1、INTERNATIONAL STANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEXAYHAPOAHAR OPrAHM3AMR n0 CTAHAAPTM3AMM Rubber - Determination of total sulfur content - Part 3 : Furnace combustion method Caoutchouc - Dosage du soufre total - Partie 3 : Mkthode pa
2、r combustion au four Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 6528-3 : 1888 (El Foreword IS0 (the International Organization for Standardization) is a worldwid
3、e federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that
4、 committee. International organizations, govern- mental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Eiectrotechnical Commission (IECI on all matters of electrotechnical standardization. Draft International Standards adopted b
5、y the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the IS0 Council. They are approved in accordance with IS0 procedures requiring at least 75 % approval by the member bodies voting. International Standard IS0 5528-3 was p
6、repared by Technical Committee ISO/TC 45, Rubber and rubber products, Users should note that all International Standards undergo revision from time to time and that any reference made herein to any other International Standard implies its latest edition, unless otherwise stated. 0 lnternatlonal Orga
7、nlration for Standardization, 1988 0 Printed in Switzerland Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INTERNATIONAL STANDARD IS0 6528-3 : 1988 (E) Rubber - Determin
8、ation of total sulfur content - Part 3 : Furnace combustion method 0 Introduction Parts 1 and 2 of IS0 6528 give alternative methods for the determination of the total sulfur content of rubber. 1 Scope and field of application 1.1 This part of IS0 6528 specifies a method for the deter- mination, by
9、combustion in a furnace, of the total sulfur con- tent of raw rubbers, unvulcanized compounded rubbers and vulcanizates, including sulfur present as barium sulfate, calcium sulfate and lithopone. 1.2 It is applicable to chlorinated rubbers, nitrile rubbers and hydrocarbon rubbers (including natural
10、rubber). The deter- mination is not affected by the presence of metal salts which form insoluble sulfates. 2 References IS0 383, Laboratory glassware - Interchangeable conical ground joints. IS0 4793, Laboratory sintered lfrittedl filters - Porosity grading, classification and designation. IS0 6528,
11、 Rubber - Determination of total sulfur content - Part I : Oxygen combustion flask method. - Part 2 : Sodium peroxide fusion method. 3 Principle 3.1 A test portion is burnt in a stream of oxygen in the presence of a catalyst, the oxides of sulfur are passed into hydrogen peroxide and the resulting s
12、ulfuric acid is determined by titration. 3.2 One of two titration methods is used, depending on the type of rubber combusted. An alkalimetric titration is used when no chlorine or nitrogen combustion products are present and a barium perchlorate titration is used when chlorine and/or nitrogen is pre
13、sent. All recognized health and safety precautions shall be observed when carrying out this method of analysis. 4 Reagents During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Reagents for the combu
14、stion 4.1.1 Calcium chloride, anhydrous, particle size approxi- mately 600 to 1 400 ym (14 to 22 mesh ASTM). 4.1.2 Catalyst. Mix together 0,8 g of dry vanadium pentoxide and 0,2 g of zinc oxide for each determination. The vanadium pentoxide shall be previously dried by heating in a shallow dish at 1
15、40 to 160 “C for 16 h. It shall be cooled and stored in a desiccator. 4.1.3 Hydrogen peroxide, 3 % (V/V) solution. Carefully mix 1 volume of 30 % hydrogen peroxide with 9 volumes of water. WARNING - 30 % hydrogen peroxide is very corrosive to the skin. Wear rubber or plastic gloves and goggles when
16、handling it. 4.1.4 Magnesium perchlorate, anhydrous, particle size 600 to 1 400 Mm (14 to 22 mesh ASTM). WARNING - Magnesium perchlorate can cause irri- tation of skin and mucous membranes. 4.1.5 Supply of oxygen, e.g. a cylinder with suitable regulator to give a pressure of not less than 35 kPa. 4.
