1、BRITISH STANDARD BS 2782-9: Method 940B: 1989 ISO 2557-2: 1986 Methods of testing Plastics Part 9: Sampling and test specimen preparation Method 940B: Preparation of test specimens of amorphous thermoplastics with a specified reversion by injection moulding rectangular plates ISO title: Plastics Amo
2、rphous thermoplastics Preparation of test specimens with a specified reversion Part 2: Plates IMPORTANT NOTE. Before reading this method it is essential to read BS 2782-0, Introduction, issued separately. UDC 678.073:620.115BS2782-9:Method940B:1989 This British Standard, having been prepared under t
3、he directionof the Plastics StandardsCommittee, was published under the authority ofthe Board of BSI and comes into effect on 28February1989 BSI 12-1999 First published December1981 First revision February1989 The following BSI references relate to the work on this standard: Committee reference PLM/
4、17 Draft for approval for publication announced in BSI News April1988 ISBN 0 580 16888 3 Amendments issued since publication Amd. No. Date of issue CommentsBS2782-9:Method940B:1989 BSI 12-1999 i Contents Page National foreword ii 1 Scope and field of application 1 2 References 1 3 Definitions 1 4 Mo
5、ulding conditions 1 5 Design and shape of the plate 2 6 Injection mould 2 7 Preparation of test specimens 2 8 Test report 3 Figure 1 Test specimen with rectangular test plate 4 Figure 2 Test bars cut length- or crosswise 5 Publications referred to Inside back coverBS2782-9:Method940B:1989 ii BSI 12-
6、1999 National foreword This method has been prepared under the direction of the Plastics Standards Committee and is identical with ISO2557-2 “Plastics Amorphous thermoplastics Preparation of test specimens with a specified reversion Part2: Plates”, published in1986 by the International Organization
7、for Standardization (ISO). It is a revision of BS2782:Method 940B:1981, which was identical with ISO2557-2:1979 and which has been withdrawn. This standard differs from BS2782:Method 940B:1981 principally in the following respects. a) The term “reversion” is used in place of “shrinkage” throughout t
8、he document and related definitions have been included accordingly. b) The text is based upon publication of the method of test for reversion separately from ISO2557-1, specifically as ISO8328 (see “Cross-references” and “Additional information” in this national foreword). c) Moulding conditions are
9、 specified in part by requirements for the average injection velocity, with the introduction of an associated reference to ISO294 and hence BS2782:Method 910A. d) The term “bar” is used in place of “strip” for reference to the form of test specimen profile covered by ISO2557-1 and hence BS2782:Metho
10、d 940A. e) The title of the1986edition of ISO2557-2 differs from that of the1979 edition in the following respects: 1) the term “specified reversion” replaces “defined level of shrinkage”; 2) the terms “moulding material”, “rectangular” and “injection moulding” have been deleted. The title of BS2782
11、:Method 940B has been changed to adopt the term “specified reversion” but retains reference to the key feature of “injection moulding rectangular plates”, which distinguishes this method from that of BS2782:Method 940A. Terminology and conventions. The text of the International Standard has been app
12、roved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current
13、practice to use a full point on the baseline as the decimal marker. Wherever the words “part of ISO2557” and “International Standard” appear, referring to this standard, they should be read as “British Standard”. Cross-references International Standard Corresponding British Standard BS 2782 Methods
14、of testing plastics ISO 294:1975 Method 910A:1977 Injection moulding test specimens of thermoplastic materials (Identical) ISO 2557-1:1976 Method 940A:1981 Preparation of test specimens of amorphous thermoplastic moulding material with a defined level of shrinkage in the form of parallelepipedic bar
15、s by compression moulding and injection moulding (Identical)BS2782-9:Method940B:1989 BSI 12-1999 iii The related British Standard to ISO2818:1980 is BS2782:Method 930A:1977 “Preparation of test specimens by machining”, which is identical with the1974edition of ISO2818. A revision of ISO2818:1980 is
16、in preparation and is expected to be more acceptable as a basis for revision of BS2782:Method930A:1977. There is no British Standard corresponding to ISO/DIS8328 because the method of test to be provided thereby is incorporated in the1981 edition of BS2782:Method 940A, by alignment with the1976editi
17、on of ISO2557-1. Additional information. The following apply. a) Pending publication of ISO8328, for the purposes of 3.3 reference should be made to BS2782:Method 940A:1981 for details of the heat treatment applicable to obtain test specimens in their basic state. In thus making any reference to ISO
