ISO 16152:2022

INTERNATIONAL ISO
STANDARD 16152
Second edition
2022-06
Plastics — Determination of xylene-
soluble matter in polypropylene
Plastiques — Détermination des matières présentes dans le
polypropylène solubles dans le xylène
Reference number
© ISO 2022
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Method 1 — Reference method .1
4.1 Principle . 1
4.2 Apparatus . 1
4.3 Reagents and materials . 2
4.4 Procedure . 3
4.4.1 Preparation of the xylene . 3
4.4.2 Determination of level of impurities in the xylene (solvent blank) . 3
4.4.3 Determination of percentage xylene-soluble matter in the polypropylene . 4
4.5 Calculations . 6
4.6 Precision and bias . 7
5 Method 2 — Automated instrumental method . 7
5.1 Principle . 7
5.2 Apparatus . 7
5.3 Reagents and materials . 8
5.4 Procedure . 9
5.4.1 Preparation of the solvent . 9
5.4.2 Preparation of the sample . 9
5.4.3 Calibration curve. 9
5.4.4 Testing . 9
5.5 Calculation . 10
5.6 Precision and bias . 11
6 Test report .11
Annex A (informative) Precision data for polypropylene obtained from an intercomparison
of xylene-soluble content testing .12
Bibliography .13
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 9,
Thermoplastic materials.
This second edition cancels and replaces the first edition (ISO 16152:2005), which has been technically
revised.
The main changes are as follows:
— the introduction has been updated;
— the mandatory normative references clause has been added and subsequent clauses have been
renumbered;
— the pipette with capacity of 200 ml has been deleted from the list of apparatus;
— the symbols S , S and S have been replaced with w , w and w , respectively (see 3.1 and 4.5);
s m c s m c
— an automated instrumental method has been added (see Clause 5);
— a new informative Annex A (Precision data for polypropylene obtained from an intercomparison of
xylene-soluble content testing) has been added.
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
With the development of analytical and testing instruments, a new technique of measuring xylene-
soluble matter in polypropylene by automatic instrument has been developed. Automation improves the
precision, removing human-factor variability, and enhances safety for the laboratory and the operator.
The soluble content represents the fraction of amorphous material and it is important as it has a major
influence on the properties of the polypropylene.
The method is used to quantify the soluble/amorphous fraction in polypropylene homopolymers as
well as copolymers and can be used with other polyolefin materials, such as homopolymer polyethylene
or polyethylene α-olefin copolymers.
v
INTERNATIONAL STANDARD ISO 16152:2022(E)
Plastics — Determination of xylene-soluble matter in
polypropylene
1 Scope
This document specifies two methods of determining the mass fraction of a polypropylene homopolymer
or copolymer which is amorphous, expressed as soluble in xylene at 25 °C.
— Method 1: Reference method;
— Method 2: Automated instrumental method.
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
3 Terms and definitions
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
xylene-soluble fraction
w
s
percentage, by mass, of the polymer that does not precipitate out when a solution of the polymer in
xylene is cooled from reflux temperature to 25 °C and held at that temperature for a specified period of
time
4 Method 1 — Reference method
4.1 Principle
The polypropylene is dissolved in xylene under reflux conditions, then cooled under controlled
conditions and maintained at 25 °C, to ensure the complete crystallization of the insoluble fraction. The
xylene-soluble fraction is then recovered by evaporation of the xylene and determined by weighing the
residue.
4.2 Apparatus
4.2.1 Reflux condenser, length 400 mm.
4.2.2 Flat-bottomed flask, capacity 500 ml, with one or two necks, or conical flask or cylindrical
bottle of similar capacity.
4.2.3 Insulation disc, made of fiberglass or mineral wool.
4.2.4 Magnetic stirrer, with temperature-controlled hotplate, thermostatted oil bath or heating
block capable of maintaining 140 °C to 150 °C.
4.2.5 Stirrer bar.
4.2.6 Pipette, class A, 100 ml or equivalent.
4.2.7 Glass-stoppered flask, 250 ml.
4.2.8 Thermostatically controlled water bath, with sufficient cooling capacity to maintain a
constant bath temperature of 25 °C ± 0,5 °C while cooling down the flask containing the xylene/polymer
solution (see 4.4.3.8 and 4.4.3.9).
4.2.9 Filter paper, fluted, at least 125 mm in diameter.
4.2.10 Funnel, 60°or equivalent, at least 125 mm in diameter.
4.2.11 Vacuum oven.
4.2.12 Disposable aluminium pans, 300 ml capacity, with smooth sides.
4.2.13 Temperature-controlled hotplate.
4.2.14 Analytical balance, with a minimum weighing sensitivity of 0,1 mg (a sensitivity of 0,01 mg is
preferred).
4.2.15 Desiccator, containing an appropriate desiccant.
4.2.16 Timer, preferably with an alarm, reading in minutes.
4.2.17 Oven, conventional forced-air or gravity-convection type.
4.3 Reagents and materials
4.3.1 Reagent-grade ortho-xylene(o-xylene), assay by gas chromatography (GC) 98 % min.;
ethylbenzene content as determined by GC less than 2 %; evaporation residue at 140 °C less than
0,002 g/100 ml; boiling point 144 °C.
4.3.2 Reagent-grade para-xylene(p-xylene), assay by gas chromatography (GC) 98 % min.;
ethylbenzene content as determined by GC less than 2 %; evaporation residue at 140 °C less than
0,002 g/100 ml; boiling point 138 °C.
Reagent-grade ortho-xylene (4.3.1) shall be used as the reference solvent whenever there is dispute
between laboratories on test results, unless the laboratories agree otherwise.
4.3.3 Antioxidants, 2,6-Di-tert-butyl-4-methylphenol (BHT), or Pentaerythritol tetrakis(3-(3,5-di-
tert-butyl-4-hydroxyphenyl)propionate)(1010).
4.4 Procedure
4.4.1 Preparation of the xylene
4.4.1.1 Although stabilization of the xylene is not required, antioxidants shall be added to prevent
degradation when testing un
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