ISO/DIS 2507:2025(en)

ISO/TC 138/SC 5

Secretariat: NEN

Date: 2024-12-29

Thermoplastics pipes and fittings - Vicat softening temperature:

General test method and test conditions for vinyl chloride - based (PVC-U, PVC-C, PVC-HI) and acrylonitrile - based (ABS, ASA) pipes and fittings

© ISO 2025

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Contents

Foreword iv

Introduction v

1 Scope 1

2 Normative references 1

3 Terms and definitions 1

3.1 Penetration 1

3.2 Load 2

3.3 Vicat softening temperature VST 2

4 Principle 2

5 Apparatus 2

5.1 Means of producing penetration 2

5.2 Indenter 2

5.3 Heating equipment 3

5.4 Weights 3

5.5 Temperature-measuring device 3

5.6 Penetration-measuring device 3

5.7 Micrometers and gauges 4

5.8 Oven with air circulation 4

6 Test specimens 5

6.1 Specimen preparation from pipes 5

6.2 Specimen preparation from fittings 7

6.3 Number of test specimen 7

7 Conditioning 7

7.1 General 7

7.2 Conditioning for specimens from acrylonitrile-based (ABS, ASA) pipes and fittings 7

8 Procedure 8

9 Test Report 8

Annex A 10

Annex B 10

Annex C 11

Annex D 11

Annex E 12

Bibliography Fout! Bladwijzer niet gedefinieerd.

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 of 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 www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the transport of fluids, Subcommittee SC 5, General properties of pipes, fittings and valves of plastic materials and their accessories – Test methods and basic specifications.

ISO 2507:1995 consists of the following parts, under the general title Thermoplastics pipes and fittings – Vicat softening temperature:

— Part 1: General test method

— Part 2: Test conditions for unplasticized poly(vinyl chloride) (PVC-U) or chlorinated poly(vinyl chloride) (PVC-C) pipes and fittings and for high impact resistant poly(vinyl chloride) (PVC-HI) pipes.

— Part 3: Test conditions for acrylonitrile/butadiene/styrene (ABS) and acrylonitrile/styrene/ acrylic ester (ASA) pipes and fittings.

This third edition cancels and replaces all three parts of the first edition (ISO 2507-1:1995; ISO 2507-2:1995; ISO 2507-3:1995), by merging all parts into one document (ISO 2507:2024) and has been technically revised.

The main changes are as follows:

— The document was modified following edition 6 of ISO 306:2022

— The procedure for test piece preparation from pipes and fittings is described more detailed

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

This International Standard is based on ISO 306.

For convenience of use, it has been considered preferable to draw up a complete document for use in determining the Vicat softening temperature of thermoplastics pipes and fittings. For further details, reference to ISO 306 is recommended.

Please note, however, that ISO 306 is applicable to materials in the form of sheets, whereas this International Standard is applicable to products in the form of pipes and fittings.

ISO 2507 gives the general conditions under which the Vicat softening temperature of pipes and fittings is determined and provides the particular requirements for conducting tests on pipes and fittings of various materials.

The basic specifications for various materials are given in the informative annexes.

Thermoplastics pipes and fittings - Vicat softening temperature: General test method and test conditions for vinyl chloride - based (PVC-U, PVC-C, PVC-HI) and acrylonitrile - based (ABS, ASA) pipes and fittings

ISO 2507 specifies a general method for determining the Vicat softening temperature (VST) of thermoplastics pipes and fittings. It includes the adaption of method B 50 of ISO 306: 2022 using a force of 50 N and a heating rate of 50 °C/h.

It includes the particular test conditions for determining the Vicat softening temperature (VST) of unplasticized poly(vinylchloride) (PVC-U) or chlorinated poly(vinylchloride) (PVC-C) pipes and fittings, for high impact resistance poly(vinylchloride) (PVC-HI) pipes and for acrylonitrile/butadiene/styrene (ABS) and acrylonitrile/styrene/acrylic ester (ASA) pipes and fittings.

It also gives, for information, the corresponding base specifications.

It is not applicable to crystalline or semi-crystalline polymers.

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 306:2022, Plastics — Thermoplastic materials — Determination of Vicat softening temperature (VST)

ISO 472, Plastics — Vocabulary

ISO 16012, Plastics — Determination of linear dimensions of test specimens

IEC 60584‑1, Thermocouples -Part 1: EMF specifications and tolerances

IEC 60584‑3, Thermocouples - Part 3: Extension and compensating cables - Tolerances and identification system

IEC 60751, Industrial platinum resistance thermometers and platinum temperature sensors

For the purposes of this document, the terms and definitions given in ISO 472 and the following apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at https://www.electropedia.org/

3.1

Penetration

distance over which the indenting tip has to penetrate into the specimen under test

Note 1 to entry: It is expressed in millimetres (mm).

