1、BRITISH STANDARD BS ISO 20965:2005 Plastics Determination of the transient extensional viscosity of polymer melts ICS 83.080.01 BS ISO 20965:2005 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 12 April 2005 BSI 12 April 2005 ISBN 0 580 45779
2、 6 National foreword This British Standard reproduces verbatim ISO 20965:2005 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee PRI/21, Testing of plastics, which has the responsibility to: A list of organizations represented
3、on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “
4、Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from lega
5、l obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Su
6、mmary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to iv, pages 1 to 18, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication
7、Amd. No. Date Comments Reference number ISO 20965:2005(E) OSI 5002INTERNATIONAL STANDARD ISO 20965 First edition 2005-02-15 Plastics Determination of the transient extensional viscosity of polymer melts Plastiques Dtermination de la viscosit longationelle transitoire des polymres ltat fondu BSISO209
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13、s ersedevr iiiContents Page Foreword iv 1 Scope 1 2 Normative references. 1 3 Terms and definitions. 1 4 General principles. 3 5 Apparatus. 3 6 Sampling and specimen preparation 6 7 Procedure. 7 8 Analysis of extensional flow measurements .8 9 Precision 11 10 Test report 11 Annex A (informative) Che
14、cking for swelling of specimens due to immersion in silicone oil or other fluids. 12 Annex B (informative) Uncertainties in transient extensional viscosity testing 13 Bibliography . 18 BSISO20965:2005IS:56902 O5002(E) iv I SO 5002 All irthgs ersedevrForeword ISO (the International Organization for S
15、tandardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the ri
16、ght to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Internationa
17、l Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as
18、an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO
19、 20965 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical- chemical properties. BSISO20965:2005INTENRATIONAL TSANDADR IS:56902 O5002(E)I SO 5002 All irthgs ersedevr 1Plastics Determination of the transient extensional viscosity of polymer melts 1 Scope This Internat
20、ional Standard specifies the general principles of a method for determining the transient extensional viscosity of polymer melts. The procedure details the measurement of polymer melt specimens stretched uniaxially under conditions of constant strain rate and constant temperature. The method is capa
21、ble of measuring the transient extensional viscosity of polymer melts at Hencky strain rates typically in the range 0,01 s 1to 1 s 1 , at Hencky strains up to approximately 4 and at temperatures up to approximately 250 C (see Notes 1 and 2). It is suitable for measuring transient extensional viscosi
22、ty values typically in the range from approximately 10 4Pas to 10 7Pas (see Note 3). NOTE 1 Hencky strains and strain rates are used (see Clause 3). NOTE 2 Values of strain, strain rate and temperature outside these limiting values may be attained. NOTE 3 The operating limit of an instrument, in ter
23、ms of the lowest transient extensional viscosity values that can be measured, is due to a combination of factors, including the ability of the specimen to maintain its shape during testing and the resolution of the instrument. A list of documents related to this International Standard is given in th
24、e Bibliography. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 472, P
25、lastics Vocabulary 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 472, together with the following, apply. Definitions 3.1 to 3.5 are given by Whorlow1for strains and strain rates, and by the Nomenclature Committee of the Society of Rheology for sta
26、rt-up flow in tensile uniaxial extension at constant Hencky strain rate2 . 3.1 Hencky strain strain given by the natural logarithm of the elongation ratio = ln(l/l 0 ) (1) where l is the specimen length and l 0is the original specimen length BSISO20965:2005IS:56902 O5002(E) 2 I SO 5002 All irthgs er
27、sedevrNOTE 1 It is also referred to as the natural or true strain. NOTE 2 It is dimensionless. 3.2 Hencky strain rate rate of change of Hencky strain with time, given by 1/ / llt = (2) where t is time NOTE 1 It is independent of the original specimen length l 0 . NOTE 2 It is expressed in reciprocal
28、 seconds. 3.3 net tensile stress Efor tensile uniaxial extension, stress given by E= 11 22= 11 33= zz rr(3) where iiis a stress tensor in either rectangular or axisymmetric co-ordinates NOTE 1 The tensile stress growth function is indicated by E +where the +indicates start-up of flow. NOTE 2 Net ten
29、sile stress is expressed in pascals. 3.4 tensile stress growth coefficient E +ratio of the net tensile stress to the Hencky strain rate EE (, ) / t + = (4) for tensile uniaxial extension, where t is time and +indicates start-up of flow NOTE 1 It is also known for the purposes of this International S
30、tandard as “transient extensional viscosity”. NOTE 2 It is a transient term. NOTE 3 It is expressed in pascal seconds. 3.5 tensile viscosity Eterm given by EE (, ) (, ) lim t tt + = (5) NOTE 1 It is the limiting tensile stress growth coefficient value and represents an equilibrium extensional viscos
31、ity if a steady value is achieved. However, for materials that do not exhibit a steady-state behaviour, the use of an “equilibrium extensional viscosity” such as this is not appropriate. NOTE 2 It is expressed in pascal seconds. BSISO20965:2005IS:56902 O5002(E) I SO 5002 All irthgs ersedevr 34 Gener
