Materials obtained from End-of-Life Tyres - Granulated rubber - Determination of textile fiber content by visual index (qualitative method)

The purpose of this Technical Report is to provide information about a procedure based on the determination of a visual index correlated with the content of textile fibers, free and bounded to the rubber, of granulates. This approach is currently used by Spanish grinders in order to control the efficiency of their processes and is effective for granulates with particle sizes whose bottom limit is higher than 0,5 mm and upper limit lower than 10 mm.

Materialien aus Altreifen - Gummigranulat - Bestimmung des Textilfasergehalts durch visuellen Index (qualitative Methode)

Matériaux produits à partir de pneus usagés non réutilisables (PUNR) - Granulats de caoutchouc - Détermination de la teneur en fibres textiles par indice visuel (méthode qualitative)

Le présent document a pour objet de fournir des informations sur un mode opératoire basé sur la détermination d'un indice visuel corrélé avec la teneur en fibres textiles, qui sont à la fois libres et liées au caoutchouc, des granulats. Cette approche est actuellement utilisée par les granulateurs espagnols pour contrôler l'efficacité de leurs procédés ; elle est appliquée aux granulats avec des granulométries dont la limite inférieure est supérieure à 0,5 mm et dont la limite supérieure est inférieure à 10 mm.
NOTE Le présent document porte également en partie sur la présentation d'une étude réalisée par Valoriza Servicios Medioambientales et Geneus Canarias S.L.
Un mode opératoire d'essai pour la détermination d'un indice visuel de la teneur en fibres textiles d'un échantillon de granulats qui est à la fois libre et lié au caoutchouc, issu de la transformation de PUNR, est décrit dans l'UNE 53936:2015 EX: Materials produced from end of life tyres. Rubber granulates.

Materiali, pridobljeni iz izrabljenih avtomobilskih gum - Granulirana guma - Ugotavljanje deleža tekstilnih vlaken z vizualnim indeksom (kvalitativna metoda)

General Information

Status
Published
Public Enquiry End Date
31-May-2020
Publication Date
26-Jul-2020
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
20-Jul-2020
Due Date
24-Sep-2020
Completion Date
27-Jul-2020

Buy Standard

Technical report
SIST-TP CEN/TR 17509:2020 - BARVE
English language
26 pages
sale 10% off
Preview
sale 10% off
Preview

e-Library read for
1 day
Technical report
kSIST-TP FprCEN/TR 17509:2020 - BARVE
English language
26 pages
sale 10% off
Preview
sale 10% off
Preview

e-Library read for
1 day

Standards Content (sample)

SLOVENSKI STANDARD
SIST-TP CEN/TR 17509:2020
01-oktober-2020
Materiali, pridobljeni iz izrabljenih avtomobilskih gum - Granulirana guma -
Ugotavljanje deleža tekstilnih vlaken z vizualnim indeksom (kvalitativna metoda)

Materials obtained from End-of-Life Tyres - Granulated rubber - Determination of textile

fiber content by visual index (qualitative method)

Materialien aus Altreifen - Gummigranulat - Bestimmung des Textilfasergehalts durch

visuellen Index (qualitative Methode)

Matériaux produits à partir de pneus usagés non réutilisables (PUNR) - Granulats de

caoutchouc - Détermination de la teneur en fibres textiles par indice visuel (méthode

qualitative)
Ta slovenski standard je istoveten z: CEN/TR 17509:2020
ICS:
13.030.50 Recikliranje Recycling
83.160.01 Avtomobilske pnevmatike na Tyres in general
splošno
SIST-TP CEN/TR 17509:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST-TP CEN/TR 17509:2020
---------------------- Page: 2 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509
TECHNICAL REPORT
RAPPORT TECHNIQUE
July 2020
TECHNISCHER BERICHT
ICS 13.160
English Version
Materials obtained from End-of-Life Tyres - Granulated
rubber - Determination of textile fiber content by visual
index (qualitative method)

Matériaux produits à partir de pneus usagés non Materialien aus Altreifen - Gummigranulat -

réutilisables (PUNR) - Granulats de caoutchouc - Bestimmung des Textilfasergehalts durch visuellen

Détermination de la teneur en fibres textiles par indice Index (qualitative Methode)

visuel (méthode qualitative)

This Technical Report was approved by CEN on 22 June 2020. It has been drawn up by the Technical Committee CEN/TC 366.

