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1、BRITISH STANDARD BS 2782-6: Method 640A: 1979 ISO 2577:1975 Methods of testing Plastics Part 6: Dimensional properties Method 640A: Determination of shrinkage of test specimens in the form of bars of compression moulded thermosetting moulding materials ISO title: Plastics Thermosetting moulding mate
2、rials Determination of shrinkage of compression moulded test specimens in the form of bars IMPORTANT NOTE. Before reading this method it is essential to read the foreword, general introduction and instructions to BS 2782, issued separately. UDC 678.5/.8:678.01:536.416:620.192.52 Licensed Copy: Londo
3、n South Bank University, London South Bank University, Tue Dec 12 08:46:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6:Method 640A:1979 This British Standard, having been prepared under the direction of the Plastics Standards Committee, was published under the authority of the Executive Boa
4、rd and comes into effect on 31 August 1979 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference PLC/17 Draft for comment 78/55155 DC ISBN 0 580 10904 6 Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: London South Bank Univ
5、ersity, London South Bank University, Tue Dec 12 08:46:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6:Method 640A:1979 BSI 10-1999 i Contents Page National foreword ii 1 Scope and field of application 1 2 References 1 3 Definitions 1 4 Sampling 1 5 Test specimens 1 6 Procedure 1 7 Expressio
6、n of results 2 8 Test report 2 Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:46:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6:Method 640A:1979 ii BSI 10-1999 National foreword This British Standard has been prepared under the direction of the Plas
7、tics Standards Committee and is identical with ISO 2577 “Plastics Thermosetting moulded materials Determination of shrinkage of compression moulded test specimens in the form of bars” published by the International Organization for Standardization (ISO). The method supersedes methods 106A, 106B, 106
8、C, 106D and 106E of BS 2782:1970, which will be withdrawn after twelve months from publication of this method. Terminology and conventions. The text of the International Standard has been approved as suitable for publication, without deviation, as a British Standard. Some terminology and certain con
9、ventions are not identical with those used in British Standards; attention is especially drawn to the following. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point on the baseline as a decimal marker. Wherever the words “Internatio
10、nal Standard” appear, referring to this standard, they should be read as “British Standard”. The technical committee has reviewed the provisions of ISO 291:19771) to which reference is made in clauses 2 and 6 and has decided that they are acceptable for use in conjunction with this standard. A relat
11、ed British Standard is the foreword, general introduction and instructions to BS 2782. WARNING NOTE. This British Standard method which is identical with ISO 2577 does not necessarily detail all the precautions necessary to meet the requirements of the Health and Safety at Work etc Act 1974. Attenti
12、on should be paid to any necessary safety precautions, and the method should only be operated by trained personnel. 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 B
13、ritish Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, annside front cover, pages i and ii, pages 1 and 2 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This w
14、ill be indicated in the amendment table on the inside front cover. Cross-references International StandardCorresponding British Standard ISO 295:1974aBS 2782 Method 902A:1977 Compression moulding test specimens of thermosetting materials (Identical) a Supersedes ISO/R 295 referred to in the text. 1)
15、 Supersedes ISO/R 291 referred to in the text. Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:46:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6:Method 640A:1979 BSI 10-19991 1 Scope and field of application This International Standard specifies a me
16、thod of determining the moulding shrinkage and the shrinkage after heat treatment of thermosetting moulding materials. These characteristics are useful for the production control of thermosetting materials and for checking uniformity of manufacture. Furthermore, knowledge of the initial shrinkage of
17、 thermosetting materials is important for the construction of compression moulds, and that of post-shrinkage for establishing the suitability of the moulding material for the manufacture of moulded pieces with accurate dimensions. 2 References ISO/R 291, Plastics Standard atmospheres for conditionin
18、g and testing. ISO/R 295, Plastics Compression moulding test specimens of thermosetting materials. 3 Definitions For the purpose of this International Standard the following definitions apply: 3.1 moulding shrinkage the relative difference in dimensions between a moulding from a given material and t
19、he mould cavity in which it was moulded, both the mould and the moulding after cooling being at defined conditions when measured 3.2 post-shrinkage the relative difference between the dimensions of a moulded piece after cooling and the dimensions of the same piece after having been treated in an ove
20、n at a given temperature for a defined period and again cooled 4 Sampling A representative sample shall be taken from the moulding material to be tested and be kept at room temperature in airtight containers until moulded without any conditioning. 5 Test specimens 5.1 For determining the moulding sh
