Use in electrical and electronic equipment

• Author: Clemm, Christan; Löw, Clara; Baron, Yifaat; Moch, Katja; Möller, Martin; Köhler, Andreas R; Gensch, Carl-Otto; Deubzer, Otmar
• Pages: 19-26

RoHS Annex II Dossier, final

Diantimony trioxide (flame retardant)

19

2 USE IN ELECTRICAL AND ELECTRONIC EQUIPMENT

The terms of references define the scope of the assessment on the application of diantimony trioxide

to the use as flame retardant. Thus, several applications mentioned by stakeholders during the 1st

stakeholder consultation27 are out of scope of the assessment and will not be considered here.

Function of the substance

The function of ATO is that of a synergist for halogenated flame retardants. The International

Antimony Association (i2a) (2018)28 and the European manufacturer Campine, lead registrant for

diantimony trioxide,29 describes the function as flame retardant synergist as follows:

Diantimony trioxide (ATO) “is an additive, which functions as a synergist with halogens, to

confer high flame retardancy (and hence, fire safety) performance to plastic components

used in EEE. Halogens provide flame retardancy via the so-called “Radical Trap Mechanism”.

This is a process where reactive radicals are fed to the decomposition gas, which in turn cuts

the supply of fuel [any substance that can combust, e.g. the plastic] to the combustion region,

to cease the combustion chain reaction. The halogens released by the plastic they are

contained in, quench the chemical reaction occurring in the flame by isolating the various

factors, preventing the material from reaching its ignition temperature.

Whereas halogenated flame retardants are moderately effective on their own, they become

twice more effective when combined with ATO (in a ratio of 1:3 or 1:4). ATO effectively

enables a reduced use of halogens while increasing the flame retardancy of the plastics. […]

The use of a combined halogen + ATO flame retardant solution provides flame retardancy

via an additional “Gas phase (heat absorption and dilution) Mechanism” of flame retardancy.

The halogens with the ATO act as heat-absorbing substances which i) trigger endothermic

reactions and cool down the polymer, and ii) dilute the decomposition gas and cut the supply

of fuel to the combustion region, thereby ceasing the combustion chain reaction.”

Fire safety standards

There are different fire safety standards with different tests worldwide and the requirements depend

on the type of application / component.

Technical standards from the International Electrotechnical Commission (IEC) determine fire safety

requirements; the IEC publications with the number 60695 (“IEC 60695 Series”) cover fire hazard

testing issues, e.g. guidance for assessing the fire hazard of electr o-technical products, glowing/ hot-

27 Use as clarifying aid in certain glasses, use as opacifying agent in functional ceramics and use as catalyst in the

production of PET; see Appendix I for further explanation.

28 International Antimony Association (i2a) (2018): Contribution submitted on 15.06.2018 during the stakeholder

consultation conducted from 20 April 2018 to 15 June 2018 by Oeko-Institut in the course of the study to support the

review of the list of restricted substances and to assess a new exemption request under RoHS 2 (Pack 15);

http://rohs.exemptions.oeko.info/fileadmin/user_upload/RoHS_Pack_15/1st_Consultation_Contributions/Contribution

_i2a_diantimony_Response_ATO_20180615_FINAL.pdf, last viewed 26.06.2018

29 Campine (2018): Contribution submitted on 13.06.2018 during the stakeholder consultation conducted from 20 April

2018 to 15 June 2018 by Oeko-Institut in the course of the study to support the review of the list of restricted substances

and to assess a new exemption request under RoHS 2 (Pack 15);

http://rohs.exemptions.oeko.info/fileadmin/user_upload/RoHS_Pack_15/1st_Consultation_Contributions/Contribution

_Campine_diantimony_response_ATO_180615_non_confidential.pdf, last viewed 26.06.2018