ISO 18177:2025

International
Standard
ISO 18177
First edition
Plastics — Test method for
2025-05
estimation of the short chain
branching distribution of
semicrystalline ethylene 1-olefin
copolymers — Differential scanning
calorimetry (DSC)
Plastiques — Méthode d'essai pour l'estimation de la
distribution des ramifications à chaînes courtes des copolymères
d'éthylène-1-oléfines semi-cristallins — Analyse calorimétrique
différentielle (DSC)
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus and materials . 2
6 Test specimens . 2
7 Test conditions and specimen conditioning . 3
8 Calibration . 3
9 Procedure . 3
9.1 Setting up the apparatus .3
9.2 Loading the test specimen into the crucible .3
9.3 Insertion of crucibles .3
9.4 Determination of the minimum temperature within self-nucleation domain of the
specimen .3
9.5 Temperature scan .4
10 Expression of results . 6
10.1 Determination of multiple melting peaks temperatures and peak area of each melting
peak .6
10.2 Calculation of short chain branching .7
10.3 Calculation of degree of crystallinity .8
10.4 Calculation of short chain branching ratio .9
10.5 Format for expression of results .9
11 Test report . 10
Annex A (normative) Self-nucleation experiment.12
Annex B (informative) Interlaboratory precision study .16
Bibliography .20

iii
Foreword
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iv
Introduction
The short chain branching distribution (SCBD) of polyethylene is a fundamental structural parameter, which,
together with the molecular weight distribution, determines the properties of polyethylene materials. It is
emphasized that with the same type and amount of 1-olefin comonomer, the physical-mechanical behaviour
of the polyethylene can be significantly changed by adjusting the SCBD, and then affects the properties of final
products. Therefore, it is very important to obtain information about the SCBD to characterize polyethylene
in detail. Separation techniques are successfully applied for quantitative determination of the SCBD of
[1]
polyethylene, which require specific instrumentation, being sometimes laborious or time consuming.
However, these solvent separation techniques cannot distinguish intra-molecule heterogeneity. The thermal
fractionation technique of successive self-nucleation and annealing (SSA) can be used to distinguish the
polymer chains with different branching degrees from the same molecule or different molecules and was
[2]
first reported by Muller et al. in 1997 using conventional DSC. Using high performance DSC combined with
reduced sample mass scan rates up to 200 K/min can be achieved maintaining good peak resolution. This
[3]
enabled reduction of SSA fractionation times from several hours to approximately 30 min. More recent
developments in chip calorimetry enabled much higher scan rates in the order of thousands of K/s and allow
observation of polymer crystallisation at a much shorter time scale with similar resolution compared to
conventional DSC. This technique does not only offer a significant reduction of required time but enables
[4]
also additional information on very early stages and molecular mechanisms of thermal fractionation.
The final differential scanning calorimetry (DSC) heating run of the polymer after SSA treatment shows
a series of melting peaks. The multiple melting peaks are derived from the melting of crystallites with
different mean lamellar thicknesses, which presumably correspond to the chain segments with different
[5],[6]
crystallizable sequences or degrees of branching. Under the premise of ignoring the co-crystallization
[7],[8],[9],[10]
of the melt at self-nucleation temperature, the degree of branching and crystallinity of each
[5],[11]
fraction as a function of melting temperature are determined from empirically-derived equations.
Therefore, the amount of chain segments with different branching degrees can be characterized according
to the integral area of multiple melting peaks after considering the degree of crystallinity, and the SCBD can
[5],[11],[15]
be obtained. SSA establishes a method for the estimation of the chemical composition distribution
excluding amorphous highly branched components that do not crystallize up to the minimum crystallization
temperature selected for experiments. The main advantages of the SSA thermal fractionation method are
simple, fast, eco-friendly and cost-less.

v
International Standard ISO 18177:2025(en)
Plastics — Test method for estimation of the short chain
branching distribution of semicrystalline ethylene 1-olefin
copolymers — Differential scanning calorimetry (DSC)
1 Scope
This document specifies a test method for the estimation of the short chain branching distribution of
semicrystalline ethylene 1-olefin copolymers by successive self-nucleation and annealing (SSA) with
conventional, high performance and fast differential scanning calorimetry.
This document is applicable to the estimation of the short chain branching distribution of raw materials of
semicrystalline ethylene 1-olefin copolymers and its products.
Quantitative calculation of short chain branching content, degree of crystallinity and short chain branching
distribution is applicable to ethylene/1-butene copolymers, ethylene/1-hexene copolymers and ethylene/1-
octene copolymers.
2 Normative references
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 472, Plastics — Vocabulary
ISO 11357-1, Plastics — Differential scanning calorimetry (DSC) — Part 1: General principles
ISO 23976, Plastics — Fast differential scanning calorimetry (FSC) — Chip calorimetry
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472, ISO 11357-1, ISO 23976 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
short chain branching
oligomeric offshoot branching from the backbone chain of a polymer
3.2
degree of branching
F
number of short chain branches per 1 000 backbone carbon atoms
...