BS-6057-3.1-1996 ISO-35-1995.pdf

BRITISH STANDARD BS 6057-3.1: 1996 ISO 35:1995 Rubber latices Part 3: Methods of test Section 3.1 Determination of mechanical stability of natural rubber latex concentrate ICS 83.040.10 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:24:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.1:1996 This British Standard, having been prepared under the direction of the Sector Board for Materials and Chemicals, was published under the authority of the Standards Board and comes into effect on 15 June 1996 © BSI 10-1999 First published August 1990 Second edition June 1996 The following BSI references relate to the work on this standard: Committee reference PRI/51 Draft announced in BSI News February 1996 ISBN 0 580 25610 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee, PRI/51, Latex, upon which the following bodies were represented: British Rubber Manufacturers Association Ltd. Malaysian Rubber Producers Research Association Medical Sterile Products Association Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:24:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.1:1996 © BSI 10-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope1 2Normative references1 3Definition1 4Principle1 5Reagents1 6Apparatus1 7Sampling2 8Procedure2 9Expression of results2 10Test report2 List of referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:24:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.1:1996 ii © BSI 10-1999 National foreword This Part of BS 6057 has been prepared by Technical Committee PRI/51 and is identical with ISO 35:1995 Latex rubber, natural, concentrate Determination of mechanical stability, published by the International Organization for Standardization (ISO). It supersedes BS 6057-3-3.1:1990 which is withdrawn. The Technical Committee has reviewed the provisions of ISO 3310-1:1990 to which normative reference is made in the text, and has decided that is is acceptable for use in conjunction with this standard. A related British Standard to ISO 3310-1:1990 is BS 410 Specification for test sieves. 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. Cross-references International StandardCorresponding British Standard BS 6057 Rubber latices ISO 123:1985Part 2:1987 Sampling Part 3: Methods of test ISO 124:1992Section 3.1:1992 Determination of total solids content of rubber latices (Identical) ISO 125:1990Section 3.3:1990 Determination of alkalinity of natural rubber latex concentrate (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 and 2, an inside back cover 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. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:24:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI © BSI 10- © BSI 10-19991 WARNING Persons using this International Standard should be familiar with normal laboratory practice. This 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 Scope This International Standard specifies a method for the determination of the mechanical stability of natural rubber latex concentrate. It is also applicable to prevulcanized natural rubber latex concentrate. The method is not necessarily suitable for latices preserved with potassium hydroxide, latices from natural sources other than Hevea brasiliensis, or for compounded latex, or artificial dispersions of rubber, and is not applicable to synthetic rubber latices. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 123:1985, Rubber latex Sampling. ISO 124:1992, Rubber latices Determination of total solids content. ISO 125:1990, Natural rubber latex concentrate Determination of alkalinity. ISO 3310-1:1990, Test sieves Technical requirements and testing Part 1: Test sieves of metal wire cloth. 3 Definition For the purposes of this International Standard, the following definition applies. 3.1 natural rubber latex concentrate natural rubber latex containing ammonia and/or other preservatives and which has been subject to some process of concentration 4 Principle A test portion of latex concentrate is diluted to 55 % (m/m) total solids content and stirred at high speed. The time required to initiate visible flocculation is recorded, this being regarded as a measure of the mechanical stability. 5 Reagents The ammonia solutions (5.1 and 5.2) shall be prepared from ammonium hydroxide of recognized analytical reagent quality and shall be stored in closed containers. Carbonate-free distilled water or water of equivalent purity shall be used wherever water is specified. 5.1 Ammonia solution, containing 1,6 % (m/m) of ammonia (NH3), for use with latex concentrate having an alkalinity of at least 0,30 % (with respect to the latex concentrate). 5.2 Ammonia solution, containing 0,6 % (m/m) of ammonia (NH3), for use with latex concentrate having an alkalinity of less than 0,30 % (with respect to the latex concentrate). 6 Apparatus 6.1 Mechanical stability measuring apparatus1), consisting of the items described in 6.1.1 to 6.1.3. 