21、rinkage the test specimens to be used shall be bars with a length of not less than 80 mm, a width between 10 and 15 mm and a thickness between 4 and 10 mm. 5.2 The test specimens shall be prepared in a positive or a semipositive compression mould with single or multiple cavities. 5.3 In special case
22、s it may be suitable to engrave marks on the upper part of the mould near both ends of the specimen in order to allow an accurate measurement. 6 Procedure 6.1 If not already known, measurements of the lengths of the cavities or the distance between the engraved marks of the mould shall be made to th
23、e nearest 0,01 mm, at a temperature of 23 2 C (in accordance with ISO/R 291). The gaugings of these moulds (as well as the measurements of the test specimens) shall always be made between the same marked measuring points. These numerical values are recorded as gauges of the moulds and employed as a
24、constant for each calculation of shrinkage. NOTEFrom time to time moulds shall be checked for wear, etc. Apart from measuring directly the lengths of the cold moulds, the gauge for the moulds may be obtained very precisely by cold moulding specimens from lead and measuring the lengths of these piece
25、s. 6.2 At least three test specimens from the sample to be tested shall be moulded under such conditions of pressure, temperature, time, etc. as agreed upon by the interested parties as suitable for the material. In the absence of such agreements, moulding shall be carried out in accordance with the
26、 recommendations given in the Annexes to ISO/R 295. After removal from the mould, the test specimens shall be allowed to cool to room temperature by placing them on a material with low thermal conductivity and under an appropriate load to avoid warping. Store them at a temperature of 23 2 C and a re
27、lative humidity of 50 5 % until making measurements. 6.3 The period of storage of the test specimens for determining the moulding shrinkage shall be between 16 and 72 h. 6.4 For the determination of the moulding shrinkage, the lengths of the bars from end face to end face, or the distances between t
28、he marks on the bars, shall be measured at a temperature of 23 2 C to the nearest 0,02 mm with micrometers, screw gauges or similar devices having the same accuracy. At least three specimens are to be measured. NOTEBefore measuring the lengths of the test specimens, they shall be put on completely p
29、lane sheets of glass or metal in order to determine any warps or distortions. Test specimens with such defects must be rejected. 6.5 For the determination of the post-shrinkage, the test specimens, measured as described in 6.4, shall be supported to avoid deformation, separated from each other and p
30、ut in an oven. Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:46:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6:Method 640A:1979 2 BSI 10-1999 The heating temperatures are: 80 2 C for urea-formaldehyde moulding materials; 110 3 C for all other therm
31、osetting moulding materials. The times of exposure are: 48 1 h for rapid determination; 168 2 h for normal determination. NOTEThe post-shrinkage depends strongly on the time of exposure. Therefore the exposure time is to be noted (see 7.2 and section 8), and to be fixed in the specification of the m
32、aterial. At the end of the heating period, the test specimens shall be removed from the oven and allowed to cool in a standard atmosphere of 23 2 C and a relative humidity of 50 5 % for at least 3 h. After the cooling period the test specimens shall be measured again at a temperature of 23 2 C to an
33、 accuracy of 0,02 mm as described in 6.4. 7 Expression of results 7.1 The moulding shrinkage (MS) is given, as a percentage, by the formula 7.2 The post-shrinkage (PS) is given, as a percentage, by the formula: 8 Test report The test report shall include the following particulars: a) the grade and d
34、esignation of the moulding material; b) the type of test specimen used; c) the date of preparation of the test specimens; d) the moulding conditions by reference to the appropriate International Standard or otherwise; e) the moulding shrinkage (MS) as a percentage, including the individual values, t
35、he mean value; f) the post-shrinkage (PS48h and/or PS16h) as a percentage, including the individual values, the mean value; g) the total number of test specimens; h) the number of rejected test specimens; i) the cause for rejection, if possible with details (for example, 2 mm warp in a length of 120
36、 mm); j) the conditions of heat treatment, if different from those specified in this International Standard; k) the date of the tests. where L0is the length, in millimetres, of the dimension of the mould, determined as in 6.1; L1is the length, in millimetres, of the corresponding dimension measured
37、on the test specimen according to 6.4 where L1is the same as in 7.1; L2is the length, in millimetres, of the same dimension of the test specimen, measured after heat treatment for 48 or 168 h, according to 6.5. MS L0L1 L0 - -100= PS48h or PS168h L1L2 L1 - -100= Licensed Copy: London South Bank Unive
38、rsity, London South Bank University, Tue Dec 12 08:46:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI blank Licensed Copy: London South Bank University, London South Bank University, Tue Dec 12 08:46:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2782-6: Method 640A: 1979 ISO 2577:1975 BSI 389 Chisw
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