ISO/TR 21275:2017

TECHNICAL ISO/TR
REPORT 21275
First edition
2017-02
Rubber — Comprehensive review of
the composition and nature of process
fumes in the rubber industry
Caoutchouc — Examen exhaustif de la composition et de la nature des
fumées de process dans l’industrie du caoutchouc
Reference number
ISO/TR 21275:2017(E)
©
ISO 2017

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ISO/TR 21275:2017(E)

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Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Overview of the rubber industry . 8
4.1 General . 8
4.2 Rubber component production processes . 8
4.3 Generic rubber types .11
4.4 Rubber chemicals and additives .12
4.5 Mechanistic chemistry of rubber vulcanization .13
4.5.1 Generality .13
4.5.2 Sulfur-accelerated cure systems.13
4.5.3 Peroxide-based cure systems .14
4.5.4 Metal oxides .14
4.5.5 Other vulcanizing systems.14
4.6 Effect of elevated temperature on rubbery polymers and rubber additives .15
5 Definition of rubber fumes .15
6 Nature and composition of rubber fumes .16
6.1 General .16
6.2 Key components of rubber fumes and their origin .16
6.3 Trapping and analysis of rubber fumes .17
6.3.1 General.17
6.3.2 Characterization studies carried out in factory environments .17
6.3.3 Characterization studies carried out under laboratory conditions .18
6.4 Changes in rubber technology that have influenced the nature and composition of
rubber fumes and improved the protection of workers in the industry .19
6.4.1 General.19
6.4.2 Overall trend in rubber workers’ exposure to total rubber fumes .19
6.4.3 Polyaromatic hydrocarbons .19
6.4.4 Nitrosamines .19
6.4.5 Silane coupling agents and resorcinol steel cord coating agent .19
7 Factors affecting the variability of rubber fumes .19
7.1 General .19
7.2 Influence of the rubber compound formulation on the composition of rubber fumes .20
7.3 Influence of different manufacturing processes on rubber fumes .20
7.4 Influence of different processing temperatures on the composition of rubber fumes .21
8 Review of literature on the composition and nature of rubber process fumes .22
8.1 Comprehensive literature search .22
8.1.1 General.22
8.1.2 Rubber fumes data obtained from factory atmospheres .22
8.1.3 Rubber fumes data obtained by laboratory studies .32
8.1.4 Research on sampling and analysis techniques for rubber fumes.36
8.1.5 Influence of rubber additives on the composition of rubber fumes .38
8.1.6 Work carried out at Rapra Technology Ltd. .40
8.2 Other sources of information .41
8.2.1 General.41
8.2.2 Search strategy for external databases .42
8.2.3 Chemical abstracts results .42
8.2.4 General POLLUAB and NTSI database results .43
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8.2.5 Search of industry-relevant publications, government publications and
relevant websites . .43
9 Summary of the finding of the literature review .44
10 Conclusions .45
Annex A (informative) Abbreviated terms .47
Bibliography .49
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Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www . i so .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 45, Rubber and rubber products.
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ISO/TR 21275:2017(E)

Introduction
Fumes emitted during the rubber manufacturing processes were the topic of many studies. This
comprehensive study was undertaken to compile and review published data with respect to rubber
fume emissions in the workplace. This review has provided a comprehensive bank of technical data
for dissemination and further debate. It has assessed literature regarding the chemical composition
of rubber fumes in manufacturing from a comprehensive range of processes. It has been postulated
that fume emissions from rubber compound vulcanization can be considered a single chemical entity,
cited as posing a carcinogenic risk to human health. Although many studies have tried to characterize
rubber fume emissions, there is no known concise study that provides a rational explanation for this
conclusion. This study has tested this postulation and provided an insight as to whether it is a sound
conclusion.
The aim of this project was to evaluate, on a basis of sound scientific literature, whether it is
scientifically robust to consider “rubber fumes” as a homogeneous entity from a chemical point of view
and, more importantly, in relation to measurement and control of occupational exposure risk for the
rubber industry as a whole.
An extensive literature review aimed at providing a compilation of literature related to rubber fume
emissions, this study has concentrated on the chemical compositional aspects of rubber fumes only and
not on the toxicological or epidemiological aspects.
In addition, although rubber dust and rubber fumes are being considered by the EU for a potential
incorporation in the scope of the Carcinogens Directive, this study has only considered rubber fumes.