17、1.6 Carbon dioxide absorbent (sodium hydroxide ab- sorbed on synthetic silicate), particle size 600 to 1 400 pm (14 to 22 mesh ASTM), preferably of the self-indicating type. 1 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction
18、 or networking permitted without license from IHS-,-,-4.2 Reagents for titration 4.2.1 Perchloric acid, dilute solution. Carefully mix. 1 volume of 50 % perchloric acid (HCIOS sol- ution with 1 volume of water. WARNING - Perchloric acid should be handled with ex- treme caution. Contact with dust or
19、organic particles may, in many cases, cause ignition. Contact with organic materials must be avoided. 4.2.2 bPropanol. Use m-distilled P-propanol if analytical grade reagent is not available. 4.2.3 Barium perchlorate, standard volumetric solution, c Ba(Cl04)21 = 0,Ol mol/dms. 4.2.3.1 Preparation Dis
20、solve 3,363 g of barium perchlorate in 208 cmsof water. Ad- just the pH to about 3,5 with the dilute perchloric acid (4.2.1). Make up to 1 dms with the Zpropanol (4.2.2). 4.2.3.2 Standardization Standardize the barium perchlorate by weighing, to f 0,l mg, approximately 0,lO g anhydrous sodium sulfat
21、e and dissolving it in 10 cm3 of water in a 100 cm3 one-mark volumetric flask. Make up to the mark with water. Pipette exactly 10 cm3 of this solution into a small flask or beaker, add 46 cm3 of the Bpropanol to make the solution 80 % alcohol by volume and titrate to the same end-point as will be us
22、ed in the analysis of rubbers, using the same indicator system (see 7.2). Determine the molar concentration, cl, of the barium per- chlorate solution, expressed in moles of Ba(C10412 per cubic decimetre, from the formula 0,l x m, x 1000 142,06 x I, where m, is the mass, in grams, of sodium sulfate;
23、V, is the volume, in cubic centimetres, of barium per- chlorate required for the titration. 4.2.3.3 Storage Preparations of barium perchlorate deteriorate on storage and should be standardized often enough to detect a change in concentration of 0,600 5 mol/dms. 4.2.4 Sodium hydroxide solution, c(NaO
24、H) = 0,02 mol/dms, accurately standardized or com- mercial solution. 4.2.5 Indicator systems for barium perchlorate titrations. Two systems are given, both suitable for use in this part of IS0 6528. 4.2.5.1 Thorin indicator. Dissolve 0,2 g of Thorinlr in 100 cm3 of water. The reagent shall be a unif
25、orm red powder and produce a clear orange aqueous solution. 4.2.5.2 Thorin and methylene blue indicator. Dissolve 0,5 g of Thorin in 100 cm3 of water. Dissolve 0,012 g of solid methylene blue in 100 cm3 of water. 4.2.6 Indicator system for alkalimetric titration. Dissolve 0,125 g of methyl red and 0
26、,04 g of methylene blue in 106 cm3 of methanol. 4.2.7 Hydrochloric acid, cIHCI) = 2 mol/dma. Dilute 1 volume of hydrochloric acid (Q = 1,18 Mg/ms) with 5 volumes of water. 4.2.8 Cation exchange resin, strongly acidic, containing nuclear sulfonic acid active groups9 Before filling the column (5.6) al
27、low the resin to stand in a beaker of distilled water to absorb water and become swollen. Check that the following requirements are fulfilled before use and after regeneration (because of the large capacity of the resin to remove interfering cations, it may be used five to ten times before regenerat
28、ion becomes necessary) : a) IO cm3 of sulfuric acid solution, c (H2SO4) = 0,02 moVdm3, shall be completely eluted with 15 cm3 of water; test the last portion of the eluate for the absence of sulfate using Thorin solution (4.2.5.1); b) the ion exchange column shall be capable of removing 0,l g of zin
29、c, which is the most commonly interfering cation in rubber analyses. 1 J Thorin is 2,2-hydroxy-3,6-disuIfo-l-naphthyl-azobenzene-arsonic acid. 2) There are many types and particle size ranges of resin available. DOWEX 5OW-8X spheres 75 to 156 urn (100 to 200 mesh) from J.T. Baker Company, 222 Red Sc
30、hool Lane, Phillipsburg, New Jersey668 65, USA, has been found satisfactory. This information is given for the convenience of users of this part of IS0 6528 and does not constitute an endorsement by IS0 of the product named. Equivalent products may be used if they can be shown to lead to the same re
31、sults. 2 Copyright International Organization for Standardization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 6526-3 : 1966 (EI Regenerate the resin by passing 10 cmsof the hydrochloric acid 5.1.7 Electric combustion fu
32、rnace with temperature in- (4.2.7) through the resin bed, at the rate of 2 or 3 drops per second, then wash the resin bed with 20 cm3 of water at a dicator and controller (HI, about 320 mm long, capable of maintaining a temperature of 1 000 * 20 OC. faster rate. Test the last few drops of the washin
33、gs for the absence of sulfate using Thorin solution (4.2.5.1). 5.2 Absorption train. 5 Apparatus 5.2.1 Primary absorbing vessel (J) (see figure 2). Ordinary laboratory apparatus, glassware having joints comply- ing with the requirements of IS0 383, and 5.1 Combustion apparatus (see figure 1). 5.1.1
