Document rx6jqjvYbJLnMBd9Z2mQrj2D7

PEEK vs PTFE Analysis as a viable alternative PEEK vs PTFE polymer - Report on the analysis as a viable alternative 1. Contents 1. Contents 2. Introduction 3. Chemical Identity 4. Performance Assessment 5. Market Viability 6. Availability of PEEK 7. Economic Viability Assessment 8. Hazard and Risk Assessment 9. Assessment of other impacts 10. Acronyms 11. References Annex: detailed P and B modeling of PEEK Date: 31-May-2023 Rev: 1 Page 1 of 15 1 1 2 3 5 6 7 7 10 11 11 12 2. Introduction The purpose of this report is to inform the national authorities, with regard to the EU-REACH PFAS restriction proposals and highlight that there is an existing and viable alternative to PTFE (and other fluoropolymers such as PCTFE, PVDF) in some critical applications and in particular, in cookware and sealing applications. The existing and available alternative is PolyEtherEtherKetone Polymer, referred to as PEEK. Regarding consumer cookware, the current restrictions proposal provides: "There is sufficiently strong evidence that technically and economically feasible alternatives are widely available on the market. These include `ceramic'coatings, anodised aluminium and stainless steel (recognising that the preferred option may vary across applications). Conclusion: High substitution potential [sufficiently strong evidence}". Thus, PEEK has not been mentioned in respect to consumer cookware. As we further elaborate on below, PEEK has better mechanical properties than PTFE and it is also economically viable, refer to Section 7. This is demonstrated by the fact that there is an increasing number of cookware and sealing applications using PEEK on the EU market. PEEK is not hazardous, it is not a PBT/vPvB and it has additional environmental benefits compared to PTFE, such as recyclability and a better life cycle performance. PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 2 of 15 3. Chemical Identity of PEEK GHS Product Identifier: poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene) Trade name: Poly Ether Ether Ketone (PEEK) Polymer EC Number N/A CAS Number: 29658-26-2 and 31694-16-3 Description: Off white powder - solid Molecular Formula: (-C6H4-O-C6H4-O-C6H4-CO)n Structural Formula (repeat unit): PEEK like PTFE, is classified as a high-performance polymer. These materials exhibit high levels of performance across a range of properties, including physical, thermal, mechanical and chemical characteristics. PEEK belongs to a family of high-performance polymers called polyaryletherketones (PAEKs), which are also sometimes referred to as aromatic polyketones. Since the industrial commercialisation of PEEK polymer by ICI in the 1980s, PEEK has become the best-known and most widely-available polymer in the PAEK family. PEEK is a homopolymer, made from a predominantly linear chain of a single repeat unit with a typical average molecular weight range of 70-120,000 g/mol. The PEEK molecule contains aryl groups connected via ether bonds (-O-) and carbonyl groups (-C=O-). The polymer is semi-crystalline. This crystallinity gives rise to properties such as creep and fatigue resistance, mechanical strength at elevated temperature and generally good chemical resistance. The polymerisation of PEEK is a polycondensation reaction which takes place via a nucleophilic aromatic substitution mechanism. Two monomers, 4,4'-difluorobenzophenone and hydroquinone are reacted together in the presence of alkali metal carbonate(s). The nucleophile is created in situ via deprotonation of the hydroquinone by the alkali metal carbonate. The reaction takes place in a polar aprotic solvent, diphenylsulphone, which keeps the growing PEEK polymer in solution with the monomers as the reaction proceeds. PEEK is not classified as a PFAS, nor are PFAS or PFOA used in the polymerisation process to make PEEK. PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 3 of 15 4. Performance Assessment (Technical feasibility) Fluoropolymers such as PTFE are used in applications that require high resistance to extreme or demanding conditions. However, given the toxicological and environmental concerns related to fluoropolymers, PEEK