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

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 17509:2020 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

Introduction .................................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 5

2 Normative references .................................................................................................................................... 5

3 Terms and definitions ................................................................................................................................... 5

4 Principle ............................................................................................................................................................. 5

5 Apparatus ........................................................................................................................................................... 6

5.1 Splitter or sample separator ....................................................................................................................... 6

5.2 Tray ...................................................................................................................................................................... 6

5.3 Template ............................................................................................................................................................ 6

5.4 Scale ..................................................................................................................................................................... 7

6 Preparation of sampling plan and laboratory sample ....................................................................... 7

7 Procedure........................................................................................................................................................... 7

7.1 Sample spreading ............................................................................................................................................ 7

7.2 Grid counting .................................................................................................................................................... 9

7.3 Number of tests per sample ...................................................................................................................... 10

8 Expression of results ................................................................................................................................... 10

9 Preliminary studies ..................................................................................................................................... 10

10 Experimental results................................................................................................................................... 17

10.1 Grinder A (Spanish experience).............................................................................................................. 17

10.2 Grinder B (Spanish experience).............................................................................................................. 21

11 Further developments ................................................................................................................................ 25

Bibliography ................................................................................................................................................................. 26

---------------------- Page: 4 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)
European foreword

This document (CEN/TR 17509:2020) has been prepared by Technical Committee CEN/TC 366

“Materials obtained from End-of-Life Tyres (ELT)”, the secretariat of which is held by UNI.

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.

---------------------- Page: 5 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)
Introduction

During the production of materials obtained from end-of-life tires (ELTs), maintenance of quality levels

is based on the control of characteristics such as particle size distribution, steel and textile content.

Particularly important is this last parameter. Its determination can be based on the method described in

the EN 14243 series, but this test exhibits difficulties when the textile content is high and part of the fibres

are bound to the rubber.

For this reason, for granulates there is a need to define an alternative approach capable of characterizing

the content of textile fibres, free and bounded. This characterization is especially useful as a quick control

that detects quality deviations during the production process and for the acceptance of the materials by

consumers.
---------------------- Page: 6 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)
1 Scope

The purpose of this document is to provide information about a procedure based on the determination

of a visual index correlated with the content of textile fibres, which are free and bounded to the rubber,

of granulates. This approach is currently used by Spanish grinders in order to control the efficiency of

their processes and is effective for granulates with particle sizes the bottom limit of which is more than

0,5 mm, and upper limit less than 10 mm.

NOTE Part of this document is also the presentation of a study carried by Valoriza Servicios Medioambientales

and Geneus Canarias S.L.

A test procedure for the determination of a visual index of the content of the textile fibre of a granulate

sample, which is free and bounded to the rubber, from the ELT’s processing is described in

UNE 53936:2015 EX: Materials produced from end of life tyres. Rubber granulates.
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.

EN 14243-1:2019, Materials obtained from end of life tyres - Part 1: General definitions related to the

methods for determining their dimension(s) and impurities
3 Terms and definitions

For the purposes of this document, terms and definitions given in EN 14243-1:2019 and the following

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 http://www.iso.org/obp
3.1
bounded textile

textile fraction on the granulate, that is bounded to the rubber and that cannot be separated without

pulling rubber particles with it
3.2
visual index

conventional value, expressed in %, that correlates with the content of textile in a sample of granulate

and is obtained through a mechanical device and the visual control of an operator

Note 1 to entry: 0 % index means absence of textile, 100 % a presence of textile in all the parts of the device of

control.
4 Principle

The determination of textile fibres, which are free and bounded to the rubber, of an ELT sample of

granulates, is based on the calculation of a visual index.

The underlying method is based on the recount of textile particles detectable to the naked eye in a sample

distributed over the surface of a tray. To make the calculation easy, a grid template is placed over each

sample.
---------------------- Page: 7 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)

The visual index is the ratio between the number of cells in which one textile is detected to the naked eye

with respect to the total number of cells on the grid template.
5 Apparatus
5.1 Splitter or sample separator

The most used one is the riffle splitter: the sample separator shall contain at least 16 slots, located

alternately so they send the material to two different subsamples. The width of the slots shall be at least

three times the upper nominal size of the material to be divided in order to avoid the bridge effect.

5.2 Tray

Square or rectangular tray, rigid with flat surface and an area of (1 500 ± 50) cm , of any material,

provided that it does not bound or interact with the rubber. See Figure 1.
Figure 1 — Example of tray
A tray of 30 cm x 50 cm that matches with a 375 grids template is recommended.
5.3 Template

Square or rectangular template of geometry equivalent to the surface of the tray, divided on 2 cm x 2 cm

cells and that do not prevent the proper visualization of the sample. See Figure 2.

