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`
`INTERNATIONAL
`STANDARD
`
`ISO
`899-1
`Third edition
`2017-09
`
`Part 1:
`
`Plastics — Determination of creep
`behaviour —
`
`Tensile creep
`Plastiques — Détermination du comportement au fluage —
`Partie 1: Fluage en traction
`
`Please share your feedback about
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`Reference number
`ISO 899-1:2017(E)
`© ISO 2017
`
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`ISO 899-1:2017(E)
`
`
`COPYRIGHT PROTECTED DOCUMENT
`
`© ISO 2017, Published in Switzerland
`All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
`or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
`written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
`the requester.
`ISO copyright office
`Ch. de Blandonnet 8 • CP 401
`CH-1214 Vernier, Geneva, Switzerland
`Tel. +41 22 749 01 11
`Fax +41 22 749 09 47
`copyright@iso.org
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`
`ii
`
`
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`ISO 899-1:2017(E)
`
`
`Contents
`
`1
`2
`3
`4
`5
`6
`
`Page
`Foreword ........................................................................................................................................................................................................................................iv
`Scope .................................................................................................................................................................................................................................1
`Normative references ......................................................................................................................................................................................1
`Terms and definitions .....................................................................................................................................................................................1
`Apparatus .....................................................................................................................................................................................................................3
`Test specimens........................................................................................................................................................................................................4
`Procedure.....................................................................................................................................................................................................................4
`6.1
`Conditioning and test atmosphere ........................................................................................................................................4
`6.2 Measurement of test-specimen dimensions ..................................................................................................................5
`6.3 Mounting the test specimens ......................................................................................................................................................5
`6.4
`Selection of stress value ..................................................................................................................................................................5
`6.5
`Loading procedure ...............................................................................................................................................................................5
`6.5.1
`Preloading ..............................................................................................................................................................................5
`6.5.2
`Loading .....................................................................................................................................................................................5
`6.6
`Extension-measurement schedule .........................................................................................................................................5
`6.7
`Time measurement .............................................................................................................................................................................5
`6.8
`Temperature and humidity control .......................................................................................................................................6
`6.9 Measurement of recovery rate (optional) .......................................................................................................................6
`Expression of results ........................................................................................................................................................................................6
`7.1 Method of calculation ........................................................................................................................................................................6
`7.1.1
`Tensile-creep modulus, Et .......................................................................................................................................6
`7.1.2 Nominal tensile-creep modulus, E*t ..............................................................................................................6
`7.2
`Presentation of results .....................................................................................................................................................................7
`7.2.1
`Creep curves ........................................................................................................................................................................7
`7.2.2
`Creep-modulus/time curves ..................................................................................................................................7
`7.2.3
`Isochronous stress-strain curves .......................................................................................................................8
`7.2.4
`Three-dimensional representation ..................................................................................................................8
`7.2.5
`Creep-to-rupture curves............................................................................................................................................8
`Precision .......................................................................................................................................................................................................9
`7.3
`Test report ...................................................................................................................................................................................................................9
`Annex A (informative) Physical-ageing effects on the creep of polymers ...................................................................10
`Bibliography .............................................................................................................................................................................................................................14
`
`7
`
`8
`
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`
`
`
`iii
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`ISO 899-1:2017(E)
`
`
`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 interested 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 Commission (IEC) on all matters of
`electrotechnical standardization.
`The procedures used to develop this document and those intended for its further maintenance are
`described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
`different types of ISO documents should be noted. This document was drafted in accordance with the
`editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
`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. Details of
`any patent rights identified during the development of the document will be in the Introduction and/or
`on the ISO list of patent declarations received (see www.iso.org/patents).
`Any trade name used in this document is information given for the convenience of users and does not
`constitute an endorsement.
`For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
`expressions related to conformity assessment, as well as information about ISO's adherence to the
`World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
`URL: www.iso.org/iso/foreword.html
`This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 2,
`Mechanical behaviour.