is being increasingly used as an alternative structural and low deforming material which also has compatibility, chemical and temperature resistance and self-lubricating wear resistance, as further elaborated on below. a) Performance comparison between PEEK and PTFE A review of datasheet properties in Table 4 shows PEEK has increased mechanical properties compared to PTFE. Table 4 - datasheet properties Property Tensile strength (23C) Tensile modulus (23C) Flexural Strength Flexural Modulus Compressive strength Compressive Modulus PEEK 15,600 psi 615,000 psi 25,300 psi 600,000 psi 17,000 psi 493,000 psi PTFE 3,900 psi 80,000 psi 20,000 psi 72,000 psi 3,500 psi 70,000 psi Wear/Abrasion Performance: In a study performed by Bodycote PDL in 2008; PEEK, PTFE, FBE, and PPS polymer coatings were tested for wear on a rotating pipe with a granite slurry mix for 24 hours. The PTFE coated sample had limited remains and the coating appears to have been removed from the pipe surface by abrasion. In contrast, the PEEK coated sample had the best performance out of the four coated samples as 95% of the coating remained intact after the testing period (Mellor, 2008). In a wear evaluation of bearing materials performed by Keysight Technologies in 2014, PEEK showed less wear compared to PTFE. In this study, miniature ball bearings made of steel, PTFE reinforced with graphite, and PEEK were evaluated via various wear conditions. The study ranked the materials from best to worst as: steel, PEEK, and PTFE (Morillo, 2014). Scratch resistance: As part of their product literature, shown in table 5, Rhenotherm GmBh performed penetration depth analysis at high temperature for various polymer coatings including PEEK, PFA, PTFE, FEP, and polymer hybrids. In the report, the pure PEEK coating system displayed the lowest penetration or scratch depth of all the coating systems at high temperature (Busch). PEEK vs PTFE Analysis as a viable alternative Table 5: Rhenotherms - penetration depth at temperature Date: 31-May-2023 Rev: 1 Page 4 of 15 Impact strength: In cryogenic sealing environments, PEEK is expected to give more robust sealing performance compared to PTFE and PCTFE in conditions that require higher ductility and toughness. Table 5 below shows a study performed by Aerospace & Advanced Composites GmBH in 2015. The results show that unfilled PEEK displays 3.7 times higher impact strength than PCTFE and 2.7 times higher impact strength compared to PTFE (Scheerer, 2015) Table 6: Charpy Impact strength at -196C Key: 650G - High melt viscosity PEEK; 450G - Medium melt viscosity PEEK PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 5 of 15 Recyclability: Whilst the fluoropolymer PTFE, is classed as a thermoplastic polymer, PTFE actually behaves as a thermoset and, if irradiated, can be difficult to recycle after the original melt and shape formation. The PEEK polymer is also a thermoplastic and is able to be processed through multiple melting and cooling cycles, each time potentially being reformed into a new shape through common plastic processing methods such as injection moulding. 5. Market Viability PEEK is commercially available today in both cookware and sealing applications, and also in other applications, as outlined below. This shows that PEEK is an existing and viable alternative to PTFE. In Cookware, HUGOOD markets a PEEK Coating Non-stick frying pan on Amazon, which they claim to have exceptional abrasion resistance and is 100% free of PFAS, PFOA, GenX, APEO, lead or cadmium. - https://www.amazon.com/HUGOOD-Nonstick-Non-stick-Induction-DishwasherSafe/dp/B096NQMFCZ Ausker SRL, a cookware company based in Italy, publicly markets their PEEK Non-stick coating technology as 10 times more wear and scratch resistant compared to a PTFE 3-layer coating system, and 35 times more scratch resistant than ceramic. - https://producthype.co/the-masters-collection/ PEEK cookware coatings can also be found on the market today used in combination with PTFE coatings to increase the wear resistance of a standard PTFE coating system. Two examples are Rhenotherm and Weilburger's Greblon C3 + PEEK brand. Non-stick coatings with PEEK | Rhenotherm No.1 Coatings Cookware PTFE (greblon.com) PEEK has been used in approximately 75 million Seals in sub-sea environments which is traditionally an application for fluoropolymers. Numerous companies publicly market PEEK seals for various end market sealing applications: - ThermoFisher Scientific - Analytical applications o https://www.thermofisher.com/order/catalog/product/061687 - Green Tweed with Baker Hughes - offshore and subsea o bh-ge-harness-eu-cs.pdf (gtweed.com) - Parker Hannifin - Oil & Gas o www.parker.com/content/dam/Parker-com/Literature/Praedifa/Bulletins/API6A_PDE3504GB.pdf PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 6 of 15 Other current uses of PEEK (that may also constitute an alternative to PTFE or other fluoropolymers) include use in food, beverage, and water contact equipment as well as pharmaceutical and medical uses, including medical devices such as implantation applications. PEEK has been used in over 15 million implantable medical applications. These uses are further detailed in the Risk Assessment section below. In addition to the better creep resistance and retained ductility at low temperature of the PEEK material, it can also be used as an alternative to PCTFE in cryogenic conditions. In industrial chemical applications, PEEK is being used as an alternative to fluoropolymers such as PTFE and PVDF for applications such as reaction vessel tower packing. 6. Availability of PEEK PEEK is widely available with current availability estimated to be in the range of 8-12,000 tonnes per annum. https://www.mordorintelligence.com/industry-reports/polyether-ether-ketone-peek-market https://www.marketsandmarkets.com/Market-Reports/polyether-ether-ketone-market-928.html https://www.chemanalyst.com/industry-report/polyether-ether-ketone-peek-market- 678#:~:text=%5BOnline%20Quarterly%20Update%5D%20As%20of,CAGR%20of%203.4%25%20by%2 02035 https://www.globenewswire.com/news-release/2022/06/14/2461998/0/en/Polyether-Ether-KetonePEEK-Market-Growth-Trends-COVID-19-Impact-and-Forecast-2022-2027.html https://www.grandviewresearch.com/industry-analysis/polyether-ether-ketone-peek-industry Producers of PEEK: Evonik: state capacity of 1,500 tonnes: o EVONIK: PEEK production optimised at plant in China | Plasteurope.com Panjin Zhongrun: state capacity of 1,000 tonnes: o Pan Jin Zhongrun High Performance Polymer Co.,Ltd_COPEEK (pjzrhpp.com.cn) Solvay: estimate at 2,500 tonnes o SOLVAY: More hydroquinone capacity planned in France / Raw material for PEEK production | Plasteurope.com Victrex Manufacturing Ltd: state capacity of 7,150 tonnes: o https://wp-victrexplc-2020.s3.eu-west-2.amazonaws.com/media/2022/01/Victrex-plc-AnnualReport-2021.pdf PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 7 of 15 7. Economic viability assessment Historically, the fluoropolymers have often been favoured based on low costs. However, recently for PTFE there have been supply chain challenges post-Covid and particularly due to difficulties in obtaining a mineral used in their manufacture, called fluorspar, which is mined in Mongolia and China. Consequently, pricing for PTFE/PCTFE has fluctuated with price increases reflecting periods of high demand. When the total cost of solution is considered, then PEEK often becomes a lead candidate in material selection - since the increased performance, capability or duration of use, can off-set any initial higher cost of material. In Cookware, there is potential to reduce overall system costs with PEEK as an alternative coating to PTFE. Given the durability and abrasion properties highlighted above, a PEEK coating system may succeed with a thinner coating layer compared to PTFE, thus saving costs by using less material and reducing processing costs from building thickness with multiple coating layers. Even at the same coating thickness, less PEEK material is used due to the density of the polymers: PEEK density 1.3 gcm-3 / PTFE density 2.16 gcm-3. 