and 10,35 MPa. Forces lower than the usual limit may be necessary for some polymers. It may also be necessary, w
36、ith some polymers, to allow the pressed test pieces to cool under pressure while cooling the platens with cold water. 6.3 The thickness of the final test piece to be measured shall not exceed 0,5 mm and may be much thinner. The ability to handle the pressed test piece and obtain a good refractive in
37、dex reading are the only requirements with respect to test piece thickness.BS 7164-12:1991 BSI 28 November 2003 3 6.4 Cut the prepared test piece in half with sharp scissors (5.9) and peel off one piece of the foil. Cut off a strip about 6 mm wide by 12 mm long with the scissors, in such a way that
38、one of the narrower ends is freshly cut. The second piece of foil may be removed but it is frequently easier to handle the test piece with one foil piece left on the rubber. 7 Procedure 7.1 Check that the temperature of the refractometer has stabilized at 25 C. 7.2 Check the adjustment of the refrac
39、tometer by means of the glass reference (5.6) pressed firmly against the prism, using a drop of -bromonaphthalene (4.3) as contact liquid. The small light source (5.10) shall be collimated and the best readings are obtained with the glass reference if the light is diffused through crumpled tissue pa
40、per. Move the hand control until the boundary line just reaches the cross-hairs (always moving from the light into the dark field). Make at least three readings. Adjust the instrument to give the reading of the glass reference. After this adjustment, clean the prism well with ethanol and a lens pape
41、r. 7.3 Place the test piece on the prism with the cut edge toward the light source approximately where the glass reference was positioned. Remove the tissue paper from the light source. Press the test piece firmly on the prism with a finger and wait 1 min for temperature equilibrium. It is also perm
42、issible to close the upper prism on the test piece lightly if adequate light can still be focused on the end of the test piece, but unless the test piece is very thin this operation can damage the prism or its mounting. Adjust the compensating prism until a sharp dividing line between the light and
43、dark fields, with minimum colour, is obtained. Test the contact between rubber and prism by pressing the test piece against the prism. There shall be no change in the position of the boundary line during this test. 7.4 Make at least three readings. If the readings differ by more than 0,0001, further
44、 readings are necessary. 7.5 Repeat the process of obtaining readings with another portion of the test piece having a freshly cut edge. Average the mean values of the two sets of readings thus obtained. If the two mean values do not differ by more than 0,000 2, use this average for the calculation i
45、n accordance with Clause 8. If the difference is more than 0,000 2, the procedure shall be repeated. If necessary, correct the refractive index measurement to 25 C using the following equation: n 25 = n + 0,00037( 25 ) 8 Expression of results 8.1 Method of calculation The bound styrene content, w s
46、, of the styrene-butadiene rubber, expressed as a percentage by mass, is determined from the refractive index, corrected to 25 C, by using Table 1 or the following equation: w s = 23,50 + 1 164(n 25 1,534 56) 3 497(n 25 1 , 5 345 6) 2 8.2 Precision 8.2.1 Repeatability 95 % of the results shall not d
47、iffer from the mean by more than 0,5 % (m/m) when the bound styrene content is in the range of 20 % (m/m) to 30 % (m/m). 8.2.2 Reproducibility The reproducibility is of the same order of magnitude as the repeatability for SBR polymerized at 50 C. The reproducibility for SBR polymerized at 5 C is not
48、 known exactly, but it is thought to be within the above repeatability limits, when testing polymers in the 20 % (m/m) to 30 % (m/m) styrene region. where n 25 is the refractive index at 25 C; n is the refractive index at temperature of measurement ; is the temperature of measurement, in degrees Cel
49、sius.BS 7164-12:1991 4 BSI 28 November 2003 9 Test report The test report shall include the following particulars: a) a reference to this International Standard; b) all details necessary for the complete identification of the sample; c) the results and the method of expression used; d) any unusual features noted during the determination; e) any operation not included in this International Standard, or any operation regarded as optional.BS 7164-12:1991 BSI