32、al principles In contrast to shear flow where reference is normally made only to steady shear flow behaviour, extensional flow behaviour is best described as being transient. In describing the transient behaviour of materials in extension at constant strain rate, they may exhibit either an unbounded
33、 stress growth behaviour in which the stress continually increases with increasing strain until the material fails, or the stress reaches a steady value with increasing strain thus yielding a tensile or equilibrium extensional viscosity. The latter occurs typically at large strains. An equilibrium e
34、xtensional viscosity is thus dependent on strain rate but not on strain or time. Normally, the extensional viscosity will vary as a function of both strain and strain rate as well as temperature. In describing and modelling plastics processing, the use of Hencky strain is preferred. The rate of Henc
35、ky strain of an element of fluid within a flow is independent of its original length and is determined only from the velocity field of that element. It is thus a more suitable characteristic of the flow. Strain and strain rate are taken by default herein to be Hencky values. Stretching flow methods
36、can be used to generate quantitatively accurate data on the extensional viscoelasticity of polymer melts. In carrying out extensional flow measurements, there are four types of measurement that are normally made: constant strain rate, constant stress, constant force and constant speed. This Internat
37、ional Standard describes the first of these: constant strain rate. In this method, the strain rate is uniform throughout the specimen and is held constant with time. The basic principle behind stretching flow measurements is to subject a specimen to a tensile stretching deformation. By measurement o
38、f the force and deformation of the specimen, the stresses and strains and hence strain rate can be determined. 5 Apparatus 5.1 General description The measuring apparatus shall consist of one of the following types, shown in Figures 1 to 4. These types define the various instrument configurations. T
39、he notation used in these figures is defined in 8.1. Type A: Two rotating clamps. Each clamp shall consist of either a single rotating element or a pair of rotating elements only the pair arrangement is shown. The force exerted on the specimen can be measured at the fixed or rotating end. NOTE It is
40、 likely that the force will be easier to measure, and will be measured with greater accuracy, on a fixed clamp rather than on a moving clamp as there will be fewer complications due, for example, to vibration and the inertia of the clamp which may introduce noise and errors into the force signal. Fi
41、gure 1 Schematic diagram of type A test instrument BSISO20965:2005IS:56902 O5002(E) 4 I SO 5002 All irthgs ersedevrType B: A single rotating clamp and a fixed clamp. The rotating clamp shall consist of either a single rotating element or a pair of rotating elements. The force exerted on the specimen
42、 is normally measured at the fixed end. Figure 2 Schematic diagram of type B test instrument Type C: Two translating (non-rotating) clamps. Figure 3 Schematic diagram of type C test instrument Type D: Single translating (non-rotating) clamp. Figure 4 Schematic diagram of type D test instrument In ea
43、ch of these configurations, the specimen is mounted between the clamps and is stretched uniaxially. The requirements for the apparatus are that it shall permit the measurement or determination of the force acting on the specimen, and the strain and strain rate of the specimen subjected to a constant
44、 strain rate under isothermal conditions. The strain and strain rate of the specimen shall either be derived from the displacements and/or speeds of the clamp or clamps, or be measured directly from the dimensions and/or local velocities of the specimen. 5.2 Silicon bath/temperature-controlled chamb
45、er Heating may be provided by placing the specimen in a silicone oil bath or in a temperature-controlled chamber with a forced gas flow through it. NOTE 1 When heating using forced gas, a gas may be used in the chamber surrounding the test specimen to provide the required test environment, for examp
46、le nitrogen to provide an inert atmosphere. NOTE 2 The use of a silicone oil bath may permit more rapid heating of the specimen. BSISO20965:2005IS:56902 O5002(E) I SO 5002 All irthgs ersedevr 5For low-viscosity materials, it is essential to support the specimen during heat-up and testing (to avoid i
47、t sagging under the influence of gravity). NOTE 3 The use of a silicone oil bath results in the specimen being supported by the silicone oil due to its buoyancy, particularly if the densities of the silicone oil and specimen are matched at the test temperature. If a forced-gas oven is used, then sup
48、port of the specimen can be obtained by the cushioning effect provided by the gas. Silicone oil may be absorbed by some polymers. A check should preferably be made to see if the immersion time affects the measured properties of the polymer by varying the length of the immersion time (see Annex A and
49、 also Note 1 in 7.1). When quantitative results are required, then this check shall be made. NOTE 4 Even if the silicone oil does not affect the shape of the tensile stress growth coefficient versus strain (or time) plot, it may affect the point of failure of the specimen. Thus assessment of the effect of the silicone oil on the measured properties should consi