`This third edition cancels and replaces the second edition (ISO 899-1:2003), of which it constitutes a
`minor revision to update the normative references in Clause 2. It also incorporates the Amendment
`ISO 899-1:2003/Amd.1:2015.
`A list of all parts in the ISO 899 series can be found on the ISO website.
`
`iv
`
`
`
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`INTERNATIONAL STANDARD
`
`ISO 899-1:2017(E)
`
`Tensile creep
`
`1 Scope
`
`2 Normative references
`
`Plastics — Determination of creep behaviour —
`
`Part 1:
`This document specifies a method for determining the tensile creep of plastics in the form of standard
`test specimens under specified conditions such as those of pretreatment, temperature and humidity.
`The method is suitable for use with rigid and semi-rigid non-reinforced, filled and fibre-reinforced
`plastics materials in the form of dumb-bell-shaped test specimens moulded directly or machined from
`sheets or moulded articles.
`The method is intended to provide data for engineering-design and research and development purposes.
`Data for engineering-design purposes requires the use of extensometers to measure the gauge length
`of the specimen. Data for research or quality-control purposes may use the change in distance between
`the grips (nominal extension).
`Tensile creep can vary significantly with differences in specimen preparation and dimensions and in
`the test environment. The thermal history of the test specimen can also have profound effects on its
`creep behaviour (see Annex A). Consequently, when precise comparative results are required, these
`factors are intended to be carefully controlled.
`If tensile-creep properties are used for engineering-design purposes, the plastics materials are intended
`to be tested over a broad range of stresses, times and environmental conditions.
`The following documents are referred to in the text in such a way that some or all of their content
`constitutes requirements 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 291, Plastics — Standard atmospheres for conditioning and testing
`ISO 472, Plastics — Vocabulary
`ISO 527-1:2012, Plastics — Determination of tensile properties — Part 1: General principles
`ISO 527-2, Plastics  —  Determination  of  tensile  properties  —  Part  2:  Test  conditions  for  moulding  and 
`For the purposes of this document, the terms and definitions given in ISO 472 and the following apply.
`ISO and IEC maintain terminological databases for use in standardization at the following addresses:
`— IEC Electropedia: available at http://www.electropedia.org/
`— ISO Online browsing platform: available at http://www.iso.org/obp
`© ISO 2017 – All rights reserved
`
`extrusion plastics
`
`3 Terms and definitions
`
`
`
`1
`
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`
`
`3.1
`creep
`
`3.2
`initial stress
`
`F A
`
`σ =
`
`F
`
`A
`
`3.3
`extension
`
`increase in strain with time when a constant force is applied
`σtensile force per unit area of the initial cross-section within the gauge length
`Note 1 to entry: It is given by the formula
`where
`
`is the force, in newtons;
`
`is the average initial cross-sectional area within the narrow (gauge) section of the specimen, in square
`millimetres.
`Note 2 to entry: It is expressed in megapascals.
`(ΔL)t
`increase in the distance between the gauge marks, expressed in millimetres, at time t
`Note 1 to entry: It is given by the formula
`where
`
`is the gauge length, in millimetres, at any given time t during the test;
`
`is the original gauge length, in millimetres, of the specimen after application of a preload but prior to
`L0
`application of the test load.
`(ΔL*)t
`increase in the distance between the grips (increase in grip separation)
`Note 1 to entry: It is given by the formula
`where
`
`L*t
`is the distance between the grips at any given time t during the test, in millimetres;
`
`L*0 is the initial distance between the grips, expressed in millimetres, holding the specimen after application
`of a preload but prior to application of the test load.