34、Flowmeter (AI, to indicate 0,8 to 1 cm%. 5.1.2 Purifying train, consisting of two U-tubes (B and C) with side arms, connected to the calibrated flowmeter (A). 5.1.2.1 U-tube (B), with side arms, contains the magnesium perchlorate (4.1.4). 5.1.2.2 U-tube (C), with side arms, contains the carbon diox-
35、 ide absorbent (4.1.6). 5.1.3 Silica combustion tube, with heater for bent-end (D). The total horizontal length is 650 to 670 mm. It consists of a satin or transparent silica tube of 16 mm internal diameter fused at one end to a transparent silica tube, which narrows to 7 mm internal diameter. The o
36、ther end is fused to a 24/29 cone provided with hooks. The overall measurement across the 24129 cone and hooks shall not exceed 30 mm. The length of the wide tube is 480 mm; the narrower tube is horizontal for 170 to 190 mm and then bends downwards at a right angle and continues for a further 77 mm,
37、 including a IO/19 cone with hooks in the same plane as the bend. The cone is greased with sulfur-free high-temperature-resisting silicone grease. To pre- vent condensation of vapour in the bent-end of the combustion tube and in the neighbouring ground glass joint, the bent portion is electrically h
38、eated to a temperature of 460 to 500 OC which is controlled by suitable means. The 24/29 cone is fitted with a socket provided with hooks, and this is connected by rubber tubing to the U-tube (C) of the purifying train. This is in the shape of a U-tube and is joined to the combustion tube by a IO/19
39、 socket which is 70 to 80 mm (measured ver- tically) from the bottom of the U-tube. The internal diameter of this limb is 6 mm and the stopcock is 30 to 35 mm from the bot- tom of the tube. A sintered glass disc (porosity grade P 40, see IS0 4793), diameter 30 mm, is sealed in the other limb at the
40、lower end of the expanded portion, which is 70 mm long and 30 mm in diameter. This limb then narrows to 14 mm diameter for 30 mm and terminates in a 12/13 socket. 5.2.2 Secondary absorbing vessel (K). This consists of a 20 or 25 cm3 pear-shaped flask with a IO/19 socket at the neck and side arm. The
41、 side arm is fitted with a IO/19 cone and delivery tube which is connected via a calcium chloride tube (L) to a needle valve (M) and suction line. The two absorbing vessels are connected to each other by an in- verted U-tube of 7 mm internal diameter with a 12/13 cone at one end and a IO/19 cone and
42、 delivery tube at the other end. The delivery tube ends not more than 1 mm from the bottom of the secondary vessel. All ground glass joints of the absorption train are secured by springs and no grease is used. 5.2.3 Calcium chloride tube (LI. 5.2.4 Needle valve (Ml. 5.3 Burette, 10 cm3 capacity, rea
43、ding to 0,Ol ems, 5.4 Magnetic stirrer, (desirable, but not essential). 5.5 Daylight matching lamp (desirable, but not essential), A screen of heat-resistant, thermally insulating material is fixed at the exit end of the combustion tube so that radiated heat from the furnace does not affect the solu
44、tions in the absorbing vessels. 5.1.4 Silica rod with handle and button (E). The diameter of the rod shall be 7 to 8 mm and the diameter of the button 12 to 13 mm. The overall length is 125 mm. 5.1.5 Magnetic stainless steel cylinder IF). The diameter is 5.6 Ion-exchange column, comprising a small t
45、ube, about 170 mm long with an internal diameter of IO mm, provided with a stopcock or sintered glass disc at one end. The bottom shall be filled to a depth of about 10 mm with glass wool, and the rest of the column shall be filled with the resin (4.2.8). 6 Preparation of test sample 13 to 14 mm, th
46、e length 10 to 11 mm. Also, a magnet capable of moving the cylinder (F) from outside the silica combustion tube (D) is required. 6.1 Finely mill the test sample on a laboratory roll mill and thoroughly homogenize it. 5.1.6 Combustion boat (transparent silica) with handle (G). Outside measurements :
47、overall length 53 to 55 mm, width 11 to 13 mm and depth 7 to 9 mm. 6.2 Due to the small masses of the test portions, the rubber shall be protected from contamination. The use of forceps for handling the test portion reduces the risk of contamination. 3 Copyright International Organization for Standa
48、rdization Provided by IHS under license with ISONot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IS0 6528-3 : 1988 (El 7 Procedure 7.1 Combustion 7.1.1 Heat the combustion furnace (5.1.7) to 1 000 f 20 X and the bent-end of the combustion tube (5.1.3) to 400 to 500
49、oc. 7.1.2 Place a layer of about 0,3 g of the catalyst (4.1.2) in the previously ignited combustion boat (5.1.6). Weigh accurately about 50 -t- 0,l mg (IO Z!I 0,l mg in the case of ebonite or thioplastsl of the test sample and distribute this test portion in the prepared boat. Cover the test portion with the remainder of the catalyst. 7.1.3 Connect the absorbing vessels (5.2.1 and 5.2.2) to the combustion tube, remove the inverted U-tube and from a graduated pipette add 15 cm3 of the hydrog