3.2

Load

force applied to test specimen by means of the indenting tip

Note 1 to entry: It is expressed in Newtons (N).

3.3

Vicat softening temperature VST

temperature at which a flat-ended indenter will penetrate the specimen to a depth of 1 mm under a specified load (3.2) using a selected uniform rate of temperature rise.

Note 1 to entry: It is expressed in degrees Celsius (°C)

The temperature at which a standard indenting tip with a flat point, under a standardised load penetrates (1,00 ± 0,01) mm into the surface of a test specimen, cut from the wall of a plastics pipe or a fitting, is determined. The intending tip exerts a specified force of (50 ± 1) N perpendicular to the test specimen, while the specimen is heated at a uniform rate of (50 ± 5) °C / h.

The temperature, in degree Celsius (°C), of the specimen, measured as close as possible to the indented area at 1 mm penetration, is quoted as the VST.

The apparatus shall be constructed essentially as shown in (Figure 1). It consists of a rigid metal frame in which a rod moves freely in the vertical direction. One end of the rod is fitted with a weight-carrying plate and the other end is equipped with an indenting tip. The base of the frame is fitted with a support plate or other suitable load-application device.

It is recommended that the rod and frame(s) be constructed of low thermal expansion material. Unless vertical parts of the apparatus have the same coefficient of linear thermal expansion, the difference in change of length of these parts during the test introduces an error in the reading of the apparent penetration of the test specimen.

At the time of manufacture, or after repair or replacement of test frame, a blank test shall be made on each apparatus using a test specimen made of rigid material having a low coefficient of expansion and a thickness comparable to that of the specimen under test. The blank test shall cover the temperature ranges to be used in the actual determination, and a correction term shall be determined for each temperature. If the correction term is 0,02 mm or greater, its value and algebraic sign shall be recorded; and the term applied to each test result by adding it algebraically to the reading of the apparent penetration of the test specimen.

NOTE Invar and borosilicate glass have been found suitable as materials for the test specimen in the blank test.

It shall be made of hardened steel, at least 2 mm long, of circular cross-section and of area (1,000 ± 0,015) mm² (corresponding to an indenting tip diameter of (1,128 ± 0,008) mm) and fixed at the bottom of the rod. The indenter, when in contact with the specimen, shall be perpendicular to the rod. The tip shall be free from burrs or other imperfections.

The heating equipment shall be a heating bath containing a suitable liquid or a fluidized bed. For heat transfer media other than gas (air) the test specimen shall be immersed to a depth of at least 35 mm.

An efficient stirrer or means to fluidize the solid heat transfer medium shall be provided. If liquids are used for heat transfer, it shall be established that the liquid chosen is stable over the temperature range used and does not affect the material under test, for example causing it to swell or crack.

The method using a liquid heat transfer medium shall be considered a reference method in case of doubts or conflicts, if possible, in the temperature range under consideration.

The heating equipment shall be provided with a control unit so that the temperature is raised at a uniform rate of (50 ± 5) °C/h.

The heating rate shall be verified periodically either by checking the automatic temperature reading, or manually checking the temperature. The requirement for the heating rate shall be considered satisfied if, over every 6 min interval during the test, the temperature change is (5,0 ± 0,5) °C.

It is allowable for the first 10 min or up to 40 °C of the ramp to be outside of the prescribed tolerances as many instruments use a PID control for the heating, and it is normal for the controller to tune itself to the correct power and interval requirements to perform the required ramp rate.

NOTE A means of accelerating the cooling rate of the heating equipment has been found to be desirable.

Liquid paraffin, transformer oil, glycerol and silicone oils are suitable heat transfer liquids, but others are acceptable. For fluidized beds, aluminium oxide powder has been found suitable.

A set of weights shall be provided so that the total load applied to the test specimen is (50,0 ± 1,0) N.

Use a suitable temperature-measuring device of appropriate range and with a resolution of 0,1 °C (or readable to 0,1 °C) and an accuracy of ±1 °C. The temperature-measuring devices shall be calibrated at the depth of immersion particular to the apparatus in use and in a temperature range that comprises the Vicat softening temperatures to be measured. It is recommended that the heating bath is equipped with a separate temperature-measuring device at each test station if there are several. In this case, the temperature-sensing part of the instrument shall be located not farther than 12,5 mm from the point where the indenting tip contacts the specimen. The temperature sensing part of the instrument shall not touch the specimen or be in contact with any part of the frame.