`
`)∆L
`
`(
`
`t
`
`L
`t=
`
`L
`− 0
`
`Lt
`
`3.4
`nominal extension
`
`∗
`)∆L
`
`(
`
`t
`
`=
`
`∗
`L
`t
`
`−
`
`∗
`L
`0
`
`2
`
`
`
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`ISO 899-1:2017(E)
`
`
`3.5
`tensile-creep strain
`
`εt
`
`=
`
`(
`
`tL
`)∆
`L
`
`0
`
`3.6
`nominal tensile-creep strain
`
`εtchange in the distance between the gauge marks, relative to the initial distance, produced by the applied
`load at any given time t during a creep test
`Note 1 to entry: It is given by the formula
`Note 2 to entry: It is expressed as a dimensionless ratio or as a percentage.
`ε*tchange in the distance between the grips, relative to the initial distance, produced by the applied load
`at any given time t during a creep test
`Note 1 to entry: It is given by the formula
`Note 2 to entry: It is expressed as a dimensionless ratio or as a percentage.
`Etratio of initial stress to tensile-creep strain
`E*tratio of initial stress to nominal tensile-creep strain
`Cartesian plot of stress versus creep strain, at a specific time after application of the test load
`period of time the specimen is under full load until rupture
`initial stress which will just cause rupture (σ B,t) or will produce a specified strain (σε,t) at a specified
`time t, at a given temperature and relative humidity
`decrease in strain at any given time after completely unloading the specimen, expressed as a percentage
`of the strain just prior to the removal of the load
`4.1 Gripping device, capable of ensuring that the direction of the load applied to the test specimen
`coincides as closely as possible with the longitudinal axis of the specimen. This ensures that the test
`© ISO 2017 – All rights reserved
`
`ε∗
`=t
`
`(
`
`∗
`tL
`)∆
`∗
`L
`
`0
`
`3.7
`tensile-creep modulus
`
`3.8
`nominal tensile-creep modulus
`
`3.9
`isochronous stress-strain curve
`
`3.10
`time to rupture
`
`3.11
`creep-strength limit
`
`3.12
`recovery from creep
`
`4 Apparatus
`
`
`
`3
`
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`ISO 899-1:2017(E)
`
`
`specimen is subjected to simple stress and that the stresses in the loaded section of the specimen may be
`assumed to be uniformly distributed over cross-sections perpendicular to the direction of the applied load.
`It is recommended that grips be used that will allow the specimen to be fixed in place, correctly aligned,
`prior to applying the load. Self-locking grips which allow the specimen to move as the load increases are
`not suitable for this test.
`4.2 Loading system, capable of ensuring that the load is applied smoothly, without causing transient
`overloading, and that the load is maintained to within ± 1 % of the desired load. In creep-to-rupture tests,
`provision shall be made to prevent any shocks which occur at the moment of rupture being transmitted
`to adjacent loading systems. The loading mechanism shall allow rapid, smooth and reproducible loading.
`4.3 Extension-measuring device, comprising any contactless or contact device capable of measuring
`the extension of the specimen gauge length or the increase in the distance between the clamp grips under
`load without influencing the specimen behaviour by mechanical effects (e.g. undesirable deformations,
`notches), other physical effects (e.g. heating of the specimen) or chemical effects.
`In the case of contactless (optical) measurement of the strain, the longitudinal axis of the specimen
`shall be perpendicular to the optical axis of the measuring device. To determine the increase in length
`of the test specimen, an extensometer shall be used which records the increase in the distance between
`the clamp grips. The accuracy of the extension-measuring device shall be better than ± 0,01 mm.
`For creep-to-rupture tests, it is recommended that the extension be measured by means of a contactless
`optical system operating on the cathetometer principle. Automatic indication of time to rupture is
`highly desirable. The gauge length shall be marked on the specimen, either by attaching (metal) clips
`with scratched-on gauge marks, or by ruling the gauge marks with an inert, thermally stable paint.
`Electrical-resistance strain gauges are suitable only if the material tested is of such a nature as to
`permit such strain gauges to be attached to the specimen by means of adhesive and only if the adhesion
`quality is constant during the duration of the test. The modulus of the strain gauge when bonded to the
`specimen shall be such that the specimen is not reinforced.
