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: 15-20

RoHS Annex II Dossier, final

TBBP-A (flame retardant)

15

2. USE IN ELECTRICAL AND ELECTRONIC EQUIPMENT

2.1. Function of the substance

The primary use of TBBP-A is as a precursor in the production of brominated epoxy resins that

function as reactively flame-retarded substrate in printed wiring boards (PWB). It is also used as an

additive flame retardant in thermoplastic EEE components, for example housings that consist of ABS

plastic. The most recent available data (2014) on proportions for the different types of application

indicate that ~90 of TBBP-A are used for the production of FR4 PWB in form of a reactive flame

retardant, while only 10 % are used as an additive flame retardant.20 However, according to

Fraunhofer ITEM IPA, Wibbertmann & Hahn (2018), the available literature data on uses varies

widely (~70-90 % reactive use).21

The following sections outline the two different forms of use in EEE products.

2.2. Types of applications / types of materials

Reactive flame retardant

As outlined in earlier works (Oeko-Institut, 2014b)22 and confirmed by stakeholders (e.g. AEM 2018;

ZVEI, 2018)23 24 more recently, the primary use of TBBP-A is as a reactive intermediate in the

manufacture of flame-retarded epoxy and polycarbonate resins.

In almost all epoxy-based PWBs of the FR4 type, TBBP-A – together with an epoxy-group containing

di-carboxylated monomer – is a precursor for the epoxy resin material. After the polymerisation, this

structure of the epoxy resin alternatingly consists of the two former monomers covalently linked via

ester or ether bonds. Therefore, reacted TBBP-A lacks its original chemical signature and the sub-

stance is unlikely to be liberated from PWBs in its original substance identity. In these uses, the

substance is chemically bound to the polymer and becomes thus an integrate part of the polymer

matrix. Hence, the chemical identity of TBBP-A is altered during the production process of EEE

components.

Regarding the chemical transformation of TBBP-A within the epoxy or polycarbonate resin formation,

it is understood from stakeholder contributions as well as from other literature that the formation of

these polymers requires (beside the epoxides and carbonates) a di-hydroxyl substituted counterpart

as a reacting agent. By default, bisphenol-A (BPA) is used as a precursor, but TBBP-A can partly

substitute the BPA in order to act as a carrier of bromine which provides the resin with flame retardant

20 Oeko-Institut (2014b): Study for the Review of the List of Restricted Substances under RoHS 2. Analysis of Impacts

from a Possible Restriction of Several New Substances under RoHS 2 by Gensch, C.-O., Baron, Y. Blepp, M.,

Bunke, D., Moch, K.

21 Op. cit. Frauenhofer ITEM IPA, Wibbertmann and Hahn (2018)

22 Op cit. Oeko-Institut 2014b

23 Association of Equipment Manufacturers (AEM; 2018): Contribution submitted during the TBBP-A 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); see the

link to the contribution in the Annex

24 Zentralverband Elektrotechnik- und Elektroindustrie e.V. (ZVEI; 2018) –Contribution submitted during the TBBP-A

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); see the link to the contribution in the Annex