NOTE Methods of calibration of the temperature-measuring devices include static calibration (at one or more constant temperatures) and dynamic calibration (using a constant heating-rate). Dynamic calibration is capable of measuring temperature lag of the build-in temperature measuring device but requires a reference temperature measuring device with suitable dynamic properties.

Thermocouples shall be in accordance with the requirements of IEC 60584-1 and IEC 60584-3. Resistance thermometers shall be in accordance with the requirements of IEC 60751.

Use a calibrated dial gauge, or any other indicating or recording device, including electrical displacement sensing apparatus, such as a linear variable displacement transduce (LVDT), to measure the penetration of the specimen at the point where the indenting tip contacts the specimen. The penetration-measuring device shall be readable to 0,01 mm.

When analogue dial gauges are used, the thrust of the dial gauge, which contributes to the thrust on the test specimen, shall be recorded. The force of the dial gauge spring is directed upwards and is subtracted from the load; in other types, this force acts downwards and is added to the load. Since the force exerted by the spring in certain dial gauges varies considerably over the stroke, this force is measured at the position where the indenting tip has penetrated 1 mm into the specimen. The combined downward thrust, determined during calibration of the apparatus, due to the rod, the indenting tip and the upward or downward force exerted by the dial gauge spring in the measurement range used during the test, shall not exceed 1 N.

These are used to measure the width and thickness of the test specimens. They shall be readable to 0,01 mm and conform to ISO 16012.

Required only in case of testing materials which needs pre-drying and the heating equipment according 5.3 is not applicable. Capable to maintain the temperature at the value specified for these materials.

Key

Figure 1 — Schematic view of the testing apparatus with a heating equipment filled with liquid or fluidized powder bed for determination of the VST

Pipe rings are prepared by cutting pipes perpendicular to their axis. Segments are taken out from these rings to produce the test specimens. The dimensions shall be at least 9,5 mm in length (pipe axis) and at least 9,5 mm in width. See Figure 2.

Figure 2 — Schematic view of preparing test specimens from pipes

For segments from pipes with a wall thickness between 2,4 and 6 mm, no further preparation/treatment is required; the segments shall be used directly as test specimen.

For segments from pipes with a wall thickness greater than 6 mm, the thickness shall be reduced to (5 ± 1) mm by machining from the outside surface with a suitable technique to obtain the test specimens. See Figure 3.

Figure 3 — Schematic view of preparing test specimens out of pipe ring segments with a wall thickness > 6 mm

For segments from pipes with a wall thickness less than 2,4 mm, the test specimen shall comprise of two ring segments superimposed to obtain an overall thickness of at least 2,4 mm. The lower segment, which will serve as a base, shall be flattened by heating it up to 140 °C and keep it for 15 minutes at this temperature, while a suitable metal plate is resting on it. The upper segment shall be used untreated. See Figure 4.

Figure 4 — Schematic view of preparing test specimens out of pipe segments with a wall thickness < 2,4 mm by superimposed ring segments

Any cylindrical part of a fitting (socket, spigot, etc.) of suitable size and smooth surface can be used for determination of VST according to this document. The specimen preparation shall follow exactly the procedure described for pipes, also the size of the specimens shall be the same as for the samples taken from pipe. Attention shall be drawn not to use zones which includes weld lines, moulded markings, or an injection point.

If the socket of a fitting is threaded, machine the threaded part until a smooth surface is obtained. For fittings without cylindrical parts or without smooth surfaces, the test specimen preparation has to be agreed between the interested parties.

At least two test specimens shall be used to test a sample. It is recommended to prepare additional specimens in case the difference between the individual results is too large.

Specimens for testing shall be conditioned for at least 16 h at the normal climate 23/50-2 according to ISO 291 or in accordance with the appropriate product specification.

Note The conditioning time can be reduced to 4 h, if appropriate, but in case of a dispute the 16 hours are valid.

If the VST of the material under investigation is not affected by moisture, controlling of the relative humidity shall be omitted.

The test specimens can be submitted to annealing prior to testing if required by the appropriate product standard.

Immediately before conditioning in accordance with 7.1, the specimens shall be pre-dried as follows:

— Place the test pieces for 2 h in the oven (see 5.8) controlled at (90 ± 2) °C;

— Then let them cool in air at (23 ± 2) °C and (50 ± 5) % relative humidity, for (15 ± 1 min.

8.1 Mount the test specimen horizontally under the indenting tip of the unloaded rod, perpendicular to the indenting tip. The indenting tip shall at no point be nearer than 3 mm to the edge of the test specimen.