`4.4 Time-measurement device, accurate to 0,1 %.
`4.5 Micrometer, reading to 0,01 mm or closer, for measuring the initial thickness and width of the test
`specimen.
`Use test specimens of the same shape and dimensions as specified for the determination of tensile
`properties by the relevant material standard or, by default, as specified in ISO 527-2.
`Condition the test specimens as specified in the International Standard for the material under test. In
`the absence of any information on conditioning, use the most appropriate set of conditions specified in
`ISO 291, unless otherwise agreed by the interested parties.
`The creep behaviour will be affected not only by the thermal history of the specimen under test, but
`also by the temperature and (where applicable) humidity used in conditioning (see ISO 10350-1). If the
`specimen is not in humidity equilibrium, creep will be affected in the following way: a specimen which
`is too dry will produce an additional strain due to water absorption during the test and a specimen
`which is too humid will contract due to water desorption. It is recommended that a conditioning time
`≥ t90 (see ISO 62) be used.
`© ISO 2017 – All rights reserved
`
`6.1 Conditioning and test atmosphere
`
`5 Test specimens
`
`6 Procedure
`
`4
`
`
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`
`
`6.3 Mounting the test specimens
`
`6.4 Selection of stress value
`
`6.5 Loading procedure
`
`6.5.1 Preloading
`
`6.5.2 Loading
`
`6.2 Measurement of test-specimen dimensions
`
`Conduct the test in the same atmosphere as used for conditioning, unless otherwise agreed upon by
`the interested parties, e.g. for testing at elevated or low temperatures. Ensure that the variation in
`temperature during the duration of the test remains within ± 2 °C.
`Measure the dimensions of the conditioned test specimens in accordance with ISO 527-1:2012, 9.2.
`Mount a conditioned and measured specimen in the grips and set up the extension-measuring device as
`required.
`Select a stress value appropriate to the application envisaged for the material under test, and calculate,
`using the formula given in 3.2, the load to be applied to the test specimen.
`If the initial strain is specified instead of the stress, the stress value may be calculated using tensile
`modulus for the material (see ISO 527-1).
`When it is necessary to preload the test specimen prior to increasing the load to the test load, for
`example in order to eliminate backlash by the test gear, take care to ensure that the preload does not
`influence the test results. Do not apply the preload until the temperature and humidity of the test
`specimen (gripped in the test apparatus) correspond to the test conditions. Measure the gauge length
`after application of the preload. Maintain the preload during the whole duration of the test.
`Load the test specimen smoothly so that full loading of the specimen is reached between 1 s and 5 s
`after the beginning of the application of the load. Use the same rate of loading for each of a series of
`tests on one material.
`Take the total load (including the preload) to be the test load.
`Record the point in time at which the specimen is fully loaded as t = 0. Unless the extension is
`automatically and/or continuously recorded, choose the times for making individual measurements as
`a function of the creep curve obtained from the particular material under test. It is preferable to use the
`following measurement schedule:
`1 min, 3 min, 6 min, 12 min and 30 min;
`1 h, 2 h, 5 h, 10 h, 20 h, 50 h, 100 h, 200 h, 500 h, 1 000 h, etc.
`If discontinuities are suspected or observed in the creep-strain versus time plot, take readings more
`frequently.
`Measure, to within ± 0,1 % or ± 2 s (whichever is the less severe tolerance), the total time which has
`elapsed up to each creep measurement.
`© ISO 2017 – All rights reserved
`
`6.6 Extension-measurement schedule
`
`6.7 Time measurement
`
`
`
`5
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`
`6.8 Temperature and humidity control
`
`6.9 Measurement of recovery rate (optional)
`
`7 Expression of results
`
`7.1 Method of calculation
`
`Unless temperature and relative humidity (where applicable) are recorded automatically, record them
`at the beginning of the test and then at least three times a day initially. When it has become evident that
`the conditions are stable within the specified limits, they may be checked less frequently (but at least
`once a day).
