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Environmental fate & pathways

Mode of degradation in actual use

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Administrative data

Endpoint:
mode of degradation in actual use
Remarks:
This study was performed in response to the requirements of the substance evaluation under REACH
Type of information:
experimental study
Adequacy of study:
key study
Study period:
January 2017 to January 2018
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
There is no quidleine for such a question

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
- Principle of test:
- Short description of test conditions:
Typical molding temperatures are commonly between 203 and 230 deg. C. We chose for the recycling process simualtion a higher temperature of 240 to 250 deg.C to simulate worst case conditions. Higher temperatures are not used due to known decomposition of the polymer and the flame retardant which is unwanted and therfore not a use condition. For flame retarded HIPS as for other raisins 5 to 10% of the molded resin is typically recycled back as regrind in the same process. For the analysis we used a typical composition with 12% of EBP and 4% of antimony trioxide and 6 recycling cycles were performed.
The formation of possible degradation products was investigated after each cycle using HPLC/UV and HPLC/MS methods that were further developed for this purpose.
- Parameters analysed / observed:
For this study, the Albemarle PDC Analytical Research and Quality (PARQ) department developed HPLC/UV and HPLC/MS methods to determine potential degradants of EBP in HIPS/ATO/EBP formulations. These methods were developed to meet the European Chemicals Agency (ECHA) guidelines for environmental exposure assessment, with detection limits of 0.1% relative to SAYTEX® 8010, equivalent to about 100 ppm in the HIPS/ATO/EBP formulation.

Albemarle previously developed analytical methodology to study the formation of EBP degradants in HIPS/ATO/EBP formulations during stability experiments in 2007-2010.1 The analytical methodology involved determination of the most likely degradants, nonabromodiphenylethanes (Br9’s), by HPLC/UV. The HPLC/UV methodology was developed to optimize resolution of the Br9’s from Br10. HPLC was preferred to GC for two main reasons. GC analysis would require difficult sample clean-up to separate the SAYTEX® 8010 species from the polystyrene sample matrix. Also, thermal degradation of SAYTEX® 8010 may occur during the GC analysis. Area% quantitation was used because pure Br9 standards were not available. The method involved complete dissolution of the SAYTEX® 8010 and polystyrene.

ECHA’s guidelines for environmental exposure assessment of EBP indicated the study should include a determination of potential transformation products that may form during high temperature processes such as plastic product manufacture. Potential degradants cited by ECHA include octabromodiphenylethane congeners, brominated toluenes, and brominated phenanthrenes.

We decided to continue HPLC/UV with the same sample dissolution procedure used in the earlier studies as a robust primary method to determine the potential degradants. The number of potential degradants is quite high and reference standards are not available for all compounds. Thus, we continued use of area% quantitation with a goal to determine degradants down to 0.1% relative to EBP. The original 2007 HPLC conditions, previously developed to separate Br9’s from Br10, were modified to allow separation of the additional potential degradants listed by ECHA.

An additional screening method was developed to determine brominated degradants by HPLC/MS using atmospheric pressure photoionization (APPI). Acetone is used as a mobile phase additive to enhance ionization in the negative mode. The MS technique involves detection of bromide (Br-) from fragmentation of brominated species with selected ion monitoring (SIM) to achieve the required sensitivity. This supplemental method is useful to determine possible brominated species in the presence of polystyrene oligomers or other non-brominated species that may interfere in the HPLC/UV analysis.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid

Results and discussion

Applicant's summary and conclusion

Conclusions:
Studies to mimic industrial recycling were conducted using flame-retarded high-impact polystyrene containing ethyelene-bis(pentabromophenyl) or EBP, and antimony trioxide (ATO) at 250 °C. The conditions chosen were reasoable worst case conditions for high temperature use processes , at temperatures at the high end of processing range and regrind content at the high end of recycle range. There was no observable degradation to octabrominated (or Br8) or other lower brominated species at the 100-200 ppm levels in the resin (or 1000 ppm relative to contained flame retardant). A small amount (ca. 0.2%) of reductive debromination to Br9, a common impurity in commercial EBP’s, was observed during the six molding cycles, similar to studies at lower temperatures.
Executive summary:

Studies to mimic industrial recycling were conducted using flame-retarded high-impact polystyrene containing ethyelene-bis(pentabromophenyl) or EBP, and antimony trioxide (ATO) at 250 °C. The conditions chosen were reasoable worst case conditions for high temperature use processes , at temperatures at the high end of processing range and regrind content at the high end of recycle range.  There was no observable degradation to octabrominated (or Br8) or other lower brominated species at the 100-200 ppm levels in the resin (or 1000 ppm relative to contained flame retardant).  A small amount (ca. 0.2%) of reductive debromination to Br9, a common impurity in commercial EBP’s, was observed during the six molding cycles, similar to studies at lower temperatures.