ISO 18373-1:2007

INTERNATIONAL ISO
STANDARD 18373-1
First edition
2007-07-15
Rigid PVC pipes — Differential scanning
calorimetry (DSC) method —
Part 1:
Measurement of the processing
temperature
Tubes rigides en PVC — Méthode utilisant la calorimétrie différentielle à
balayage —
Partie 1: Mesurage de la température de procédé

Reference number
©
ISO 2007
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ii ISO 2007 – All rights reserved

Foreword
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(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
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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 18373-1 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 18373 consists of the following parts, under the general title Rigid PVC pipes — Differential scanning
calorimetry (DSC) method:
— Part 1: Measurement of the processing temperature
— Part 2: Measurement of the enthalpy of fusion of crystallites
©
ISO 2007 – All rights reserved iii

Introduction
Studies have been undertaken at the international level to determine a method of measuring the B-onset or
maximum processing temperature used during the production of rigid PVC pipes. These studies have
demonstrated that a test using differential scanning calorimetry (DSC) fulfils these requirements.
The method involves taking small samples from the pipe wall and heating these in a differential scanning
calorimeter. Small endotherms are used to detect the thermal history of the samples and the B-onset or
maximum processing temperature is derived from these data.
The technique requires a good understanding of DSC instruments and techniques, particularly in relation to
PVC. It is important that newcomers to the technique familiarize themselves with both the instrumentation and
method prior to undertaking reportable tests.
It is intended that individual product standards will specify the requirements for B-onset or maximum processing
temperature.
The method can also be suitable for other types of extruded rigid PVC products, but different sampling protocols
might be required.
©
iv ISO 2007 – All rights reserved

INTERNATIONAL STANDARD ISO 18373-1:2007(E)
Rigid PVC pipes — Differential scanning calorimetry (DSC)
method —
Part 1:
Measurement of the processing temperature
1Scope
This part of ISO 18373 specifies a method for the determination of the processing temperature of rigid PVC
pipe samples. The method is based on the measurement of the thermal history using differential scanning
calorimetry (DSC) and is suitable for all types of rigid PVC pipes.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
baseline tilting
adjustment of the angle of the baseline to bring it to the horizontal
2.2
curve magnification
magnification of the differential scanning calorimetry (DSC) curve around A-onset and B-onset temperature
(“zooming”)
2.3
A-onset
indication of first crystallite melting
2.4
B-onset
indication of maximum processing temperature (T )
p
2.5
instrumental baseline
measurement with empty sample pan, i.e. background subtraction
2.6
position of sample
location in the product from where the sample was taken
2.7
purge gas
gas used to ensure an inert environment
2.8
repeat samples
samples from the same position
©
ISO 2007 – All rights reserved 1

3Principle
DSC is a well-established method for testing the melt temperature in PVC products (see References [1]
and [2]).
The benefits with this test are that an accurate assessment can be made of the processing temperature, as well
as the possibility of finding variations in the processing temperature in local areas of the product, due to the fact
that only a small size of sample is required for the test. This enables the operator to cut samples from different
locations around the pipe circumference. Thus, temperature variations in the pipe wall can be examined.
The characteristic B-onset temperature occurs because crystallites with melting points at or above the
maximum processing temperature (T ) will be annealed, thus slightly raising their melting point. Crystallites that
p
do melt at T will recrystallize on cooling and therefore will have melting points below T . Thus, there are very
p p
few crystallites with melting temperatures in the immediate vicinity of T .
p
4 Apparatus
4.1 DSC instrument, and associated software, calibrated.
Calibration should be carried out using at least two different metals. An instrumental baseline must be obtained
with an empty sample pan and reference pan in place, and with temperature settings and purge gas identical to
the settings to be used for the sample analysis.
4.2 Aluminium sample pans.
4.3 Inert purge gas (e.g. N , Ar, etc.), of at least industrial quality.
4.4 Analytical balance, with an accuracy to within 0,01 mg.
4.5 Slow-speed saw (see Reference [3]), knife, or any other device introducing neither heat nor stress into
the sample as it is cut.
5 Preparation of the test pieces and the test
◦ ◦ ◦ ◦
5.1 Take at least
...