8. Hazard and Risk Assessment of PEEK 8.1 Hazard Assessment As follows, from the biocompatibility data and food contact test data outlined in Section `Risk Assessment' below, PEEK is not deemed to be toxic. PEEK is not classified under the CLP Regulation. Persistent (P) and Bioaccumulation (`B') modeling of PEEK polymer using OECD QSAR ToolBox v.4.5 SP1 P and B modelling of a low molecular weight oligomer structure of PEEK (that consists of one unit of the benzophenone and two units of the benzoquinone) using the OECD QSAR ToolBox v.4.5 SP1 (latest version) has been evaluated. This oligomer provides a reasonable worst-case representative structure for estimating the potential for PEEK polymers to bioaccumulate. The results of the predictive modelling provide indication that PEEK is not likely to fulfill the criteria for "Bioaccumulative" (B) or "Very Bioaccumulative" (vB) defined in Annex XIII of the EU 1907/2006 REACH regulation. Regarding persistence, the model profile suggests that PEEK will fulfill the criteria for the "Very Persistent" ("vP") designation (and therefore, also meet the criteria for "Persistent" ("P") chemicals). Thus, it is possible to conclude that the PEEK polymers will not be classified as either PBT ("Persistent, Bioaccumulative and Toxic") or vPvB ("Very Persistent, Very Bioaccumulative"), because PEEK does not meet either B or vB criterion. In addition, it is not deemed to meet the T (toxic) criterion. A Detailed Assessment of P and B properties of PEEK is included in the Annex to this paper. In addition, the PEEK polymerization process does not intentionally add or use any PFAS (per- and polyfluoroalkyl substances) during the manufacturing process. PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 8 of 15 8.2 Risk Assessment This section contains information on biocompatibility testing, supporting the safe use of PEEK polymer in medical devices and information on food contact test data supporting the safe use of PEEK polymer intended to be used in the manufacture of materials and articles intended to come into contact with food, per European Commission Regulation (EU) No 10/2011 relating to plastic materials; US FDA Regulation 21 CFR 177.2415 for Plastics intended for Food Contact and China GB4806.6-2016: Plastic Resin for Food Contact use and GB 4806.7-2016: Plastic materials and articles for food contact use. 4.2.1 Biocompatibility PEEK comprises Polyetheretherketone. Concerning the biological evaluation for PEEK, tests have been conducted to demonstrate its biological safety and to support businesses on the adoption of this material in the manufacture of their medical devices. Implant Research Center - Handbooks - PEEK Biomaterials Handbook (drexel.edu) Details of biocompatibility testing performed on PEEK are listed in Table 1 below: Table 1: Biocompatibility testing (Supporting data available on request ) Standard ISO 10993-1 ISO 10993-3 ISO 10993-4 ISO 10993-5 ISO 10993-6 ISO 10993-6 ISO 10993-10 ISO 10993-11 ISO 10993-18 Testing Title Biological safety Genotoxicity: Bacterial Reverse Mutation Study (DMSO extract) Hemolysis Rabbit Blood Cytotoxicity Biostability study in vivo, Implantation in rabbit (90 days) and accelerated aging Long Term Femoral Bone Implantation Study of PEEK in the Rabbit ISO Maximization Sensitization Study (irritation & sensitization) USP Pyrogen Study (Systemic Toxicity) Chemical Analysis PEEK has been used since 1999 in a diverse range of applications (ex: cranio-maxillo-facial surgery, orthopaedic applications, spinal implants, etc.) and successfully used in regulatory approvals of medical devices in an extensive number of countries/regulators. As a result, numerous PEEK based devices have been used in surgical application over the last 20 years. To date, it is estimated that over 15 million devices utilizing PEEK polymers have been implanted worldwide. Most of the devices introduced to market have been manufactured through machining or milling of stock shapes into the finished parts. PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 9 of 15 4.2.2 Food contact testing Europe - Commission Regulation (EU) No 10/2011 on plastic materials and articles intended to come into contact with food. Migration tests on a number of PEEK polymer grades have been performed according to Commission Regulation No 10/2011 on specially fabricated test specimens by an independent