1、BS ISO 249:2016Rubber, raw natural Determination of dirt contentBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO 249:2016 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 249:2016. Itsupersedes BS ISO 249:2014 which is with
2、drawn.The UK participation in its preparation was entrusted to TechnicalCommittee PRI/50, Raw materials (including latex) for use in therubber industry.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all th
3、e necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016. Published by BSI StandardsLimited 2016ISBN 978 0 580 92668 6ICS 83.040.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standar
4、d was published under the authority of theStandards Policy and Strategy Committee on 31 July 2016.Amendments issued since publicationDate Text affectedBS ISO 249:2016 ISO 2016Rubber, raw natural Determination of dirt contentCaoutchouc naturel brut Dtermination de la teneur en impuretsINTERNATIONAL S
5、TANDARDISO249Fifth edition2016-07-01Reference numberISO 249:2016(E)BS ISO 249:2016ISO 249:2016(E)ii ISO 2016 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized ot
6、herwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright offic
7、eCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 249:2016ISO 249:2016(E)Foreword iv1 Scope . 12 Normative references 13 Reagents 14 Apparatus . 25 Procedure. 25.1 Preparation of the test portion . 25.2 Preparati
8、on of the peptizer 35.3 Determination . 35.4 Care of sieves 56 Expression of results 67 Precision . 68 Test report . 6Annex A (informative) Guidance for using precision results 7Annex B (informative) Precision . 8Bibliography .10 ISO 2016 All rights reserved iiiContents PageBS ISO 249:2016ISO 249:20
9、16(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which
10、 a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all mat
11、ters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This do
12、cument was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all
13、such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience of users and d
14、oes not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www
15、.iso.org/iso/foreword.htmlThe committee responsible for this document is ISO/TC 45, Rubber and rubber products, Subcommittee SC 3, Raw materials (including latex) for use in the rubber industry.This fifth edition cancels and replaces the fourth edition (ISO 249:2014), of which constitutes a minor re
16、vision with the following change: the first sentence of 5.1.1 has been corrected.iv ISO 2016 All rights reservedBS ISO 249:2016INTERNATIONAL STANDARD ISO 249:2016(E)Rubber, raw natural Determination of dirt contentWARNING Persons using this International Standard should be familiar with normal labor
17、atory practice. This International Standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.1 ScopeThis
18、International Standard specifies a method for the determination of the dirt content of raw natural rubber.It is not applicable to dirt present as surface contamination.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensabl
19、e for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 565, Test sieves Metal wire cloth, perforated metal plate and electroformed sheet Nominal sizes of openingsISO 179
20、5, Rubber, raw natural and raw synthetic Sampling and further preparative procedures3 ReagentsWARNING All recognized health and safety precautions shall be exercised during the operations of this analysis, with particular emphasis on safe handling of the flammable solvents required. All solvents sha
21、ll be free from water and dirt.During the analysis, wherever possible, use only reagents of recognized analytical grade.3.1 Mixed xylenes, boiling range 139 C to 141 C.3.2 High-aromatic hydrocarbon solvent known as white spirit, boiling range 155 C to 198 C, or other hydrocarbon solvents of similar
22、boiling range.3.3 Light petroleum, boiling range 60 C to 80 C or other hydrocarbon solvents of similar boiling range.3.4 Toluene.3.5 Rubber peptizing agents.3.5.1 Xylyl mercaptan solution, a mass fraction of 36 % in mineral oil.3.5.2 2-mercaptobenzothiazole.3.5.3 Di-(2-benzamidophenyl) disulfide. IS
