ISO 18177:2025

Plastics - Test method for estimation of the short chain branching distribution of semicrystalline ethylene 1-olefin copolymers - Differential scanning calorimetry (DSC)

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.

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)

General Information

• Status: Published
• Publication Date: 12-May-2025
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: ISO/TC 61/SC 9 - Thermoplastic materials
• Drafting Committee: ISO/TC 61/SC 9 - Thermoplastic materials
• Current Stage: 6060 - International Standard published
• Start Date: 13-May-2025
• Due Date: 13-Sep-2025
• Completion Date: 13-May-2025

Overview

ISO 18177:2025 - Plastics: Test method for estimation of the short chain branching distribution of semicrystalline ethylene 1‑olefin copolymers - Differential scanning calorimetry (DSC) describes a standardized DSC procedure using successive self‑nucleation and annealing (SSA) to estimate the short chain branching distribution (SCBD) of semicrystalline ethylene/1‑olefin copolymers. It covers use with conventional, high‑performance and fast (chip) differential scanning calorimetry (DSC/FSC) and applies to both raw materials and finished products. Quantitative calculations for short chain branching content, degree of crystallinity and branching distribution are explicitly applicable to ethylene/1‑butene, ethylene/1‑hexene and ethylene/1‑octene copolymers.

Key topics and technical requirements

• Technique: Successive self‑nucleation and annealing (SSA) combined with DSC thermal fractionation to produce multiple melting peaks representing fractions with different branching.
• Measured outputs: Melting temperatures, melting enthalpies, degree of crystallinity (χc), short chain branching content (F) and short chain branching ratio (DF).
• Instrument classes: Procedures and specimen handling are specified for conventional DSC, high‑performance DSC (higher scan rates, lower sample mass) and fast DSC / chip calorimetry (very high scan rates).
• Specimen mass guidance:
  • Conventional DSC: typically 2–10 mg (2–3 mg common)
  • High‑performance DSC: can use ≈0.5 mg or lower
  • Fast DSC (chip): on the order of 100 ng to 1 µg
• Calibration and conditioning: Follow ISO 11357‑1 (conventional and high‑performance DSC) and ISO 23976 (fast DSC) for calibration, specimen preparation and test conditions.
• Limitations: Method characterizes the crystallizable portion; highly branched, non‑crystallizing fractions may be excluded from the SCBD estimate.
• Data processing: Empirically derived equations link melting peak areas/temperatures to branching degree and crystallinity; results expressed as distributions of branching vs. melting temperature.

Practical applications

• Polymer characterization and quality control for polyethylene copolymers (ethylene/1‑butene, /1‑hexene, /1‑octene).
• R&D and process development to correlate short chain branching distribution with mechanical and rheological properties.
• Supplier qualification, batch comparison and troubleshooting in compounding, extrusion and film/blow molding production.
• Faster thermal fractionation using high‑performance or fast DSC reduces analysis time (SSA fractionation reduced from hours to minutes with advanced DSC and chip calorimetry), enabling higher throughput in labs.

Who should use this standard

• Polymer analysts, DSC laboratory managers, R&D teams, quality control engineers and material scientists working with semicrystalline ethylene 1‑olefin copolymers.
• Instrument manufacturers and calibration labs implementing SSA protocols on conventional, high‑performance or fast DSC platforms.

Related standards

• ISO 11357‑1 - Plastics - Differential scanning calorimetry (DSC): general principles
• ISO 23976 - Plastics - Fast differential scanning calorimetry (FSC) - Chip calorimetry
• ISO 472 - Plastics - Vocabulary

Keywords: ISO 18177, DSC, SSA, short chain branching distribution, semicrystalline ethylene 1‑olefin copolymers, degree of crystallinity, fast DSC, thermal fractionation.

Standards Content (Sample)

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
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
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or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
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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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 9, Thermoplastic
materials.
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.