`Upon completion of non-rupture tests, remove the load rapidly and smoothly and measure the recovery
`rate using, for instance, the same schedule as was used for creep measurement.
`7.1.1 Tensile-creep modulus, Et
`Calculate the tensile-creep modulus, Et, by dividing the initial stress, σ, by the tensile-creep strain, εt, at
`each of the selected measurement times.
`It is given, in megapascals, by Formula (1):
`
`(1)
`where
`
`is the applied force, in newtons;
`is the initial gauge length, in millimetres;
`
`L0
`
`is the initial cross-sectional area, in square millimetres, of the specimen;
`
`is the extension, in millimetres, at time t.
`(ΔL)t
`7.1.2 Nominal tensile-creep modulus, E*t
`Calculate the nominal tensile-creep modulus, E*t, by dividing the initial stress, σ, by the nominal tensile-
`creep strain, ε*t, at each of the selected measurement times.
`It is given, in megapascals, by Formula (2):
`
`(2)
`where
`
`is the applied force, in newtons;
`is the initial distance between the grips, in millimetres;
`
`L*0
`
`is the initial cross-sectional area of the specimen, in square millimetres;
`
`is the increase in the distance between the grips, in millimetres, at time t.
`(ΔL*)t
`© ISO 2017 – All rights reserved
`
`
`
`L
`F
`⋅
`
`
`O
`L
`A
`⋅ ∆ )
` (
`
`t
`
` =
`
`σε
`
`t
`
`E
`
`t
`
`=
`
`F
`
`A
`
`*
`
`E
`
`=
`
`t
`
`σ
`ε
`*
`
`t
`
` =
`
`L
`F
`⋅
`*
`
`
`L
`A
`⋅ ∆
` (
`
`
`O
`*)
`t
`
`F
`
`A
`
`6
`
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`
`
`7.2 Presentation of results
`
`7.2.1 Creep curves
`
`If testing is carried out at different temperatures, the raw data should preferably be presented, for each
`temperature, as a series of creep curves showing the tensile strain plotted against the logarithm of
`time, one curve being plotted for each initial stress used (see Figure 1).
`
`Key
`t
`εt
`
`log10 time
`creep strain
`1
`increasing stress
`The data may also be presented in other ways, e.g. as described in 7.2.2 and 7.2.3, to provide information
`required for particular applications.
`For each initial stress used, the tensile-creep modulus, calculated in accordance with 7.1.1, may be
`plotted against the logarithm of the time under load (see Figure 2).
`
`Figure 1 — Creep curves
`
`7.2.2 Creep-modulus/time curves
`
`Key
`t
`Et
`
`log10 time
`creep modulus
`1
`increasing stress
`© ISO 2017 – All rights reserved
`
`Figure 2 — Creep-modulus/time curves
`
`
`
`7
`
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`
`
`7.2.3
`
`Isochronous stress-strain curves
`
`If testing is carried out at different temperatures, plot a series of curves for each temperature.
`An isochronous stress-strain curve is a Cartesian plot showing how the strain depends on the applied
`load, at a specific point in time after application of the load. Several curves are normally plotted,
`corresponding to times under load of 1 h, 10 h, 100 h, 1 000 h and 10 000 h. Since each creep test gives
`only one point on each curve, it is necessary to carry out the test at, at least, three different stresses,
`and preferably more, to obtain an isochronous curve (see ISO 11403-1).
`To obtain an isochronous stress-strain curve for a particular time under load (say 10 h) from a series
`of creep curves as shown in Figure 1, read off, from each creep curve, the strain at 10 h, and plot these
`strain values (x-axis) against the corresponding stress values (y-axis). Repeat the process for other
`times to obtain a series of isochronous curves (see Figure 3).