6.1.1 Latex container, flat-bottomed, cylindrical, at least 90 mm high, with an internal diameter of 58 mm ± 1 mm and a wall thickness of approximately 2,5 mm. The inner surface shall be smooth. A poly(methyl methacrylate) or glass container is suitable. 6.1.2 Stirring apparatus, consisting of a vertical stainless steel shaft of sufficient length to reach to the bottom of the latex container (6.1.1) and tapering to approximately 6,3 mm in diameter at its lower end where an exactly centered, horizontal, smooth, stainless steel disc, 20,83 mm ± 0,03 mm in diameter and 1,57 mm ± 0,05 mm thick, is attached. The apparatus shall maintain stirring at a rotational frequency of 14 000 rev/min ± 200 rev/min throughout a test, at which frequency the shaft shall not run out of true by more than 0,25 mm. 1) Suitable instruments are available commercially, e.g. from Klaxon Ltd., Warwick, Tyseley, Birmingham, B11 2HB, United Kingdom; telefax +44 121 708 1220. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:24:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.1:1996 2 © BSI 10-1999 6.1.3 Holder, for the latex container (6.1.1). The holding arrangement shall ensure that the axis of the rotating shaft is concentric with that of the latex container and that the bottom of the stirring disc is 13 mm ± 1 mm from the inner surface of the bottom of the latex container. 6.2 Means of heating Use either a water bath, capable of maintaining a temperature of 60 °C to 80 °C, or a glass tube, bent to a shape suitable for insertion in the latex concentrate together with a means of circulating water at a temperature of 60 °C to 80 °C through the tube. 6.3 Wire cloth, stainless steel, in accordance with ISO 3310-1, with an average aperture width of 180 4m ± 7,6 4m. 7 Sampling Carry out sampling in accordance with one of the methods specified in ISO 123. NOTE 1Mechanical stability may be adversely affected by the duration and temperature of storage of the sample. 8 Procedure Carry out the determination in duplicate and within 24 h of first opening the sample bottle. If the total solids content and alkalinity of the latex concentrate are not known, determine them in accordance with ISO 124 and ISO 125, respectively. NOTE 2If the concentration of the carbon dioxide in the atmosphere in the vicinity of the mechanical stability measuring apparatus (6.1) is above normal about 0,03 % (V/V), the mechanical stability time of the latex will be reduced. This effect may be pronounced at carbon dioxide concentrations as low as 0,05 % (V/V). High carbon dioxide concentrations in the atmosphere may be caused by the proximity of any apparatus which generates carbon dioxide, such as certain gas heaters or oil heaters. Dilute 100 g of latex concentrate, in a glass beaker, to 55,0 % (m/m) ± 0,2 % (m/m) total solids content with the appropriate ammonia solution (5.1 or 5.2). Without delay, warm the diluted latex with gentle stirring to 36 °C to 37 °C (i.e. slightly above the test temperature) by one of the means of heating (6.2). Immediately filter the diluted and warmed latex through the wire cloth (6.3) and weigh 80,0 g ± 0,5 g of the filtered latex into the container (6.1.1). Check that the temperature of the latex is 35 °C ± 1 °C. Place the container in position and stir the latex, ensuring that the rotational frequency of the stirrer is 14 000 rev/min ± 200 rev/min throughout the test, until the end-point is passed. The arrival of the end-point is preceded by a marked decrease in the depth of the vortex around the stirring shaft. Determine the end-point by removing a drop of the latex with a clean glass rod at intervals of 15 s and gently spreading the sample on a suitable surface, for example the palm of the hand, a glass microscope slide, the surface of water or the stainless steel wire cloth (6.3). Take the end-point as the first appearance of flocculum. Confirm the end-point by the presence of an increased amount of flocculum in a sample taken after stirring the latex for an additional 15 s. 9 Expression of results Express the mechanical stability time of the latex concentrate as the number of seconds between the beginning of stirring and the end-point. The results of the duplicate determinations shall agree to within 5 % of their mean value. If they do not, the test shall be repeated. 10 Test report The test report shall include the following particulars: a) all details necessary for the identification of the test sample; b) a reference to this International Standard; c) the mechanical stability time of the latex concentrate, quoted to the nearest 15 s; d) the method used to detect the end-point (i.e.palm, microscope slide, water or wire cloth); e) any unusual features noted during the determination; f) details of any operation not included in this International Standard or in the International Standards to which reference is made, as well as details of any optional operation. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:24:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6057-3.1:1996 © BSI 10-1999 List of references See national foreword. 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