1、BRITISH STANDARD BS2782-6: Method640A: 1979 ISO2577:1975 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 materia
2、ls 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 BS2782, issued separately. UDC678.5/.8:678.01:536.416:620.192.52BS2782-6:Method 640A:1979
3、This British Standard, having been prepared under the directionof the Plastics StandardsCommittee, was published under the authorityofthe Executive Boardand comes into effect on 31August1979 BSI10-1999 The following BSI references relate to the work on this standard: Committee reference PLC/17 Draft
4、 for comment78/55155DC ISBN 0 580 10904 6 Amendments issued since publication Amd. No. Date of issue CommentsBS2782-6:Method640A: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 Exp
5、ression of results 2 8 Test report 2BS2782-6:Method 640A:1979 ii BSI 10-1999 National foreword This British Standard has been prepared under the direction of the Plastics Standards Committee and is identical with ISO2577 “Plastics Thermosetting moulded materials Determination of shrinkage of compres
6、sion moulded test specimens in the form of bars” published by the International Organization for Standardization (ISO). The method supersedes methods106A,106B,106C,106D and106E of BS2782:1970, which will be withdrawn after twelve months from publication of this method. Terminology and conventions. T
7、he text of the International Standard has been approved as suitable for publication, without deviation, as a British Standard. Some terminology and certain conventions are not identical with those used in British Standards; attention is especially drawn to the following. The comma has been used thro
8、ughout 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 “International Standard” appear, referring to this standard, they should be read as “British Standard”. The technical committee has reviewed the provisi
9、ons of ISO291:1977 1)to which reference is made in clauses2 and6 and has decided that they are acceptable for use in conjunction with this standard. A related British Standard is the foreword, general introduction and instructions to BS2782. WARNING NOTE. This British Standard method which is identi
10、cal with ISO2577 does not necessarily detail all the precautions necessary to meet the requirements of the Health and Safety at Work etc Act1974. Attention should be paid to any necessary safety precautions, and the method should only be operated by trained personnel. A British Standard does not pur
11、port 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. Summary of pages This document comprises a front cover, annside front co
12、ver, pagesiandii, pages1 and 2 andabackcover. 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. Cross-references International Standard Corresponding British Standard ISO295:1974 a BS
13、2782 Method 902A:1977 Compression moulding test specimens of thermosetting materials (Identical) a Supersedes ISO/R295referred to in the text. 1) Supersedes ISO/R291 referred to in the text.BS2782-6:Method640A:1979 BSI 10-1999 1 1 Scope and field of application This International Standard specifies
14、a method 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 shrinkag
15、e of 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/R291, Plastics Standard atmospheres for conditio
16、ning and testing. ISO/R295, 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
17、 the 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 o
18、ven 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
19、shrinkage the test specimens to be used shall be bars with a length of not less than80mm, a width between10 and15mm and a thickness between4 and10mm. 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 cases it m
20、ay 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 the near
21、est0,01mm, at a temperature of23 2 C (inaccordance with ISO/R291). 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 constant fo
22、r 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 pieces. 6.2 At l
23、east 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 recommendat
24、ions given in the Annexes toISO/R295. 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 of23 2 C and a relative humidity
25、 of50 5% until making measurements. 6.3 The period of storage of the test specimens for determining the moulding shrinkage shall be between16 and72h. 6.4 For the determination of the moulding shrinkage, the lengths of the bars from end face to end face, or the distances between the marks on the bars
26、, shall be measured at a temperature of23 2 C to the nearest0,02mm 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 plane sheets of glass or
27、 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 in6.4, shall be supported to avoid deformation, separated from each other and put in an oven.BS2782-6:M
28、ethod 640A:1979 2 BSI 10-1999 The heating temperatures are: 80 2 C for urea-formaldehyde moulding materials; 110 3 C for all other thermosetting moulding materials. The times of exposure are: 48 1h for rapid determination; 1682h for normal determination. NOTEThe post-shrinkage depends strongly on th
29、e time of exposure. Therefore the exposure time is to be noted (see7.2 and section8), and to be fixed in the specification of the material. At the end of the heating period, the test specimens shall be removed from the oven and allowed to cool in a standard atmosphere of23 2 C and a relative humidit
30、y of50 5% for at least3h. After the cooling period the test specimens shall be measured again at a temperature of23 2 C to an accuracy of0,02mm as described in6.4. 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,
31、as a percentage, by the formula: 8 Test report The test report shall include the following particulars: a) the grade and designation 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 appropria
32、te International Standard or otherwise; e) the moulding shrinkage (MS) as a percentage, including the individual values, the mean value; f) the post-shrinkage (PS 48hand/or PS 16h ) as a percentage, including the individual values, the mean value; g) the total number of test specimens; h) the number
33、 of rejected test specimens; i) the cause for rejection, if possible with details (for example,2mm warp in a length of120mm); j) the conditions of heat treatment, if different from those specified in this International Standard; k) the date of the tests. where L 0 is the length, in millimetres, of t
34、he dimension of the mould, determined as in6.1; L 1 is the length, in millimetres, of the corresponding dimension measured on the test specimen according to6.4 where L 1 is the same as in7.1; L 2 is the length, in millimetres, of the same dimension of the test specimen, measured after heat treatment
35、 for48 or168h, according to6.5. MS L 0 L 1 L 0 -100 = PS 48hor PS 168h L 1 L 2 L 1 -100 =blankBS2782-6: Method640A: 1979 ISO2577:1975 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents t
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