`
`Key
`εt
`σ
`
`Figure 3 — Isochronous stress-strain curves
`
`creep strain
`stress
`1
`increasing time
`If testing is carried out at different temperatures, plot a series of curves for each temperature.
`A relationship of the form ε = f (t,σ) exists between the different types of curve (see Figures 1 to 3) that
`can be derived from the raw creep-test data. This relationship can be represented as a surface in a
`three-dimensional space (see Reference [4]).
`All the curves that can be derived from the raw creep-test data form part of this surface. Because
`of the experimental error inherent in each measurement, the points corresponding to the actual
`measurements normally do not lie on the curves but just off them.
`The surface ε = f (t,σ) can therefore be generated by deriving a number of the curves which form it, but a
`number of sophisticated smoothing operations are usually necessary. Computer techniques permit this
`to be done rapidly and reliably.
`Creep-to-rupture curves allow the prediction of the time to failure at any stress. They may be plotted as
`stress against log time to break (see Figure 4) or log stress against log time to break.
`© ISO 2017 – All rights reserved
`
`7.2.4 Three-dimensional representation
`
`7.2.5 Creep-to-rupture curves
`
`8
`
`
`
`ClearCorrect Exhibit 1066, Page 12 of 20
`
`

`

`Licensed to Finnegan, Henderson, Farabow, Garrett & Dunner LLP / Aaron Sterngass (aaron.sterngass@finnegan.com)
`ISO Store Order: OP-877739 license #1/ Downloaded: 2025-02-25
`Single user licence only, copying and networking prohibited.
`
`ISO 899-1:2017(E)
`
`
`Key
`t
`σ
`
`Figure 4 — Creep-to-rupture curves
`
`log10 time to break
`stress
`1
`increasing temperature
`NOTE
`The stress, σ, may also be plotted on a logarithmic scale.
`The precision of this test method is not known because interlaboratory data are not available. When
`interlaboratory data are obtained, a precision statement will be added at the following revision.
`The test report shall include the following particulars:
`a) a reference to this document;
`b) a complete description of the material tested, including all pertinent information on composition,
`preparation, manufacturer, tradename, code number, date of manufacture, type of moulding and
`any annealing;
`c)
`the dimensions of each test specimen;
`d) the method of preparation of the test specimens;
`e)
`the directions of the principal axes of the test specimens with respect to the dimensions of the
`product or some known or inferred orientation in the material;
`f) details of the atmosphere used for conditioning and testing;
`g) which tensile creep modulus, Et or E*t, was calculated;
`h)
`the creep-test data for each temperature at which testing was carried out, presented in one or more
`of the graphical forms described in 7.2, or in tabular form;
`i)
`if recovery-rate measurements are made, the time-dependent strain after unloading the test
`specimen (see 6.9).
`
`7.3 Precision
`
`8 Test report
`
`© ISO 2017 – All rights reserved
`
`
`
`9
`
`ClearCorrect Exhibit 1066, Page 13 of 20
`
`

`

`Licensed to Finnegan, Henderson, Farabow, Garrett & Dunner LLP / Aaron Sterngass (aaron.sterngass@finnegan.com)
`ISO Store Order: OP-877739 license #1/ Downloaded: 2025-02-25
`Single user licence only, copying and networking prohibited.
`
`ISO 899-1:2017(E)
`
`
`Annex A
`
`(informative)
`
`
`Physical-ageing effects on the creep of polymers
`
`A.1 General
`
`Physical ageing takes place when a polymer is cooled from an elevated temperature at which the
`molecular mobility is high to a lower temperature at which relaxation times for molecular motions are
`long in comparison with the storage time at that temperature. Under these circumstances, changes
`in the structure will take place over a long period of time, involving rearrangement in the shape
`and packing of molecules as the polymer approaches the equilibrium structural state for the lower
`temperature. Associated with this ageing process, there is a progressive decrease in the molecular
`mobility of the polymer, even when the temperature remains constant. As a direct con