This document provides detailed information on the study carried out, the results obtained from the
literature reviews and the conclusions drawn from this information.
This document comprises two main parts; the first provides a general overview of the key areas of
rubber technology and the second provides an extensive review of in-house and external literature on
the composition and nature of rubber process fumes.
Natural rubber (NR) has been known to the civilized world since about 1493 when early European
explorers found natives of Haiti playing with balls made from the exudates of a tree called “cau-uchu”.
The term “rubber” was coined much later by the English chemist J.B. Priestly for its ability to erase
lead pencil marks. The French scientist De La Condamine first introduced NR to Europe in 1736 and
published his observations on the material in 1745. Industrial application of rubber only occurred after
Charles Goodyear in 1841 discovered the process termed “vulcanization”, which converted the rubber
to a more stable and useful material, that paved the way for the growth of the modern industry.
Synthetic rubbers were first produced in Germany in the 1930s, and during the Second World War
when the supply of natural rubber was interrupted, methods were developed for the bulk production
of synthetic rubbers. Styrene butadiene rubber (SBR) was one of the first synthetic rubbers to be
developed and manufactured in high volume in the 1940s, mainly for the production of tyres and in an
attempt to match the properties of natural rubber. Since that time, many different synthetic rubbers
have been developed to allow the use of rubber in a very wide variety of environments and applications.
Over the years, the importance of rubber to modern life has constantly increased. This is not always
immediately apparent because rubber components are often not colourful, eye catching or are used in
applications where they are not readily visible. Natural and synthetic rubber compounds are used in
a highly diverse range of rubber products which are manufactured throughout the world for various
sectors of industry and for a variety of end users, including, but not exclusively, automotive, aerospace,
medical/pharmaceutical, defence, commercial, general industrial and others.
Of the sectors where rubber is used, the automotive industry is of particular importance since tyre and
tyre products account for approximately 60 % of the synthetic rubber and ~75 % of the natural rubber
used today.
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Table 1 provides an overview of the diverse range of rubber components made from general
manufacturing processes and dipped latex technology. The list of components is by no means exhaustive
but helps highlight the diverse areas and products in which rubber is used.
Table 1 — Range of rubber components
Tyres passenger cars, trucks, racing vehicles, cycles, off-road tyres, inner tubes, curing
bladders
Conveyor/ steel cord conveyor belting, repair material for conveyor belting, scrapers, min-
Transmission belting ing conveyors, V-belts, flat belts, synchronous belts
Industrial hoses water hoses, high-pressure hoses, welding hoses, hydraulic hoses, spiral hoses,
offshore hoses, oil hoses, chemical hoses
Automotive products coolant hoses, fuel hoses, seals and gaskets, anti-vibration mounts, hydraulic
hoses, fuel injectors, timing belts, window and door channelling, transmission
and engine components, wiper blades, exhaust hangers
General mouldings/ moulded seals and gaskets, anti-vibration products, floor coverings, sheeting,
Sheeting tube rings, roofing layers, subsoil water sheeting, roller coverings, protection
linings, moulded micro-cellular products, composite profiles, rubberized fabric,
micro-cellular rubbers/profiles, wire and cable jackets and insulations, glass
sealants, pump impellors, roof membranes, pond liners, rail mounts, bridge
bearings, military vehicle track pads
Medical/ surgical gloves, medical tubing, MDI valve gaskets, catheters, dialysis products,
Pharmaceutical products surgical implants, prostheses, contraceptives, soothers, baby feeding teats and
breast caps, blood transfusion tubing and valves, medical and antistatic sheeting
and membranes, masks and respirators
Clothing boots/footwear, protective suits, household gloves, industrial gloves, footwear/
boot heels and soling, cellular rubber soles, wet suits, diving suits, coated fab-
rics, sports footwear and clothing
Food contact products food transportation (e.g. conveyer belts, hoses and tubing), food handling
(gloves), pipe and machinery components (seals, gaskets, flexible connectors and
diaphragm/butterfly valves), pumping system components (progressive cavity
pumps stators, diaphragm pumps), plate heat exchanger gaskets, seals/gaskets
for cans, bottles and closures
Potable water products pipe seals and gaskets, hoses, linings of pumps and valves, tap washers, mem-
branes in pipes and filters, coatings on process plant, tank linings
Miscellaneous products adhesives, rubberized asphalt, high vacuum and radiation components, carpet
backing, latex thread, sealants and caulking, toys
It is important that the reader of this document concludes that the rubber material used to make
any particular product is not a single entity but is a complex compounded material referred to as a
“compound” or “formulation”, which may contain a large number of essential chemical ingredients.
