Alternatives for RoHS restricted substances

This is a guest post by Gary Nevison, Head of Legislation, Farnell, A trading division of Premier Farnell UK Ltd.

Substitution of HBCDD, DEHP, BBP and DBP

Background
UK: Hexabromocyclododecane (HBCDD), Bis-ethylhexyl phthalate (DEHP), Butyl benzyl phthalate (BBP) and Dibutyl phthalate (DBP) are classified by the REACH regulations as Substances of Very High Concern (SVHCs) and are included in the “Candidate List”. They have also been proposed for inclusion in Annex XIV, substances requiring authorisation for use.

The European Commission (EC) has submitted proposals to amend the RoHS Directive (so called RoHS2) and one proposal is to consider adding these four substances to the list of restricted substances. The three phthalates are also banned in children’s products in the European Union (EU) and in the USA.

This article describes their main uses and possible alternatives.

Main uses
Table 1: Main uses of the substancesSource: Farnell

Alternatives to HBCDD

HIPS
Two options are available; use a different brominated flame retardant or a different type of plastic. For example, decabromodiphenylethanol and ethylene bis-tetrabromophthalaimide are used as flame retardants in HIPS and can achieve UL94V0 and neither are restricted.

There are however no non-brominated flame retardants that can achieve UL94V0 in HIPS although there are several phosphorous-based flame retardants that can achieve UL94V0 in PC/ABS and PPE/HIPS blends which are often used for enclosures. However, some phosphorous flame retardants have certain hazardous properties and many are not fully tested.

Textiles
Several options are available including decabromodiphenyl ether (decaBDE) which is banned by RoHS but not in vehicles and some other applications. Chlorinated paraffins are also used but are toxic and aluminium polyphosphate which is the least hazardous option.

EPS
No alternatives exist that provide adequate flame retardancy but alternative insulation materials may be suitable. These include phenolic foams (highly persistent), polyurethane foams (very toxic fumes if burnt) and glass and mineral fibres.

XPS
No substitute flame retardants are available as all would need too high a loading and therefore the required properties of the XPS would not be met. Hence, different materials are the only alternative; starch based packaging chips and bubble wrap are two options.

Alternatives to DEHP, BBP and DBP
There are many alternatives, but most are not hazard-free and their properties differ. The following lists some of the more commonly used examples but many others are also used:

Table 2: Examples of alternatives plasticisersSource: Farnell

There are many others available including other phthalates, esters, phosphates, etc.

Conclusions
Hexabromocyclododecane, Bis-ethylhexyl phthalate, Butyl benzyl phthalate and Dibutyl phthalate are clearly hazardous chemicals so their use will, in the future, become increasingly restricted. There are many possible alternatives but choosing the best option is not straightforward. For each application, substitution will often give products with different properties and performance, which need to be assessed.

One of the main problems with choosing a substitute is to identify one that is safe to use and will not be restricted in the future. Di-isobutyl phthalate is the most common replacement for DBP but Germany has indicated that it intends to submit a proposal for di-isobutyl phthalate to be classified as a SVHC.

Most of the potential substitutes have not been extensively tested and in many cases test results are inconclusive or incomplete. However the test data that does exist for many of the possible alternatives indicates that they are safer options and many are increasingly used in preparations and in finished products.