Alternatives

• Author: Clemm, Christan; Löw, Clara; Baron, Yifaat; Moch, Katja; Möller, Martin; Köhler, Andreas R; Gensch, Carl-Otto; Deubzer, Otmar
• Pages: 51-59

RoHS Annex II Dossier, final

TBBP-A (flame retardant)

51

8. ALTERNATIVES

The discussion on alternatives addresses the two application areas - reactive applications in PWBs

and additive applications in plastic housings.

In relation to epoxy resins (reactive use of TBBP-A in PWBs), it is understood that industry is

actively investigating substitution strategies for brominated flame retardants. The stakeholder

contributions to support this study mention that halogen-free PWB laminate materials were

available.124 However, no concrete alternatives are proposed as they would not have all necessary

safety approvals and greater percentages of the substitutes would be required within the products.

In addition, ASD state that “the substitutes are unlikely to perform sufficiently well when subjected to

heat and vibration in high-stress environments” and TMC points out that “they do not exist for all

applications, especially in high-frequency circuitry.”

Nonetheless, the most successful and already applied alternatives to TBBP-A in PWBs are phos-

phorus compounds like DOPO (9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), poly

phosphates or metal phosphinates, from time to time in combination with inorganics synergists like

ATH or silica, bound to epoxy resins. Concerning DOPO, moderate human health concern is

assumed but this compound and its derivates are expected to be highly environmental persistent.

Commonly used substitutes for TBBP-A in housings for EEE (additive use) also include halogen-

free organic phosphorus compounds. The human health hazards of the organophosphate esters are

estimated to be lower than those of TBBP-A though some substitution candidates still meet the PBT

criteria regarding the environmental risks.

In this area elimination is also possible through the substitution of polymers such as ABS and HIPS

with polymers such as PC and PPE.125

8.1. Availability of substitutes / alternative technologies

In the following information is specified summarising the potential substitutes separately presented

for reactive (see also Table 8-1) and additive (see also Table 8-2) TBBP-A applications.

Alternatives to TBBP-A in reactive applications

In relation to epoxy resins, it is understood that industry is actively investigating substitution

strategies for brominated flame retardants. In some cases, this may only entail a substitution of one

brominated flame retardant by other types rather than by bromine free alternatives. However, it is

also clear that non-halogenated flame retardants are in development for such purposes. Rakoto-

malala et al.126 mention that since disputable additives can leach out of a polymer while being

processed and/or while being used, there is always a potential health risk when such systems are

used. In addition, the environmental and end-of-life issues have led to strong efforts in replacing

halogenated systems.

124 Op. cit. TCM (2018)

125 Op. cit UBA (2008): This source specifies “this goes hand in hand with the substitution of polymers such as PC and

PPE for ABS and HIPS, or the use of polymer blends”. Semantically PC and PPE are referred to as alternatives for

both ABS and HIPS using TBBP-A. As current data suggests that only ABS is a housing material in which TBBP-A is

used, this data has been reformulated here in this respect.

126 Rakotomalala, M.; Wagner, S.; Döring, M.: Recent Developments in Halogen Free Flame Retardants for Epoxy Resins

for Electrical and Electronic Applications. Materials 2010, 3, 4300-4327; Data presented by Rakotomalala et al show

that bromine-based flame retardants account for only 10% market share of flame retardants used for EEE. Non-

halogenated substitutes account for a larger market share: metal hydroxide-based flame retardants (56%), non-

halogenated phosphorus ones (9%) and melamine-based ones (3%).