These ingredients will include the base rubber polymer(s), reinforcing and non-reinforcing particulate
fillers, process oils, vulcanizing agents, protective agents, process aids, etc. (all of which are available
in many types and grades from many suppliers and can be included at different levels). The company or
individual who designs a rubber formulation for a specific product has a vast number of ingredients to
choose from and as such, many formulations are therefore possible for a specific rubber product.
The processing route by which the majority of rubber components are manufactured includes mixing
the ingredients together in a controlled manner to produce a rubber “compound” or “mix”, shaping of
the mixed compound to give the desired shape or form, then “vulcanizing” (also known as “crosslinking”
and “curing”) the compound to convert it to a condition where it has permanent properties and shape.
The type of rubber materials and manufacturing processes used will depend upon the individual
product and are described in this document. Many of the manufacturing processes involve generating
heat in the rubber compound where volatile species such as “fumes” can be released from it.
The large diversity in both the rubber formulations available and the manufacturing processes used
can therefore potentially give rise to a highly diverse range of species evolved.
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In order to assist the reader to understand the terminology associated with the rubber technology in
this document, a glossary of terms is included in Annex A.
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TECHNICAL REPORT ISO/TR 21275:2017(E)
Rubber — Comprehensive review of the composition and
nature of process fumes in the rubber industry
1 Scope
This document, based on 95 publications, gives an overview of what is the composition of the fumes
emitted during the rubber manufacturing processes. The results obtained confirm that rubber fumes
are a complex and variable mix of chemicals which have a wide range of possible sources and origins,
including chemicals generated from the chemical reactions occurring in the rubber compounds during
processing and curing. Some of these chemical substances can be hazardous, others are not. This
document demonstrates the need for International Standards to qualify and quantify the hazardous
chemicals to which the operators in the factories producing rubber articles can be exposed to, allowing
the identification and mitigation of potential health risks.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
accelerator
compounding ingredient used in small amounts with a vulcanizing agent to increase the speed of
vulcanization and/or enhance the physical properties of the vulcanizate
[SOURCE: ISO 1382:2012, 2.5]
3.2
activator
compounding ingredient used in small proportions to increase the effectiveness of an accelerator
[SOURCE: ISO 1382:2012, 2.6]
3.3
ageing
exposure of a material to an environment for a period of time
[SOURCE: ISO 1382:2012, 2.13]
3.4
ageing
irreversible change of material properties during exposure to an environment for a
period of time
[SOURCE: ISO 1382:2012, 2.14]
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3.5
antidegradant
compounding ingredient used to retard deterioration by ageing
Note 1 to entry: Antidegradant is a generic term for certain additives such as antioxidants, antiozonants, waxes
and other protective materials.
[SOURCE: ISO 1382:2012, 2.21]
3.6
antioxidant
compounding ingredient used to retard deterioration caused by oxidation
[SOURCE: ISO 1382:2012, 2.24]
3.7
autoclave
pressurized vessel used for vulcanizing rubber in a vapour or gas
[SOURCE: ISO 1382:2012, 2.33]
3.8
benzene
C H
6 6
simplest member of the aromatic series of hydrocarbons
Note 1 to entry: It is colourless liquid with a b.p. of 80 °C and is used in the manufacture of many organic
compounds.
3.9
blank
piece of rubber compound of suitable shape and volume to fill the mould
[SOURCE: ISO 1382:2012, 2.44]
3.10
bonding agent
substance, usually in liquid form, coated onto another material and used to produce a good bond
between the material and rubber
[SOURCE: ISO 1382:2012, 2.54, modified — Note 1 to entry has been deleted.]