8.2 Place the rod/frame assembly in the heating equipment. The temperature of the heating equipment shall be a maximum of 25 °C at the start of each test, unless previous tests have shown that, for the material under test, no error is caused by starting at another temperature and the starting temperature is at least 50 °C below the expected VST.

For specimens from acrylonitrile- based (ABS, ASA) pipes and fittings, use the oven with air circulation (see 5.8) instead of the heating equipment (see 5.3).

8.3 With the indenter still in position, add a sufficient weight to the support plate (or load the indenter in another suitable way), so that the total load on the test specimen will be (50,0 ± 1,0) N. After 5 min with the load applied, note the reading of the indentation-measuring device (see 5.6) or set the instrument to zero.

8.4 Increase the temperature at a uniform rate of (50 ± 5) °C/h. Stir the heating medium well during the test.

8.5 Record the temperature of the heating medium when the indenter has penetrated into the test specimen by (1,00 ± 0,01) mm from its starting position, as defined in 8.3, and record it as the VST of the test specimen with one decimal.

8.6 Express the VST of the sample under test as the arithmetic mean of the VSTs of the specimens tested, provided the range of the individual results is smaller than 2 °C. If this is not the case, repeat the test a second time using an additional set of at least two test specimens. The test series, in which the range of individual results is smaller than 2 °C, shall be used for determining the VST of the sample tested. If this condition cannot be achieved, a VST of the sample cannot be expressed.

Report the VST with one decimal.

The test report shall include the following information:

a) a reference to this document, ISO 2507:2024;

b) full identification of the sample (pipe or fitting) tested, including the relevant dimensions and, in case of a multilayer pipe, the layer construction;

c) The thickness and the layers of composite test specimens (i.e., specimens consisting of more than one layer) if these are used;

d) the method of preparation of the test specimens out of the sample; for fittings, report also the position, where the specimens were taken;

e) the type of heating equipment;

f) the type of heat transfer media being used;

g) the conditioning and annealing procedures used, if any;

h) the mean Vicat softening temperature (VST) of the sample and the individual results of the test specimens, in degrees Celsius. If a VST cannot be expressed (see clause 8.6), report “mean Vicat softening temperature (VST): no result “. In this case, all individual results shall be reported;

i) any unusual characteristics of the test specimen noted during the test or after removal from the apparatus;

j) all operational details not included in this document, and any occurrence which may have influenced the result;

k) the date of the test.

1. 
   (informative)
   
   Unplasticized poly(vinyl chloride) (PVC-U) pipes and fittings – Basic specification

When tested in accordance with ISO 2507, the Vicat softening temperature should be:

— not less than 79,0 °C for unplasticized poly (vinyl chloride) (PVC-U) pipes

— not less than 77,0 °C for unplasticized poly (vinyl chloride) (PVC-U) fittings

For specific applications which need more stringent requirements, minimum values greater than those specified above are given in the relevant product standard.

1. 
   (informative)
   
   Chlorinated poly(vinyl chloride) (PVC-C) pipes and fittings – Basic specification

When tested in accordance with ISO 2507, the Vicat softening temperature should be:

— not less than 90,0 °C for chlorinated poly (vinyl chloride) (PVC-C) non-pressure pipes

— not less than 110,0 °C for chlorinated poly (vinyl chloride) (PVC- C) pressure pipes

— not less than 103,0 °C for chlorinated poly (vinyl chloride) (PVC-C) fittings

For specific applications which need more stringent requirements, minimum values greater than those specified above are given in the relevant product standard.

1. 
   (informative)
   
   High impact resistant poly (vinyl chloride) (PVC-HI) pipes – Basic specification

When tested in accordance with ISO 2507, the Vicat softening temperature should be:

— not less than 76,0 °C for high impact resistant poly (vinyl chloride) (PVC-HI) pipes

For specific applications which need more stringent requirements, a minimum value greater than that specified above are given in the relevant product standards.

1. 
   (informative)
   
   Acrylonitrile/butadiene/styrene (ABS) pipes and fittings – Basic specification

When tested in accordance with this part of ISO 2507, the Vicat softening temperature should be:

— not less than 90,0 °C for acrylonitrile/butadiene/styrene (ABS) pipes and fittings

For specific applications which need more stringent requirements, minimum values greater than those specified above are given in the relevant product standard.

1. 
   (informative)
   
   Acrylonitrile/styrene/ acrylic ester (ASA) pipes and fittings – Basic specification

When tested in accordance with ISO 2507, the Vicat softening temperature should be:

— not less than 90,0 °C for acrylonitrile/styrene/acrylic ester (ASA) pipes and fittings

For specific applications, which need more stringent requirements, minimum values greater than those specified are given in the relevant product standard.