Figure 2 — Example of template
---------------------- Page: 8 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)
5.4 Scale
Scale capable of measuring the mass of the sample with an estimate within 0,1 g.
6 Preparation of sampling plan and laboratory sample

The base is a representative sample obtained from moving material in production or from storage

material on a big-bag. The sample is divided with a splitter until obtaining a mass of 500 g ± 5 g.

7 Procedure
7.1 Sample spreading

The sample to test is placed on the tray and then the material is evenly distributed across its surface, see

Figure 3.
Figure 3 — Sample placed on the tray

To allow the various free and bound textile particles come to the surface, the tray shall be hit against the

work surface five times, as illustrated in Figures 4 and 5.
---------------------- Page: 9 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)
Figure 4 — Example of the hitting process
Figure 5 — Sample spreaded on the tray
Hereafter the template mentioned in 5.3 is placed on it, see Figure 6.
---------------------- Page: 10 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)
Figure 6 — Template placed on the tray
7.2 Grid counting

A counting of the cells where free or bound textile is visually detected is performed (see Figures 7 and 8),

and the value obtained is written down.
Figure 7 — Grid counting process
---------------------- Page: 11 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)
Figure 8 — Example of the cells where free or bound textile is visually detected
7.3 Number of tests per sample

Once performed the recount, the template is withdrawn. The tray is emptied and the sample is poured on

it again. The operating procedure is repeated according to 7.1 and 7.2. The results are written down. The

procedure is repeated until obtaining three values of the same sample.
8 Expression of results
The visual index comes from the equation:
Visual index = 𝑁𝑁 /𝑁𝑁 x 100 [1]
𝑓𝑓
where

𝑁𝑁 average value obtained from the three measurement of the grid number in which is

𝑓𝑓
detected the presence of textile fibre
N total number of cells on the template
The value rounded upward is established as the result of the visual index.
9 Preliminary studies

Some preliminary tests have been carried out in order to study the effect of the following parameters:

— Cell size;
— Number of tests per sample;
— Tray area/ Sample thickness;
— Textile content.

In the preliminary studies, several samples with known quantity of free and bounded textile particles

were prepared. This way, it could be compared the results obtained in the different conditions respect to

the reference value in each case, see Figure 9.
---------------------- Page: 12 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)
a) Free textile particles b) Bounded textile particles
Figure 9 — Examples of free and bounded textile particles
A summary of tests performed by SIGNUS, are described below.
— Effect of the cell size:

First of all, it is important to note the grid size of the template. Some tests have been performed in

order to define the cell optimum size, see Figure 10.
---------------------- Page: 13 ----------------------
SIST-TP CEN/TR 17509:2020
CEN/TR 17509:2020 (E)
Key
X number of textile particles in the sample
Y visual index (%)
Reference
No grid
Grid size 2 cm
Grid size 4 cm
Grid size 8 cm
Figure 10 — Effect of the cell size (diameter)

The values corresponding with 2 cm of the cell size are equivalent to the reference and also for those

obtained without grid. That is the reason why it is decided to fix the cell diameter of 2 cm.

— Effect of the number of tests per sample:

A simulation for 3 and 6 measures has been done in order to define the tests number. The average

value of visual index is equivalent for both cases, as it is shown below, see Table 1 and Figure 11.

Table 1 — Results correspondent study of effect of the number of tests per sample

Particle size of granulate: 2 - 4 mm
Average value of Average value
...

SLOVENSKI STANDARD
kSIST-TP FprCEN/TR 17509:2020
01-junij-2020
Materiali, pridobljeni iz izrabljenih avtomobilskih gum - Granulirana guma -
Ugotavljanje deleža tekstilnih vlaken z vizualnim indeksom (kvalitativna metoda)

Materials obtained from End-of-Life Tyres - Granulated rubber - Determination of textile

fiber content by visual index (qualitative method)

Materialien aus Altreifen - Gummigranulat - Bestimmung des Textilfasergehalts durch

visuellen Index (qualitative Methode)
Ta slovenski standard je istoveten z: FprCEN/TR 17509
ICS:
83.160.01 Avtomobilske pnevmatike na Tyres in general
splošno
kSIST-TP FprCEN/TR 17509:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
kSIST-TP FprCEN/TR 17509:2020
---------------------- Page: 2 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FINAL DRAFT
TECHNICAL REPORT
FprCEN/TR 17509
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
February 2020
ICS
English Version
Materials obtained from End-of-Life Tyres - Granulated
rubber - Determination of textile fiber content by visual
index (qualitative method)
Materialien aus Altreifen - Gummigranulat -
Bestimmung des Textilfasergehalts durch visuellen
Index (qualitative Methode)

This draft Technical Report is submitted to CEN members for Vote. It has been drawn up by the Technical Committee CEN/TC

366.