3.11
butadiene
CH CHCHCH
2 2
buta-1,3-diene
gas used in the manufacture of polybutadiene rubber and as one of the copolymers in the manufacture
of styrene-butadiene and nitrile rubbers
3.12
calender
machine with two or more essentially parallel rolls, operating at selected surface speeds, nips and
temperatures, for such operations as sheeting, laminating, skim coating (topping) and friction coating
of a product to a controlled thickness and/or controlled surface characteristics
[SOURCE: ISO 1382:2012, 2.65]
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3.13
carbon black
compounding ingredient consisting essentially of more than 95 % elemental carbon in the form of near-
spherical particles with major diameters less than 1 µm, generally coalesced into aggregates
Note 1 to entry: Carbon black is produced by incomplete burning or thermal decomposition of hydrocarbons.
[SOURCE: ISO 1382:2012, 2.66]
3.14
chlorohydrin rubbers
class of synthetic elastomers based on epichlorohydrin
3.15
chloroprene rubber
CR
elastomeric materials composed of chloroprene
Note 1 to entry: It has fair to good resistance to petroleum-based fluids and good resistance to ozone and
weathering.
[SOURCE: ISO 5598:2008, 3.2.96]
3.16
chlorosulfonated polyethylene
CSPE
elastomer made by substituting chlorine and sulfonyl chloride groups into polyethylene
Note 1 to entry: The material is best known by the trade name Hypalon (DuPont).
3.17
compound
intimate mixture of a rubber or rubbers or other polymer-forming materials with all the ingredients
necessary for the finished product
Note 1 to entry: The term rubber is sometimes used to mean compound, but this use is deprecated.
[SOURCE: ISO 1382:2012, 2.96]
3.18
compounding
development of rubber compounds which will effectively withstand the conditions under which the
products made from them are to be used
Note 1 to entry: The mixes so developed must be capable of being processed in the factory without undue
difficulty.
Note 2 to entry: The term is also applied to the assembling of elastomer and compounding ingredients ready
for mixing.
3.19
compounding ingredient
substance added to a rubber or rubber latex to form a mix
[SOURCE: ISO 1382:2012, 2.97]
3.20
compression moulding
moulding process in which the blank is placed directly in the mould cavity and compressed to shape by
closure of the mould
[SOURCE: ISO 1382:2012, 2.98]
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3.21
conveyor belting
belting used mainly in the transmission of materials, although increasing use is being made of conveyor
belting in the transportation of passengers
3.22
crosslinking
insertion of crosslinks between or within rubber chains to give a network structure
[SOURCE: ISO 1382:2012, 2.118]
3.23
curing
application of accelerators and temperature for the establishment of chemical crosslinks between
macromolecules of rubber
Note 1 to entry: This term is synonymous with vulcanization only in case of mixes containing sulfur. Some other
chemicals are also used to establish these crosslink, for example, peroxide.
Note 2 to entry: The word curing is generally paired with a specific method, e.g. press curing, open steam curing,
cold curing.
3.24
dispersion
distribution of one or more ingredients into a rubber, a rubber blend or a continuum material,
by the application of shearing forces, in order to confer optimum and uniform properties
[SOURCE: ISO 1382:2012, 2.147]
3.25
double bond
bivalent gap
ethylenic linkage
bond in which two valency bonds link two atoms in a molecule
Note 1 to entry: It is typical of compounds showing unsaturation, such as ethylene. A double bond does not
indicate extra strength of the bond but rather chemical instability and reactivity.
3.26
elastomer
macromolecular material which returns rapidly to approximately its initial dimensions and shape after
substantial deformation by a weak stress and release of the stress
[SOURCE: ISO 1382:2012, 2.161]
3.27
extender
organic material used as a replacement for a portion of the rubber required in a compound
[SOURCE: ISO 1382:2012, 2.171]
3.28
extruder
machine which, through the use of a screw or a hydraulic ram, continuously shapes a material by forcing
it through a die or dies
[SOURCE: ISO 1382:2012, 2.176]
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3.29
filler
solid compounding ingredient, in particulate form, which may be added in relatively large proportions
to a rubber or rubber latex for technical or economic purposes
[SOURCE: ISO 1382:2012, 2.184]
3.30
injection moulding
moulding process in which a rubber compound is forced into a closed mould from a separate chamber,
by a pressure which is independent of the mould clamping force
[SOURCE: ISO 1382:2012, 2.242]
3.31
internal mixer
machine with temperature controls containing one or more rotors operating in a closed cavity used to
masticate and/or to incorporate and disperse compounding ingredients into the rubber
[SOURCE: ISO 1382:2012, 2.242]
3.32
isoprene
2-methyl-1,3-butadie
...