CEN/TS 17627:2021

SLOVENSKI STANDARD
01-julij-2021
Polimerni materiali - Reciklirani polimerni materiali - Ugotavljanje deleža trdnih
onesnaževal
Plastics - Recycled plastics - Determination of solid contaminants content
Kunststoffe - Rezyklate - Bestimmung des Gehaltes an Feststoffverunreinigungen
Plastiques - Plastiques recyclés - Détermination de la teneur en contaminants solides
Ta slovenski standard je istoveten z: CEN/TS 17627:2021
ICS:
83.080.20 Plastomeri Thermoplastic materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TS 17627
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
May 2021
TECHNISCHE SPEZIFIKATION
ICS 83.080.20
English Version
Plastics - Recycled plastics - Determination of solid
contaminants content
Plastiques - Plastiques recyclés - Détermination de la Kunststoffe - Rezyklate - Bestimmung des Gehaltes an
teneur en contaminants solides Feststoffverunreinigungen
This Technical Specification (CEN/TS) was approved by CEN on 1 March 2021 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 17627:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 5
5 Apparatus and consumables . 5
5.1 Extruder . 5
5.2 Press . 6
5.3 Microscope . 6
5.4 Pointed metal rod . 6
5.5 Screen pack . 6
5.6 Plastic foil . 6
5.7 Purging material . 6
6 Sample preparation . 7
7 Procedure . 7
7.1 Extrusion . 7
7.2 Flattening . 7
7.3 Visual examination . 8
8 Evaluation . 8
8.1 Amount of solid contaminants . 8
8.2 Largest contaminant size (optional) . 8
8.3 Identification of the types (substance) of contaminants (optional) . 8
9 Report . 10
Annex A (informative) Apparatus illustrations . 11
Annex B (informative) Contaminant substance identification help . 12
Bibliography . 17

European foreword
This document (CEN/TS 17627:2021) has been prepared by Technical Committee CEN/TC 249
“Plastics”, the secretariat of which is held by NBN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Introduction
The use of recycled materials in production of plastics products is widely accepted nowadays
throughout the industry. Those recycled materials are mostly prepared from post-industrial or post-
consumer sources, which always contain more or less contamination by foreign bodies. Most of this
contamination is removed during the recycling process, either by washing and/or by melt filtration.
However, this removal is never perfect, leaving some small amounts of foreign bodies in the material
pellets.
For many applications that use recycled materials this little residue of contaminants is not posing any
problem. But for other, more demanding or more sensitive products (e.g. having thin wall sections) the
use of a recycled material is not an option, unless the number and size of those solid contaminants could
accurately be determined and controlled.
While some recyclers do have the means to determine and report a limited number of properties of
their material, like density, MFI etc., none of them is able to measure or specify anything regarding the
amount and size of foreign bodies left in the material that they supply.
This document describes a test method that enables the determination of the number, the size and the
substance (material) of solid contaminants in a sample of recycled material, using a small extruder and
a microscope. This test method, known as SCF (for Solid Contaminants Filtration), was developed by
a major user of recycled polyethylene and has since been in use almost daily for more than 10 years.
Although the experience gained so far with this test method is mainly with polyethylene materials, it is
believed that this method can be adapted and used for testing other thermoplastic materials.
1 Scope
This document specifies a method for determination by melt filtration of solid contaminants content in
a sample of recycled thermoplastic material, evaluating their number and, optionally, their size and
substance (material).
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.
CEN/TS 16010, Plastics — Recycled plastics — Sampling procedures for testing plastics waste and
recyclates
CEN/TS 16011, Plastics — Recycled plastics — Sample preparation
ISO 9044:2016, Industrial woven wire cloth — Technical requirements and tests
ISO 9045, Industrial screens and screening — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 9045 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
4 Principle
The material sample, normally in pellet form, is passed through an extruder fitted with a screen pack,
followed by clear, uncoloured virgin material. Then the extruder is stopped, the screen pack is taken out
and pressed flat. The screen pack is examined under a microscope for presence and evaluation of any
solid contaminants embedded in a thin layer of transparent material on the screen surface.
5 Apparatus and consumables
5.1 Extruder
A small, single-screw extruder, having screw diameter preferably between 18 mm and 30 mm, with a
breaker plate dimensioned to contain, and to enable tight clamping and complete sealing of, the screen
pack specified in 5.5.
Recommended: a convenient clamping/unclamping arrangement for the breaker plate that enables
quick and easy change of the screen pack.
NOTE Optional: a melt pressure sensor located just in front of the screen pack. A sharp and steady increase in
melt pressure while passing the tested material in the extruder is a pre-warning sign of high contamination in the
sample.
5.2 Press
A device capable of squeezing the screen pack between two parallel horizontal flat metallic surfaces,
using very low pressure, just enough to make the top layer of the hot purging material flat.
A laboratory hot press may be used for this purpose, as well as a simple manual cold press (see
Annex A, Figure A.1 for an illustration).
5.3 Microscope
A stereo (3D) zoom microscope with the following properties:
— zoom ratio: at least 5:1;
— magnification range: including 10x–50x;
— object field-of-view: at least 25 mm diameter at lowest magnification;
— millimetric measuring graticule;
— top incident cold illumination, preferably annular LED ring.
Optional: a microscope camera, linked to a measuring software.
5.4 Pointed metal rod
A sharp point metal rod (see Annex A, Figure A.2 for an illustration).
5.5 Screen pack
A two-layer screen pack, comprising two square-mesh plain-weave metal wire screens held together by
a peripheral aluminium frame: a filtering screen with aperture size 200 µm (0,2 mm), supported on a
backing screen with significantly larger aperture size, e.g. 800 µm (0,8 mm). (See Annex A, Figure A.3
for an illustration). Aperture sizes shall comply with ISO 9044:2016, Table 1.
If required, the contaminants detection threshold in this test method can be lowered or increased by
using a filtering screen with larger or smaller aperture size, respectively. Aperture sizes should be
selected in ISO 9044:2016, Table 1.
The screen pack dimensions: outer diameter (33,8 ± 0,1) mm, inner diameter (inside frame)
(28,0 ± 0,1) mm, height (thickness) at frame 1,5 mm to 1,8 mm.
NOTE These dimensions are based on EN ISO 23900-5 and fit available commercial equipment.
5.6 Plastic foil
A plastic foil that does not stick to, and does not deform when touching, the hot layer of purging
material on top of the screen pack immediately after being taken out of the extruder.
NOTE A clear polyester foil, 125 µm thick, was found to be suitable when testing polyethylene materials.
5.7 Purging material
Natural, uncoloured, transparent polymer, preferably of the same polymer family as the tested material.
For best visibility of the embedded contaminants in the layer of purging material select a material grade
with the highest transparency possible.
NOTE When testing recycled polyethylene materials, LDPE with MFI 0,2 to 0,3 was found to be suitable as
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