1、BRITISH STANDARD BS 6057-3.24: 1992 ISO 498:1992 Rubber latices Part 3: Methods of test Section 3.24 Preparation of dry films from natural rubber latex concentrate NOTEAttention is drawn to BS 6057-0 General introduction, issued separately.BS6057-3.24:1992 This British Standard, having been prepared
2、 under the directionof the Plastics and Rubber Standards Policy Committee, was published underthe authority of the Standards Board and comesintoeffect on 15 August 1992 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference PRM/51 Draft announced in BSI New
3、s, July 1992 ISBN 0 580 21087 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Plastics and Rubber Standards Policy Committee (PRM/-) to Technical Committee PRM/51, upon which the following bodies were represented: British Rubber Manufa
4、cturers Association Malaysian Rubber Producers Research Association Medical Sterile Products Association Tropical Growers Association Amendments issued since publication Amd. No. Date CommentsBS6057-3.24:1992 BSI 10-1999 i Contents Page Committees responsible Inside front cover National foreword ii
5、1 Scope 1 2 Normative references 1 3 Apparatus 1 4 Sampling 1 5 Procedure 1 List of references Inside back coverBS6057-3.24:1992 ii BSI 10-1999 National foreword This Section of BS 6057 has been prepared under the direction of the Plastics and Rubber Standards Policy Committee and is identical with
6、ISO 498:1992 Natural rubber latex concentrate Preparation of dry films, published by the International Organization for Standardization (ISO). This Section of BS 6057 supersedes clause 21 of BS 1672:1972, which will be deleted by amendment. A British Standard does not purport to include all the nece
7、ssary 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 Standard Corresponding British Standard ISO 123:1985 BS 6057 Rubber l
8、atices Part 2:1987 Sampling (Identical) ISO 124:1992 BS 6057 Rubber latices Section 3.2:1992 Determination of total solids contents of rubber latices (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 and 2, an inside back cover and a ba
9、ck 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.BS6057-3.24:1992 BSI 10-1999 1 1 Scope This International Standard specifies a method for preparing dry, homogeneous films,
10、substantially free of air bubbles, from natural rubber latex concentrate. The procedure is not necessarily suitable for latices from natural sources other than Hevea brasiliensis or for compounded latex, vulcanized latex or artificial dispersions of rubber or synthetic rubber latices. 2 Normative re
11、ferences 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
12、 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 tota
13、l solids content. 3 Apparatus 3.1 Suitable mould, in which the film can be cast, prepared by cementing strips of glass or a rigid plastic material 6 mm wide and 1,5 mm thick on a flat piece of glass plate. The cavity so formed shall be of an adequate size to provide suitable specimens for testing, e
14、.g. with sides of 100 mm to 150 mm. NOTE 1As a result of the effect of surface tension, areas of the film around the edges may be thicker than at the centre. Adhesives suitable for affixing the strips to the glass are epoxide resin adhesives, and poly(vinyl acetate) dissolved in methyl ethyl ketone.
15、 Such a mould will give dry films about 1 mm thick when filled with latex of 62 % (m/m) total solids content. 3.2 Square-mesh gauze, of polyamide or stainless steel, with an average aperture width of1804m 104m, for straining the latex. 3.3 Straightedge, wooden, plastic or stainless steel, with which
16、 to scrape the surface of the latex in the mould free of air bubbles. 3.4 Cabinet or covered space, clean, dry and dust-free, with a level surface on which to place the mould. 3.5 Oven, capable of maintaining a temperature of35 C 2 C. 3.6 Cellulosic-film sheets, thin, clear and transparent, to cover
17、 and protect the dry film. 3.7 Desiccator or airtight container, for storing the dry film. 3.8 Beaker, of suitable capacity, e.g. 50 cm 3 . 4 Sampling Carry out the sampling in accordance with one of the methods specified in ISO 123. 5 Procedure Determine the total solids content of the latex in acc
18、ordance with ISO 124. If the total solids content is less than or equal to 62 % (m/m), prepare the film without dilution of the latex. If the total solids content is greater than 62 % (m/m), add distilled water to bring it to 61,5 % (m/m) solids content. Mix the latex sample gently to ensure homogen
19、eity and allow to stand for 5 min. Strain 35 cm 3to 40 cm 3carefully through the gauze (3.2) into the beaker(3.8). Allow to stand for 5 min in the beaker. During this period, keep the beaker covered in order to minimize surface drying. Remove any bubbles from the surface of the latex in the beaker w
20、ith a piece of filter paper. Place the mould in the position in which the film will be left to dry (see 3.4). Then pour the latex into the mould in a continuous stream while moving the beaker to and fro over the surface and close to the plate to avoid the formation of air bubbles. Pour a slight exce
21、ss of latex over that required to fill the mould completely. Allow the latex in the mould to stand for 1 min, then scrape off the excess with the clean straightedge (3.3) by moving it evenly across the mould at a speed of up to 25 mm/s once only. Allow the cast film to dry in a normal, dust-free atm
22、osphere for not less than 16 h (i.e. overnight). After drying at room temperature, continue to dry the film in the oven (3.5) at a temperature of35 C 2 C. When sufficiently dry to handle, strip the film from the mould, taking care to handle the surface of the film as little as possible. Turn the fil
23、m over and place it flat on a piece of thin, clear, transparent cellulosic sheet (3.6). Allow to stand for at least another 24 h at a temperature of35 C 2 C and, when dry, cover the remaining side of the film with a similar cellulosic sheet. In some cases, the dryness of the film can be judged by it
24、s clarity. Clarity of the film generally increases as it becomes dry. If it is not possible to judge the dryness visually, dry the film to constant mass at a temperature of 35 C 2 C in a dry atmosphere. Store the dry film in the desiccator or airtight container (3.7) to prevent absorption of moistur
25、e, and keep in a cool place in the dark until required.2 blankBS6057-3.24:1992 BSI 10-1999 List of references See national foreword.BS 6057-3.24: 1992 ISO 498:1992 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing B
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