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

3.3
short chain branching ratio
D
F
mass fraction of chain segments with different degrees of oligomeric offshoot branches belonging to relative
thermal fractionation melting peaks
3.4
self-nucleation
SN
nucleation process triggered by self-seeds or self-nuclei that are generated in a given polymeric material by
a specific thermal protocol
3.5
successive self-nucleation and annealing
SSA
thermal fractionation process performed on DSC using a temperature program consisting of a combination
of specifically designed subsequent heating and cooling cycles and holding times
3.6
self-nucleation temperature
T
S
isothermal temperature set in the SSA program that allows the sample to self-nucleate or/and crystallize
Note 1 to entry: T is the minimum temperature within the self-nucleation domain resulting in the maximum number
S1
of self-nuclei.
3.7
degree of crystallinity
χ
c
portion of three-dimensional order at the level of molecular dimensions in the polymer
Note 1 to entry: The degree of crystallinity is expressed in percent, %.
4 Principle
The successive self-nucleation and annealing steps are applied to the specimen by DSC to induce the formation
of nuclei and the growth of crystallites with different lamellar thicknesses presumably corresponding to
the chain segments of polymers with different degrees of branching. The melting temperatures and the
melting enthalpies of crystallites are determined from the curve thus obtained. The degree of branching and
crystallinity as a function of melting temperature are determined from empirically derived equations. The
ratio of the segment mass with the same degree of branching to the total segment mass gives an indication
of the short chain branching ratio D . The method is limited to the crystallizable part of the material.
F
NOTE The highly branched part of the sample is possibly disregarded in this document due to its small
crystallization peak area.
5 Apparatus and materials
The apparatus and materials shall be in accordance with ISO 11357-1 for conventional DSC.
High performance DSC is also based on ISO 11357, but due to higher sensitivity and enhanced noise filtering
techniques lower sample mass should be used and improved peak resolution is achieved.
The apparatus and materials for fast DSC shall be in accordance with ISO 23976.
6 Test specimens
The test specimen may be in the form of a powder, pellets or granules, or may be cut from sample pieces.
The test specimen shall be representative of the sample being examined and shall be prepared and handled

with care. If the specimen is taken from sample pieces by cutting, care shall be taken to prevent polymer
reorientation or any other effect that can alter the properties. If the specimen is taken from thick-wall
products, the internal and external surfaces of the products shall be avoided during specimen preparation.
The method of sampling and test specimen preparation shall be stated in the test report. If the specimen
crucible is closed or sealed with a lid, this shall not cause any deformation of the bottom of the crucible. Good
thermal contact between the specimen and crucible and between the crucible and holder shall be ensured.
For conventional DSC as specified in ISO 11357-1, typical specimen masses are between 2 mg and 10 mg, and
2 mg to 3 mg is most commonly used. For high performance DSC instruments that can run up to 750 K/min,
sample masses may be reduced to 0,5 mg or lower.
For fast DSC as specified in ISO 23976, the specimen masses shall be in the order of magnitude of 100 ng and
shall not exceed 1 µg. To avoid high temperature gradients, the samples shall be kept as thin as possible. The
lateral dimensions shall not exceed the active area of the chip sensor.
7 Test conditions and specimen conditioning
The test conditions and specimen conditioning are specified in ISO 11357-1 for conventional DSC and in
ISO 23976 for fast DSC. Test conditions and specimen conditioning for high performance DSC are also based
on ISO 11357-1, but higher scan rates and lower specimen mass should be used.
8 Calibration
The calibration procedures are specified in ISO 11357-1 for conventional and high-performance DSC and in
ISO 23976 for fast DSC.
9 Procedure
9.1 Setting up the apparatus
The procedure for setting up the apparatus is specified in ISO 11357-1 for conventional and high-performance
DSC, and in ISO 23976 for fast DSC.
9.2 Loading the test specimen into the crucible
For conventional and high-performance DSC, the procedure for loading the test specimen into the crucible is
specified in ISO 11357-1.
In fast DSC, an open specimen geometry is used, i.e. the specimen is directly placed in the centre of the active
area of the chip sensor. Further details of loading the test specimen onto the chip sensor are specified in
ISO 23976.
9.3 Insertion of crucibles
The procedure for inserting the crucibles using conventional and high-performance DSC is specified in
ISO 11357-1.
For fast DSC, no crucibles are used.
9.4 Determination of the minimum temperature within self-nucleation domain of the
specimen
The minimum temperature of the specimen within self-nucleation domain, T , shall be determined from the
S1
results of preceding self-nucleation experiments following the procedure outlined in Annex A.