18、2557-1:1976, pending the publication of the revision referred to in clause 2 or pending the publication of ISO8328, allowances need to be made for use in BS2782:Method 940B:1989 of the term “reversion” in contexts where the term “shrinkage” was used in ISO2557-1:1976 and hence BS2782:Method 940A:198
19、1. b) Attention is drawn to the fact that many thermoplastics materials specifications, national and international, current at the date of publication of this standard use the term “shrinkage” for either: 1) moulding shrinkage, i.e. the difference in dimensions between a moulding and the mould cavit
20、y in which it was moulded, both the mould and the moulding being at normal room temperature when measured (term 3.5.17 of BS1755-1:1982); or 2) the percentage change in length when a (moulded) specimen is subjected to a (further) specified heat treatment. For item 2) the term “reversion” is used in
21、the1986 editions of DIS8328 and DIS2557-1, which were accepted by Technical Committee ISO/TC61 for publication, and hence also in this edition of BS2782:Method 940B. Hence unless and until such specifications adopt the term “reversion” in place of “shrinkage” where applicable, it may be necessary to
22、 appreciate those contexts where the use of these two terms remains synonymous. c) Attention is drawn to the introduction to BS2782:Method 940A (clause0) which also applies to this Method. The introduction states that “for industrial purposes, the conditions of similar state are reasonably fulfilled
23、 when the measured shrinkages of test specimens produced by a specified heat treatment are equal”. Subsequent to the publication of ISO2557-1, experimental evidence has shown that this might not always be the case. Mouldings of the same amorphous polymer giving similar shrinkage have shown significa
24、ntly different mechanical properties (e.g.tensile strength), and mouldings giving significantly different shrinkage have shown similar tensile strength. This apparently results especially from extreme changes in processing conditions and may be a consequence of different types or distributions of or
25、ientation within the specimen. These effects may be aggravated by unequal cooling, leading to different shrinkages on the two sides of the specimen (see7.1 of BS2782:Method 940B) which may result from using inserted plates to reduce the mould thickness (see6.2 of BS2782:Method940B).BS2782-9:Method94
26、0B:1989 iv BSI 12-1999 WARNING NOTE. This British Standard method, which is identical with ISO2557-2, 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 appropriate safety precautions and t
27、he method should be operated only 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 British Standard does not of itself confer immunity from lega
28、l obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesitoiv, pages1to6, 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 t
29、he inside front cover.BS2782-9:Method940B:1989 BSI 12-1999 1 1 Scope and field of application This part of ISO2557 specifies the procedure for the preparation of test specimens with predominantly monoaxial orientation in the form of rectangular plates, made from rigid amorphous thermoplastic materia
30、l. Cellular plastic materials and fibre-containing plastic materials are excluded. The rectangular plates may be used for impact testing by the falling weight method. Bars cut from the plate in different directions may serve as test specimens for the determination of the dependence of mechanical str
31、ength upon the degree and direction of the predominant orientation in the plate. 2 References ISO 294, Plastics Injection moulding test specimens of thermoplastic materials. ISO 2557-1, Plastics Amorphous thermoplastics Preparation of test specimens with a specified reversion Part 1: Bars 1) . ISO 2
32、818, Plastics Preparation of test specimens by machining. ISO 8328, Plastics Amorphous thermoplastics Determination of reversion 2) . 3 Definitions For the purpose of this International Standard, the following definitions apply. 3.1 state of a specimen the condition of a specimen as characterized by
33、 its longitudinal reversion 3.2 specified state of specimens the state in which the specimens have a specified level of reversion which is either specified in the relevant International Standard or established by agreement between the interested parties 3.3 basic state of specimens the state in whic
34、h the specimens are nearly free of internal stresses and orientation. The specimens shall be considered to be in their basic state if, after the heat treatment specified in ISO8328, the surface does not change; the values of their mechanical properties are unchanged; their maximum reversion is nearl
