An opinion article published on December 7, 2018, by regulatory news provider Chemical Watch, addressed “dealing with polymers under REACH.” Paul Ashford, managing director at Anthesis-Caleb consultancy, observes that “the regulatory focus has turned again towards polymers,” however, “concerns should be focused on single-use plastics, where the throw-away culture is seen at its worst.” Further, there are “increasing calls for a circular economy, but this is not yet happening to the extent it should, primarily because of the lack of regulation or financial incentive.” The regulatory situation “is made even more difficult by the complexity of the polymer arena,” as “the number in commerce is estimated at between 400,000 and over one million.”
A major focus is on the environmental fate of polymers with “particular concern emerging from microplastics and microfibers.” While sources of secondary microplastics are “almost intractable,” current regulatory actions in the European Union aim to target “the intentional addition of plastic microbeads” (FPF reported), and recommendation by the European Chemicals Agency on this matter is expected “as early as January 2019.”
Ashford observes that this development has come as a surprise “to the European polymer industry and its supply chain,” because here “a chemical regulation [(i.e, REACH) is] in effect being leveraged to address a physical environmental challenge.” Similar trends “in the use of REACH to address the physical characteristics of materials in human health” were followed “with the classification of hazards relating to poorly soluble particulates,” Ashford recalls. However, in his opinion, “this raises the question about whether a substance-based regulation like REACH can be used to address classes of materials like plastics and particulates.”
The “debate on the definition [of microplastics] is still ongoing” within REACH. Most of this debate “has focused on physical form,” while “little attention has been paid to the chemical composition outside of biodegradability and source.” In 1993, the Organization for Economic Cooperation and Development (OECD) has introduced “a global definition for a polymer.” However, this “only added to the complexity of the challenge,” Ashford comments, because it resulted in “the creation of a class of substances previously considered to be polymers, now being classed as ‘no longer polymers’ (NLPs).”
Ashford further explains that “most polymers in commerce are sold as mixtures: thermoplastics have additives like antioxidants, UV-stabilizers, plasticizers and flame retardants, while thermosetting (reactive) polymers are likely to have solvents, catalysts and other reactive species to facilitate further polymerization at later stages of the value chain.” The OECD definition “only addresses the polymer component of such mixtures.” Historically throughout the world, “the need to distinguish between polymers as defined by the OECD and polymeric mixtures as sold on the market” has been “glossed over.” However, REACH “forced a more rigorous investigation because of the need to decide what a ‘polymer substance’ is in order to align with the Regulation’s approach at substance level.”
The consultations on the first version of a REACH guidance for polymers, issued by ECHA in 2007, were dominated by the thermoplastics industry. This sector was “understandably less concerned about residual monomers in its polymers, since these were typically present at very low levels.” They were therefore “considered to be impurities and, in line with the REACH substance definition, part of the polymer substance.” Fully cured thermoset matrices can be treated similarly, because there “the residual monomers would be at very low levels too,” Ashford states. However, thermosetting resins that are intended to undergo further polymerization during the final article production do contain higher levels of monomers as a result, but these are there not as impurities, but as substances intended to perform a technical function. The polymer guidance reissued by ECHA in 2012 did not manage, however, “to reconcile the two interpretations.”
Therefore, in 2014, industry trade association Cefic negotiated “an informal agreement [between thermoset and thermoplastic polymer companies] on the distinction between a ‘residual monomer’ (with no technical function) and an ‘unreacted monomer’ (with one).” The former would be considered “an impurity in the polymer substance,” while the latter “would be a component in a polymer mixture.” In this way, thermoplastic polymers would be treated as ‘substances,’ while thermosetting polymers still containing unreacted monomers to be polymerized at a later stage would be treated as ‘mixtures.’ During processing along the value chain, thermosetting polymer mixtures typically become “less and less hazardous as MW [(molecular weight)] increases and other mixture components, such as unreacted monomers, are consumed,” Ashford explains. However, “the regulatory challenge arises because there is no current way of delineating low MW polymers from high MW polymers of the same chemistry.”
Several REACH-commissioned studies have been carried out addressing the issue of polymer identity. The “latest initiative” by the European Commission (EC) seeks “to determine the criteria for ‘polymers of concern.’” This, in Ashford’s opinion, “stresses even more the need for clarity on how polymer substances are identified.” The EC’s study has three aims, namely (i) “to find criteria based on hazard properties and exposure for deciding whether a polymer is of concern or not,” (ii) “to look at ways of grouping polymers,” and (iii) “to find the appropriate information requirements for polymers of concern (also in the function of tonnage bands).” However, a “clear guidance on the substance identity question” would be needed “before even starting to determine the hazard and exposure properties of the polymers being considered.” There is also “a need to cross-read between information obtained on polymers ‘as sold’ (typically mixtures, even for thermoplastics where additives are used) and the hazard profiles of the substances themselves,” Ashford suggests.
In his concluding thoughts, Ashford emphasizes that “REACH imposes a level of substance specificity on chemicals not seen in other comparable regulations.” When applied to polymers, this “will require very clear guidance on how a substance is identified,” in particular because “while thermoplastics are the dominant form in terms of volume, thermosetting and other reactive polymers are dominant in number.” Hence, a key issue would concern “the naming of reactive systems,” which is “likely to require going beyond the existing CAS framework.” Ashford calls on the experts working on the ongoing EC’s polymer study “to address this early in development.” The study is anticipated to run “until the end of 2019,” but “industry experience suggests that discussions on polymer identity at substance level may take much longer.” This is because “the challenges are very different to those posed by the wider plastics discussion, which is focused solely on physical characteristics,” and it would be “important not to confuse or conflate the two issues.”
Read more
Paul Ashford (December 7, 2018). “Dealing with polymers under REACH.” Chemical Watch
Chemical Watch (May 10, 2018). “EU seeks proposal for ‘polymers of concern’ project.”