23、O 2016 All rights reserved 1BS ISO 249:2016ISO 249:2016(E)3.5.4 Tolyl mercaptan solution, a mass fraction of 20 % to a mass fraction of 40 % in mineral oil.3.5.5 Other fully soluble rubber peptizing agent.4 ApparatusOrdinary laboratory equipment, and the following.4.1 Conical flask, of capacity 250
24、cm3or 500 cm3fitted with a suitable stopper; or beaker, of capacity 250 cm3or 500 cm3, and a clock glass of appropriate diameter as cover.4.2 Short air condenser, (optional).4.3 Thermometer, reading to at least 200 C.4.4 Heater, for heating the conical flask or beaker (4.1) and its contents (see 5.3
25、.4).Hotplates which provide uniform heating surfaces, or infrared lamps, are recommended. Infrared lamps (250 W) can be placed in rows, with the base of the conical flask about 20 cm from the top of the lamp. Individual control of each lamp is recommended to prevent localized overheating. Alternativ
26、ely, a sand bath may be used.4.5 Sieve, of nominal size of openings 44 m to 45 m (325 mesh) of corrosion-resistant wire gauze, preferably stainless steel, complying with ISO 565.4.5.1 The wire gauze shall be mounted across the end of a metal tube about 25 mm in diameter and greater than 20 mm long.4
27、.5.2 The sieve shall be constructed in such a way that the gauze is free from distortion and is protected from accidental damage. A suitable construction is shown in Figure 1.4.5.3 Sieves and holders may also be constructed by removing the bottom of a metal crucible having the appropriate dimensions
28、, and soldering the screen to the crucible. This results in an ample container for the rubber solution during filtering.4.5.4 A coarse screen may also be soldered under the 44 m to 45 m (325 mesh) gauze to protect it from accidental damage. This “guard” screen shall not hinder the filtration in any
29、way but only provide a support for the gauze.4.5.5 Commercially available filtration apparatus having 44 m to 45 m (325 mesh) gauze is acceptable, provided it can be used as specified in this International Standard.4.6 Ultrasonic equipment, for cleaning sieves (4.5) (optional but desirable).5 Proced
30、ure5.1 Preparation of the test portion5.1.1 Prepare a homogenized laboratory sample of raw natural rubber in accordance with ISO 1795. From the homogenized laboratory sample, take about 30 g, and pass it twice between the cold rolls of a laboratory mill, the nip being adjusted to 0,5 mm 0,1 mm by me
31、ans of a lead strip (see ISO 2393).12 ISO 2016 All rights reservedBS ISO 249:2016ISO 249:2016(E)5.1.2 Immediately weigh a test portion of 10 g to 20 g to the nearest 0,1 g. (For “clean” rubbers of low dirt content, a 20 g test portion is recommended. For heavily contaminated rubbers, a smaller test
32、portion should be used.)5.1.3 Carry out the determination in duplicate.5.2 Preparation of the peptizer5.2.1 If xylyl mercaptan (3.5.1) is used, use 1 g of the solution per test portion and 150 cm3to 230 cm3of solvent (3.1 or 3.2).5.2.2 If 2-mercaptobenzothiazole (3.5.2) or di-(2-benzamidophenyl) dis
33、ulfide (3.5.3) is used, use 0,5 g per test portion. Prepare a solution by dissolving 0,5 g of solid in 200 cm3of solvent (3.1 or 3.2) and filtering off any insoluble material.5.2.3 If tolyl mercaptan (3.5.4) is used, use 1 g to 1,5 g of the solution per test portion and 200 cm3of solvent (3.1 or 3.2
34、).5.3 Determination5.3.1 To the conical flask or the beaker (4.1), add solvent and peptizer according to 5.2.1, 5.2.2, and 5.2.3.5.3.2 Cut the test portion into pieces, each of mass about 1 g, and drop each piece, separately, into the flask or beaker containing solvent (5.3.1).5.3.3 Heat the flask o
35、r beaker and its contents (see 4.4) at 125 C to 130 C until a smooth solution is obtained, or stopper the flask or cover the beaker with a clock glass and stand for several hours at room temperature before heating to 125 C to 130 C. A short air condenser (4.2) can be used during the heating, to redu
36、ce evaporation of the solvent. ISO 2016 All rights reserved 3BS ISO 249:2016ISO 249:2016(E)1a2bcd 39,7 31,8 29,450,8 30,2 25,4+0,20+0,20 27,80-0,23,21,214,37,14,8204,84,850,895,2 9,511,1M8 27,8 27,8Key1 sieve (stainless sieve ring with wire gauze soldered on to it)2 sieve holder (stainless steel or