35、y zero. NOTEThe maximum reversion to be considered as nearly zero depends on the type of thermoplastic and should be specified in the relevant material standard. 3.4 reversion the percentage change in length of a defined portion of a moulded specimen when this specimen is subjected to a specified he
36、at treatment: where S is the reversion; L 0 is the length before heat treatment (initial length); L 1 is the length after the specified heat treatment (final length). 3.5 maximum reversion (S m ) the reversion measured when the specimen is subjected to a heat treatment at a temperature above the gla
37、ss transition temperature of the material, high enough to make the degree of reversion independent of small changes in heating time or temperature 3.6 partial reversion (S p ) the reversion measured under specified conditions of heat treatment that are less extreme than those used to produce maximum
38、 reversion. S p , in contrast to S m , is influenced by the temperature and the time of treatment (S p S m ) 4 Moulding conditions The injection moulding conditions for the rectangular plate shall be set in such a way that in the specimen a predominantly monoaxial orientation results parallel to the
39、 longitudinal axis of the mould. For this purpose, the mould shall consist of two parts, viz. the relaxation area and the cavity. The uncontrolled orientations of the melt due to flow through the nozzle of the moulding machine relax in the relaxation area. The relaxation area and the cavity are conn
40、ected by a film gate (seeFigure 1). The flow through the film gate determines the final orientation of the melt. The degree of orientation of the melt depends upon its temperature, viscosity, velocity of injection and other specific properties of the melt. The state of the specimen also depends on t
41、he subsequent cooling. 1) At present at the stage of draft. (Revision of ISO 2557-1:1976.) 2) At present at the stage of draft.BS2782-9:Method940B:1989 2 BSI 12-1999 The average injection velocity, calculated in accordance with ISO294, shall be within the range150to300mm/s. The selected average inje
42、ction velocity, the corresponding injection time and the mould temperature shall be kept constant for a given material. Any change in reversion of the specimen will then be due to a change in the plastic melt temperature. For comparison of samples of different materials of the same type, it is essen
43、tial that the average injection velocity shall be the same for all materials. The values of reversion of the specimens cut lengthwise or crosswise shall not differ by more than 2% absolute. In addition, the reversion of the specimen cut crosswise shall be zero or negative. Positive reversion of thes
44、e specimens indicates biaxial orientation due to incomplete relaxation in the relaxation area, for example by low plastic melt temperatures. Rectangular plates in the basic state can be prepared according to ISO2557-1, by thermal relaxation in a mould cavity with dimensions identical to those of the
45、 injection mould. The plate has attained its basic state if bars cut lengthwise and crosswise show the same mechanical properties. 5 Design and shape of the plate 5.1 An example of a test plate50mm 80mm with predominantly monoaxial orientation is shown inFigure 1. The injection moulded specimen is c
46、omposed of a triangular relaxation area which is connected by a film gate to the rectangular test plate. The thickness of the relaxation area increases from the vertex to the base. The moulding material is injected near the vertex either by a pin-point gate( . 1,1mm) or by a sprue ( . 4mm) correspon
47、ding to the thickness of the specimen. 5.2 To ensure a continuous filling of the mould, the film gate shall be situated flush with one surface of the plate over the complete length of the narrow side. The film gate shall be thick enough to avoid sink marks. In the example given inFigure 1, the thick
48、ness of the gate shall be1,0mm. 5.3 The surfaces of the plate have slightly different states of orientation and accordingly different mechanical properties due to the position of the film gate. The ejector pins of the mould shall be positioned on the opposite side from the film gate so that the mark
49、ings form these ejector pins will identify one side of the specimen. 6 Injection mould 6.1 The mould can be used with a normal sprue or with a hot-runner with a pin-point gate. It is recommended that only single-cavity moulds be used in order to facilitate production of identical specimens by exact reproduction of the moulding conditions. 6.2 Depending on the moulding material, it may be advantageous to reduce the thickness of the test specimen, for example to2mm, by inserting appropriate plates in the mould. 6.3 Ejector pins shall b
