CEN/TR 17511:2020

Materials obtained from End-of-Life Tyres - Odour of ELT granulates - Origin and remediation possibilities

The purpose of this document is to provide a review of the studies that were performed on odour of ELT granulates.

Materialien aus Altreifen - Geruch von ELT-Granulaten - Ursprungs- und Sanierungsmöglichkeiten

Matériaux produits à partir de pneus usagés non réutilisables (PUNR) - Odeur des granulats - Origine et possibilités de remédiation

Le présent document a pour objet de fournir une revue des études qui ont été menées sur l'odeur des granulats.

Materiali, pridobljeni iz izrabljenih avtomobilskih gum - Vonj granulatov ELT - Vir in možnosti sanacije

General Information

• Status: Published
• Publication Date: 07-Jul-2020
• ICS: 13.160 - Vibration and shock with respect to human beings
• Technical Committee: CEN/TC 366 - Project Committe - Tyre recycling
• Drafting Committee: CEN/TC 366/WG 3 - Composition characteristics
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 08-Jul-2020
• Due Date: 04-Sep-2020
• Completion Date: 08-Jul-2020
• Ref Project: SIST-TP CEN/TR 17511:2020 - Materials obtained from End-of-Life Tyres - Odour of ELT granulates - Origin and remediation possibilities

Overview

The CEN/TR 17511:2020 standard, titled Materials obtained from End-of-Life Tyres - Odour of ELT granulates - Origin and remediation possibilities, provides a comprehensive review of studies analyzing the odour characteristics of granulates derived from end-of-life tyres (ELT). Developed by the European Committee for Standardization (CEN), this technical report offers insight into the nature, sources, and potential treatments of odours that arise from ELT granulates during their usage, particularly relevant in applications like synthetic turf infills and thermoplastic composites.

Understanding and mitigating odour issues in ELT granulates is critical for expanding their applicability in industry and consumer products, especially where odour may be an obstacle-such as in environments exposed to elevated temperatures.

Key Topics

• Odour Determination Methods
  The standard evaluates several odour intensity assessment methods:

  • Renault D49-3001 test, a human panel-based method measuring odour intensity on a scale of 0 to 5.
  • Dynamic olfactometry, assessing odour threshold through sample gas dilution.
  • Hedonic tests, measuring odour pleasantness.
  • GC-MS olfaction test, combining gas chromatography and sensory detection to identify odorous molecules.

• Odour Origin at Different Temperatures

  • At room temperature to moderate heating (55 °C - 65 °C), odour is primarily described as “rubber-like” with acrid and acidic notes. These originate from:
    • Residual accelerators and antioxidants used in tyre manufacturing.
    • Degradation products such as benzothiazole, aniline, cyclohexylamine, and methylisobutyl ketones.
  • At higher temperatures (up to 130 °C), relevant to thermal processing like plastic injection, the acrid odour intensifies and sulphur dioxide (SO₂) becomes predominant, resulting from oxidation of vulcanization networks in the tyres.

• Odour Intensity and Molecular Characteristics

  • The report highlights that odour intensity does not directly correlate with particle size or production processes.
  • Most molecules responsible for odour emissions are volatile organic compounds (VOCs), including aldehydes, amines, acids, and sulfur compounds.

• Remediation Possibilities
  Strategies to reduce odour intensity aim to either absorb, destroy, or mask odorous compounds:

  • Absorption using zeolites or activated carbon embedded in coatings.
  • Destruction through oxidizing treatments like ozone application.
  • Washing with alkaline or solvent-based processes to remove surface residues.
  • Use of coating materials such as natural rubber or polyurethane to inhibit VOC emissions.
    The report cautions against masking odours with fragrances due to additional VOC emissions and uncertain long-term effects.

Applications

• Recycling and Reuse of ELT Materials
  CEN/TR 17511:2020 supports improving the quality and acceptability of ELT granulates used in:

  • Synthetic turf infill systems, where odour can impact user experience and acceptance.
  • Plastic compounding and injection molding applications, where granulates are exposed to high temperatures.
  • Construction materials and civil engineering, for example, rubber-modified asphalt or vibration dampening products.

• Quality Control and Certification
  The standard recommends using human-based odour evaluation methods aligned with French standard XP T47-766 for consistent and reliable odour intensity measurement, facilitating quality assessments during production and post-processing.

• Environmental and Safety Considerations
  Identification of potentially hazardous compounds such as TMQ (dihydro-trimethyl-quinoline) and sulphur dioxide informs risk management during handling and product design.