37、brass cylinder)aA recess of 1 mm around the inner edge of the top and the outer edge of the lower end is allowed for easy stacking of the sieves.bDimensions: 30 mm external diameter, 2 mm to 3 mm wall thickness, and 3 mm height.cBraze on outside.dSieve holder for inspection of sieve.Figure 1 Details
38、 of suitable sieve and holder for dirt determination4 ISO 2016 All rights reservedBS ISO 249:2016ISO 249:2016(E)5.3.4 Agitate the flask or beaker occasionally by hand.Boiling or overheating of the rubber solution can result in the formation of a gel-like substance which renders subsequent filtration
39、 difficult and can result in a higher apparent dirt content; hence, avoid apparatus and conditions which can cause local overheating.5.3.5 When the rubber is completely dissolved (and the solution is adequately mobile), decant the hot solution through the sieve (4.5), which has been weighed to the n
40、earest 0,1 mg, retaining the bulk of the dirt in the flask or beaker.5.3.6 Wash the flask or beaker and the retained dirt with hot solvent (3.1 or 3.2) until the rubber has been completely removed. Again, retain the bulk of the dirt in the flask or beaker. (About 100 cm3of hot solvent is normally re
41、quired for effective washing.) During the later stages of the washing operation, rinse the dirt from the flask or beaker into the sieve. Loosen any dirt adhering to the flask or beaker with a glass rod, so it can be rinsed on to the sieve.5.3.7 Remove any gelled rubber which will not pass through th
42、e sieve by one of the following methods:a) gently brushing the underside of the gauze with a small sable brush while hot solvent remains in the sieve;b) standing the sieve in a beaker containing about 10 mm depth of toluene (3.4) and gently boiling for 1 h, covering the beaker with a clock glass.The
43、se operations should preferably be carried out under a hood.5.3.8 Wash the sieve twice, either with light petroleum (3.3), in which case dry at 100 C for 30 min, or with white spirit (3.2), in which case dry at 100 C for 1 h.5.3.9 The dirt on the sieve after drying should be loose and, apart from fi
44、brous matter, be free-flowing. It should be readily dislodgeable from the wire gauze. If this is not so, treat the sieve with boiling toluene as in 5.3.7 b).5.3.10 If gelled rubber still remains, abandon the determination and carry out a repeat determination.5.3.11 Cool the sieve and residue in a de
45、siccator and weigh to the nearest 0,1 mg.5.4 Care of sieves5.4.1 At all stages, handle the sieve carefully. Inspect it after each determination to check for damage, for example under a microscope, with a slide projector (to throw an image of the gauze on a screen) or with magnifying glass (10). If n
46、oticeable distortion of the wire gauze has occurred, replace it with new gauze.5.4.2 After each determination, remove loose dirt by careful brushing. Partially blocked sieves can usually be cleaned by boiling in xylene, but more effectively with ultrasonic equipment (4.6). If, in spite of this treat
47、ment, the gauze is badly blocked and the mass of the sieve has increased more than 1 mg, replace the wire gauze.5.4.3 Sieves can be stored in warm toluene (3.4) to lessen build-up of rubber. ISO 2016 All rights reserved 5BS ISO 249:2016ISO 249:2016(E)6 Expression of resultsThe dirt content, expresse
48、d as a percentage by mass, of the test portion is given by Formula (1):mm10100 (1)wherem0is the mass, in grams, of the test portion;m1is the mass, in grams, of the dirt.Express the result to the nearest 0,01 %.7 PrecisionSee Annex B.8 Test reportThe test report shall contain the following informatio
49、n:a) a reference to this International Standard, i.e. ISO 249;b) all details necessary for identification of the sample;c) the mean of the two results;d) the solvent and peptizer used;e) any particular points observed in the course of the test;f) any operation not specified in this International Standard or in the International Standards to which reference is made, and any operation regarded as optional.6 ISO 2016 All rights reservedBS ISO 249:2016ISO 249:2016(E)Annex A (informative) Guidance for