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.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a Technical Report. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a Technical Report.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TR 17509:2020 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

Introduction .................................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 5

2 Normative references .................................................................................................................................... 5

3 Terms and definitions ................................................................................................................................... 5

4 Principle ............................................................................................................................................................. 5

5 Apparatus ........................................................................................................................................................... 6

5.1 Splitter or sample separator ....................................................................................................................... 6

5.2 Tray ...................................................................................................................................................................... 6

5.3 Template ............................................................................................................................................................ 6

5.4 Scale ..................................................................................................................................................................... 7

6 Preparation of sampling plan and laboratory sample ....................................................................... 7

7 Procedure........................................................................................................................................................... 7

7.1 Sample spreading ............................................................................................................................................ 7

7.2 Grid counting .................................................................................................................................................... 9

7.3 Number of tests per sample ...................................................................................................................... 10

8 Expression of results ................................................................................................................................... 10

9 Preliminary studies ..................................................................................................................................... 10

10 Experimental results................................................................................................................................... 17

10.1 Grinder A (Spanish experience).............................................................................................................. 17

10.2 Grinder B (Spanish experience).............................................................................................................. 21

11 Further developments ................................................................................................................................ 25

Bibliography ................................................................................................................................................................. 26

---------------------- Page: 4 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)
European foreword

This document (FprCEN/TR 17509:2020) has been prepared by Technical Committee CEN/TC 366

“Materials obtained from End-of-Life Tyres (ELT)”, the secretariat of which is held by UNI.

This document is currently submitted to the Vote on TR.
---------------------- Page: 5 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)
Introduction

During the production of materials obtained from end-of-life tires (ELTs), maintenance of quality levels

is based on the control of characteristics such as particle size distribution, steel and textile content.

Particularly important is this last parameter. Its determination can be based on the method described in

the EN 14243 series, but this test exhibits difficulties when the textile content is high and part of the fibres

are bound to the rubber.

For this reason, for granulates there is a need to define an alternative approach capable of characterizing

the content of textile fibres, free and bounded. This characterization is especially useful as a quick control

that detects quality deviations during the production process and for the acceptance of the materials by

consumers.
---------------------- Page: 6 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)
1 Scope

The purpose of this document is to provide information about a procedure based on the determination

of a visual index correlated with the content of textile fibres, which are free and bounded to the rubber,

of granulates. This approach is currently used by Spanish grinders in order to control the efficiency of

their processes and is effective for granulates with particle sizes the bottom limit of which is more than

0,5 mm, and upper limit less than 10 mm.

NOTE Part of this document is also the presentation of a study carried by Valoriza Servicios Medioambientales

and Geneus Canarias S.L.

A test procedure for the determination of a visual index of the content of the textile fibre of a granulate

sample, which is free and bounded to the rubber, from the ELT’s processing is described in

UNE 53936:2015 EX: Materials produced from end of life tyres. Rubber granulates.
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.

EN 14243-1:2019, Materials obtained from end of life tyres - Part 1: General definitions related to the

methods for determining their dimension(s) and impurities
3 Terms and definitions

For the purposes of this document, terms and definitions given in EN 14243-1:2019 and the following

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 http://www.iso.org/obp
3.1
bounded textile

textile fraction on the granulated, that is bounded to the rubber and that cannot be separated without

pulling rubber particles with it
3.2
visual index

conventional value, expressed in %, that correlates with the content of textile in a sample of granulate

and is obtained through a mechanical device and the visual control of an operator

Note 1 to entry: 0 % index means absence of textile, 100 % a presence of textile in all the parts of the device of

control.
4 Principle

The determination of textile fibres, which are free and bounded to the rubber, of an ELT sample of

granulates, is based on the calculation of a visual index.