9.5 Temperature scan
9.5.1 For conventional DSC, the heating and cooling rate, β , is commonly set to 10 K/min or 20 K/min.
If using high performance DSC, scan rates may be set up to several hundred K/min. Upon using higher
heating and cooling rates in high performance DSC instruments, sample masses may be reduced to obtain a
similar resolution of individual peaks in the final heating scan after SSA treatment.
For fast DSC, heating and cooling rates may be increased up to several thousand K/s resulting in similar
peak resolution in the final heating scan after SSA treatment.
The maximum usable cooling rate for high performance DSC and fast DSC depends on the performance of
the cooling device and the thermal conductivity of the purge gas. Best results are obtained using a liquid
nitrogen cooling accessory in combination with helium purge gas.
Preferably, the SSA parameters given in Table 1 should be used. Heating and cooling rates or holding times
other than those recommended here may be used by agreement between the interested parties.
Table 1 — Typical self-nucleation and annealing parameters for different DSC techniques
Conventional DSC High performance DSC Fast DSC
Hold time at T , t 3 min 3 min 0,1 s
max max
10 K/min or 100 K/min or
Initial cooling rate from T to T , β 100 K/s
max min i
20 K/min 200 K/min
Initial hold time at T , t 5 min 1 min 0,1 s
min min,i
10 K/min or 100 K/min or
Heating / cooling rate of SSA ramps, β 100 K/s
20 K/min 200 K/min
Hold time at T , t 20 min 1 min 1 ms to 10 s
Si TSi
Hold time at T during SSA ramps,
min
5 min 1 min 0,1 s
t
min,SSA
Final heating rate, β 5 K/min 200 K/min 100 K/s
f
9.5.2 Allow 5 min for nitrogen pre-purge prior to beginning the heating cycle.
9.5.3 Perform a first temperature scan heating the specimen to a maximum melting temperature, T ,
max
and hold at the temperature for the time, t , selected from Table 1 for the applicable DSC technique to
max
erase the test materials previous thermal history (see Figure 1). The maximum melting temperature shall
be 30 °C above the extrapolated end melting temperature, T , of the sample or higher if required by the
ef,m
polymer to be measured.
9.5.4 Cool down to a minimum temperature, T . The initial cooling rate, β , for this step and the initial
min i
holding time, t , at T shall be selected from Table 1 for the applicable DSC technique. The minimum
min,i min
temperature shall be 50 °C below the extrapolated end crystallization temperature, T according to
ef,c
ISO 11357-1, or lower if required by the polymer to be measured.
9.5.5 Heat up to the minimum temperature of the specimen within self-nucleation domain, T , at a scan
S1
rate, β , selected from Table 1 for the applicable DSC technique. The determination of T is given in Annex A.
1 S1
9.5.6 Equilibrate the test specimen at T for a time, t , selected from Table 1 for the applicable DSC
S1 TSi
technique.
For conventional DSC, there is no significant shift of SSA peaks between 5 min and 30 min holding time.
-3
For fast DSC, SSA melting peaks can be observed after 10 s holding time already. Increasing peak height
and slight temperature shift can be observed with increasing time. At 10 s holding time the quality of
fractionation is comparable to conventional DSC. This shift of peak heights and temperatures is a result of the
kinetic nature of the SN process. The melting curves after SSA treatment are lower by approximately 5 °C to

10 °C due to crystallization occurring at much lower temperatures because of the much higher cooling rates
from the melt. This should be considered specially when comparing samples with different DSC techniques.
9.5.7 Cool down to the minimum temperature established in 9.5.4 using a cooling rate, β , and hold at the
temperature for a time, t . Both the cooling rate to be used for SSA ramps and the holding time shall be
min,SSA
selected from Table 1 for the applicable DSC technique.
9.5.8 Heat up to the next T = (T -ΔT) °C (i=2,.), T ≥65 °C using a heating rate, β , selected from
Si S(i-1) Si 1
Table 1 for the applicable DSC technique. ΔT is usually selected among 2 K, 3 K, 4 K, 5 K and 6 K, and 5 K is
most commonly set. ΔT shall be kept constant throughout the SSA experiment.
NOTE The temperature interval ΔT is important to the resolution of thermal fractionation. Too narrow ΔT can
lead
...