Related Standards

• EN 14243-1: Defines general terminology related to ELT materials including dimension and impurity metrics.
• AFNOR XP T47-766: French standard providing a specific method to evaluate odour intensity of ELT granulates, referenced as a procedure closely aligned with Renault D49-3001.
• International chemical terminology resources including the IUPAC Gold Book, ISO Online Browsing Platform, and IEC Electropedia for standardized definitions relevant to odour and chemical compounds.

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Keywords: End-of-Life Tyres, ELT granulates, odour intensity, volatile organic compounds, odour remediation, synthetic turf, vulcanization, plastic compounding, sulphur dioxide, benzothiazole, activated carbon treatment, tyre recycling, CEN/TR 17511:2020.

Standards Content (Sample)

SLOVENSKI STANDARD
01-oktober-2020
Materiali, pridobljeni iz izrabljenih avtomobilskih gum - Vonj granulatov ELT - Vir in
možnosti sanacije
Materials obtained from End-of-Life Tyres - Odour of ELT granulates - Origin and
remediation possibilities
Materialien aus Altreifen - Geruch von ELT-Granulaten - Ursprungs- und
Sanierungsmöglichkeiten
Matériaux produits à partir de pneus usagés non réutilisables (PUNR) - Odeur des
granulats - Origine et possibilités de remédiation
Ta slovenski standard je istoveten z: CEN/TR 17511:2020
ICS:
13.030.50 Recikliranje Recycling
83.160.01 Avtomobilske pnevmatike na Tyres in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TR 17511
TECHNICAL REPORT
RAPPORT TECHNIQUE
July 2020
TECHNISCHER BERICHT
ICS 13.160
English Version
Materials obtained from End-of-Life Tyres - Odour of ELT
granulates - Origin and remediation possibilities
Matériaux produits à partir de pneus usagés non Materialien aus Altreifen - Geruch von ELT-Granulaten
réutilisables (PUNR) - Odeur des granulats - Origine et - Ursprungs- und Sanierungsmöglichkeiten
possibilités de remédiation
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 17511:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and symbols . 5
3.1 Terms and definitions . 5
3.2 Symbols and abbreviated terms . 5
4 Determination of the intensity . 5
4.1 Methods . 5
5 Origin of the odour . 6
5.1 General . 6
5.2 At room temperature . 6
5.2.1 Description of the study . 6
5.2.2 Measured intensities for granulates . 6
5.2.3 Odour and molecular origin . 7
5.3 At higher temperature . 8
5.3.1 Description of the study . 8
5.3.2 Measured intensities for granulates . 8
5.3.3 Odour and molecular origin . 8
6 Remediation possibilities . 9
7 Conclusion and recommendations . 9
Bibliography . 10

European foreword
This document (CEN/TR 17511:2020) 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.

Introduction
The odour of ELTs granulates can be an obstacle to their use. This is particularly critical at high
temperatures, e.g. in the case of a plastic injection.
In order to solve this problem, the origin of the odour is identified to the extent that this is possible. Then
it is quantified under normal conditions of use or at higher temperatures.
The identification of the exact origin of the odour would allow the possibility of reducing or eliminating it.

1 Scope
The purpose of this document is to provide a review of the studies that were performed on odour of ELT
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, Materials obtained from end of life tyres — Part 1: General definitions related to the methods
for determining their dimension(s) and impurities
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 14243-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.2 Symbols and abbreviated terms
For the purposes of this part, the following symbols apply.
VOC Volatile Organic Compound
NR Natural Rubber
4 Determination of the intensity
4.1 Methods
In a first study [3], granulates from six different suppliers were used. The techniques that were assessed
for the determination of the intensity of the odour were the following:
— Renault D49-3001: this is one of the standardized tests for odour and smell that are commonly used
by the automotive industry. In this method, the samples in solid form are placed in a sealed container
between 70 °C and 100 °C during 2 h. A jury of at least five trained panellists then gives an intensity
on a scale from 1 to 5. The nature of the smell is then placed in a family. The scale is defined as:
— 0: no perceptible odour;
— 1: weak odour, demanding extra attention and hard to describe;
— 2: the subject perceives by simple smelling, without any other information;
— 3: odour perceived even when the attention of the subject is elsewhere;
— 4: powerful odour attracting the attention of the subject and hindering his other activities;
— 5: unavoidable odour, focusing the attention of the subject.

— Dynamic olfactometry: this is also a human-based method. The odour is diluted with a neutral gas
until it is not detected by the panellist anymore. This gives a threshold concentration.
— Hedonic test: this is also a human-based method, to assess if the odour is pleasant or not.
— GC-MS olfaction test: this is a mixed human/machine method.
...