The underlying method is based on the recount of textile particles detectable to the naked eye in a sample

distributed over the surface of a tray. To make the calculation easy, a grid template is placed over each

sample.
---------------------- Page: 7 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)

The visual index is the ratio between the number of cells in which one textile is detected to the naked eye

with respect to the total number of cells on the grid template.
5 Apparatus
5.1 Splitter or sample separator

The most used one is the riffle splitter: the sample separator shall contain at least 16 slots, located

alternately so they send the material to two different subsamples. The width of the slots shall be at least

three times the upper nominal size of the material to be divided in order to avoid the bridge effect.

5.2 Tray

Square or rectangular tray, rigid with flat surface and an area of (1 500 ± 50) cm , of any material,

provided that it does not bound or interact with the rubber. See Figure 1.
Figure 1 — Example of tray
A tray of 30 cm x 50 cm that matches with a 375 grids template is recommended.
5.3 Template

Square or rectangular template of geometry equivalent to the surface of the tray, divided on 2 cm x 2 cm

cells and that do not prevent the proper visualization of the sample. See Figure 2.

Figure 2 — Example of template
---------------------- Page: 8 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)
5.4 Scale
Scale capable of measuring the mass of the sample with an estimate within 0,1 g.
6 Preparation of sampling plan and laboratory sample

The base is a representative sample obtained from moving material in production or from storage

material on a big-bag. The sample is divided with a splitter until obtaining a mass of 500 g ± 5 g.

7 Procedure
7.1 Sample spreading

The sample to test is placed on the tray and then the material is evenly distributed across its surface, see

Figure 3.
Figure 3 — Sample placed on the tray

To allow the various free and bound textile particles come to the surface, the tray shall be hit against the

work surface five times, as illustrated in Figures 4 and 5.
---------------------- Page: 9 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)
Figure 4 — Example of the hitting process
Figure 5 — Sample spreaded on the tray
Hereafter the template mentioned in 5.3 is placed on it, see Figure 6.
---------------------- Page: 10 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)
Figure 6 — Template placed on the tray
7.2 Grid counting

A counting of the cells where free or bound textile is visually detected is performed (see Figures 7 and 8),

and the value obtained is written down.
Figure 7 — Grid counting process
---------------------- Page: 11 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)
Figure 8 — Example of the cells where free or bound textile is visually detected
7.3 Number of tests per sample

Once performed the recount, the template is withdrawn. The tray is emptied and the sample is poured on

it again. The operating procedure is repeated according to 7.1 and 7.2. The results are written down. The

procedure is repeated until obtaining three values of the same sample.
8 Expression of results
The visual index comes from the equation:
Visual index = 𝑁𝑁𝑓𝑓/𝑁𝑁 x 100 [1]
where

𝑁𝑁𝑓𝑓 average value obtained from the three measurement of the grid number in which is

detected the presence of textile fibre
N total number of cells on the template
The value rounded upward is established as the result of the visual index.
9 Preliminary studies

Some preliminary tests have been carried out in order to study the effect of the following parameters:

— Cell size;
— Number of tests per sample;
— Tray area/ Sample thickness;
— Textile content.

In the preliminary studies, several samples with known quantity of free and bounded textile particles

were prepared. This way, it could be compared the results obtained in the different conditions respect to

the reference value in each case, see Figure 9.
---------------------- Page: 12 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)
a) Free textile particles b) Bounded textile particles
Figure 9 — Examples of free and bounded textile particles
A summary of tests performed by SIGNUS, are described below.
— Effect of the cell size:

First of all, it is important to note the grid size of the template. Some tests have been performed in

order to define the cell optimum size, see Figure 10.
---------------------- Page: 13 ----------------------
kSIST-TP FprCEN/TR 17509:2020
FprCEN/TR 17509:2020 (E)
Key
X number of textile particles in the sample
Y visual index (%)
Reference
No grid
Grid size 2 cm
Grid size 4 cm
Grid size 8 cm
Figure 10 — Effect of the cell size (diameter)

The values corresponding with 2 cm of the cell size are equivalent to the reference and also for those

obtained without grid. That is the reason why it is decided to fix the cell diameter of 2 cm.

— Effect of the number of tests per sample:

A simulation for 3 and 6 measures has been done in order to define the tests number. The average

value of visual index is equivalent for both cases, as it is shown below, see Table 1 and Figure 11.

Table 1 — Results correspondent study of effect of the number of tests per sample

Particle size of granulate: 2 - 4 mm
Average value of Average value of
Lot Measure Measure Measure Measure Measure Measure Visual Index Visual Index
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.