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1、 Reference number ISO 20965:2005(E) ISO 2005 INTERNATIONAL 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 Copyright International Organ
2、ization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 21:54:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 20965:2005(E) PDF disclaimer This PDF file may contain embedded typeface
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5、d for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. ISO 2005 All rights reserved. Unless otherwise specified, no par
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7、6 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2005 All rights reserved Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/997254
8、5001 Not for Resale, 04/18/2007 21:54:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 20965:2005(E) ISO 2005 All rights reserved iii Contents Page Forewordiv 1 Scope1 2 Normative references .1 3 Terms and definitions.1 4 General principles.3 5 Apparatus.3 6 Sampling
9、and specimen preparation6 7 Procedure.7 8 Analysis of extensional flow measurements .8 9 Precision11 10 Test report11 Annex A (informative) Checking for swelling of specimens due to immersion in silicone oil or other fluids.12 Annex B (informative) Uncertainties in transient extensional viscosity te
10、sting13 Bibliography .18 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 21:54:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 20965:2005(E) iv I
11、SO 2005 All rights reserved Foreword ISO (the International Organization for Standardization) 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 intereste
12、d in a subject for which a technical committee has been established has the right 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 Com
13、mission (IEC) on all matters of electrotechnical standardization. International 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 techni
14、cal committees are circulated to the member bodies for voting. Publication as 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 sh
15、all not be held responsible for identifying any or all such patent rights. ISO 20965 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical- chemical properties. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NAS
16、A Technical Standards 1/9972545001 Not for Resale, 04/18/2007 21:54:53 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD ISO 20965:2005(E) ISO 2005 All rights reserved 1 Plastics Determination of the transient extensional viscosity of polymer melts 1 Sc
17、ope This International 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. T
18、he method is capable of measuring the transient extensional viscosity of polymer melts at Hencky strain rates typically in the range 0,01 s1 to 1 s1, 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 exte
19、nsional viscosity values typically in the range from approximately 104 Pas to 107 Pas (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 ins
20、trument, in terms 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
21、 is given in the 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) appl
22、ies. ISO 472, Plastics 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 Whorlow 1 for strains and strain rates, and by the Nomenclature Committee of the Society of
23、 Rheology for start-up flow in tensile uniaxial extension at constant Hencky strain rate 2. 3.1 Hencky strain strain given by the natural logarithm of the elongation ratio = ln(l/l0) (1) where l is the specimen length and l0 is the original specimen length Copyright International Organization for St
24、andardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 21:54:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 20965:2005(E) 2 ISO 2005 All rights reserved NOTE 1 It is also referred to as the natu
25、ral 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 l0. NOTE 2 It is expressed in reciprocal seconds. 3.3 net tensile stress E for tensile uni
26、axial extension, stress given by E = 11 22 = 11 33 = zz rr (3) where ii is 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 tensile stress is expressed in pascals. 3.4 te
27、nsile 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 Standard as “transient extensional viscos
28、ity”. NOTE 2 It is a transient term. NOTE 3 It is expressed in pascal seconds. 3.5 tensile viscosity E term given by EE ( , )( , )lim t tt + =? (5) NOTE 1 It is the limiting tensile stress growth coefficient value and represents an equilibrium extensional viscosity if a steady value is achieved. How
29、ever, 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. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA
30、 Technical Standards 1/9972545001 Not for Resale, 04/18/2007 21:54:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 20965:2005(E) ISO 2005 All rights reserved 3 4 General principles In contrast to shear flow where reference is normally made only to steady shear flow b
31、ehaviour, 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 stress growth behaviour in which the stress continually increases with increasing strain until the
32、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 extensional viscosity is thus dependent on strain rate but not on strain or time. Normally, the exten
33、sional 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 Hencky strain of an element of fluid within a flow is independent of its original length and is determin
34、ed 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 can be used to generate quantitatively accurate data on the extensional viscoelasticity of polymer m
35、elts. 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 International Standard describes the first of these: constant strain rate. In this method, the strain rate i
36、s 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 of the force and deformation of the specimen, the stresses and strains and hence strain rate can be d
37、etermined. 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. The notation used in these figures is defined in 8.1. Type A: Two rotating clamps. Each clamp shall c
38、onsist 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 likely that the force will be easier to measure, and will be measured with greater accuracy, on a f
39、ixed 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. Figure 1 Schematic diagram of type A test instrument Copyright International Organization for Standard
40、ization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 21:54:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 20965:2005(E) 4 ISO 2005 All rights reserved Type B: A single rotating clamp and a fixed cla
41、mp. The rotating clamp shall consist of either a single rotating element or a pair of rotating elements. The force exerted on the specimen 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 dia
42、gram of type C test instrument Type D: Single translating (non-rotating) clamp. Figure 4 Schematic diagram of type D test instrument In each of these configurations, the specimen is mounted between the clamps and is stretched uniaxially. The requirements for the apparatus are that it shall permit th
43、e measurement or determination of the force acting on the specimen, and the strain and strain rate of the specimen subjected to a constant 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
44、clamps, or be measured directly from the dimensions and/or local velocities of the specimen. 5.2 Silicon bath/temperature-controlled chamber 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 he
45、ating using forced gas, a gas may be used in the chamber surrounding the test specimen to provide the required test environment, for example nitrogen to provide an inert atmosphere. NOTE 2 The use of a silicone oil bath may permit more rapid heating of the specimen. Copyright International Organizat
46、ion for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/18/2007 21:54:53 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 20965:2005(E) ISO 2005 All rights reserved 5 For low-viscosity materials, it
47、 is essential to support the specimen during heat-up and testing (to avoid it 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
48、 are matched at the test temperature. If a forced-gas oven is used, then support 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 also Note 1 in 7.1). When quantitative results