laboratory showed that under the following conditions (Table 2) the overall migration limits and specific migration limits were not exceeded. Table 2. EU 10/2011 Simulants, times & temperatures Simulant 20% v/v aqueous ethanol 3% w/v aqueous acetic acid Fat simulant Time(s) / Temperature(s) 4 hours reflux 4 hours reflux 2 hours at 225C Supporting data available on request USA Federal Regulations Title 21: Food and Drugs; Part 177 - Indirect Food Additives: Polymers 177.2415 Poly(aryletherketone) resins. Chloroform soluble extractives testing was performed on specifically fabricated PEEK polymer test specimens per FDA 21 CFR 177.2415(c) The chloroform soluble extractives test, performed by an independent laboratory, showed that under the following conditions (table 3), the net chloroform soluble extractives specification 0.05 mg/inch (as defined within FDA 21 CFR 177.2415) was not exceeded. Table 3 - Chloroform Soluble Extractives Simulant Water 3% w/v Acetic Acid (aq) 50% v/v Ethanol (aq) n-heptane Time(s) / Temperature(s) 2 hours reflux 2 hours reflux 2 hours reflux 2 hours reflux Surface Area (inch) 32 32 32 32 Supporting data available on request PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 10 of 15 China GB 4806.6-2016 - National Food Safety Standard - plastic resins for food contact use GB 4806.7-2016 - National Food Safety Standard - plastic materials and articles for food contact use Migration tests on a number of PEEK polymer grades have been performed according to GB 4806.6 and 4806.7 on specially fabricated test specimens by an independent laboratory showed that under the following conditions (Table 4) the overall migration limits and specific migration limits were not exceeded. Table 4. GB 31604.1 Simulants, times & temperatures Simulant 95% v/v aqueous ethanol 4% w/v aqueous acetic acid Olive Oil Time(s) / Temperature(s) 4 hours reflux 4 hours reflux 2 hours at 175C Supporting data available on request. 9. Assessment of other impacts In terms of product lifecycle, a study was performed by Sphera using their GaBi software, which provides a leading Life Cycle Assessment (LCA) modelling to assess raw material processes in every phase from extraction to end-of-life. In this study, PEEK's GWP (kg CO2e/kg) was found to be very comparable to PTFE. - PEEK: 15.6 GWP (kg CO2e/kg) - PTFE: 15.3 GWP (kg CO2e/kg) The figure above is estimated using GaBI software and is based on the production of PEEK in Germany, where no PEEK is currently manufactured. PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 11 of 15 10. Acronyms PEEK - Poly Ether Ether Ketone - polymer (CAS RN: 29658-26-2 or 31694-16-3) PFAS - per- and polyfluoroalkyl substances BDF - 4,4'-Difluorobenzophenone - monomer (CAS RN: 345-92-6) HQ - Hydroquinone - monomer (CAS RN: 123-31-9) DPS - Diphenylsulphone - reaction solvent (CAS RN: 127-63-9) PTFE - Poly Tetra Fluoro Ethylene - polymer (CAS RN: 9002-84-0) CAS RN - Chemicals Abstract Service Registration Number 11. References: Table 4: external PEEK source - Arlon 1000 - GreenTweed PTFE source - https://laminatedplastics.com/teflon.pdf Mellor, Andrew (2008). Rotating Pipe Wear Testing of Various Pipe and Lining Materials. Report number: 3723/08. Bodycote Testing Limited Morillo, Carlos et all (2014). Evolution of Bearing Materials Using Nano-Scale Wear Testing. Keysight Technologies. Busch, Peter Jakob. PEEK-Systeme. Rhenotherm Kuntstoffbeschichtungs GmbH Scheerer, Michael (2015). Mechanical Testing of Thermoplastics Materials at 77k. Document No: AAC066/2014-15 Revision 1. Aerospace & Advanced Composites GmbH. PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 12 of 15 ANNEX Detailed Assessment of P and B properties of PEEK OECD QSAR ToolBox v.4.5 SP1 (latest version) was used for profiling PEEK. The following representative oligomer structure was used for the modelling: O=C(C1=CC=C(OC2=CC=C(O)C=C2)C=C1)C3=CC=C(OC4=CC=C(O)C=C4)C=C3 As presented in the ToolBox profile: Oc1ccc(Oc2ccc(cc2)C(=O)c2ccc(Oc3ccc(O)cc3)cc2)cc1 Potential bioaccumulation Log Kow (octanol-water partition coefficient) = 6.3 Water solubility (25C) = 0.497 mg/L Biotransformation half-life = 4.61 days Bioconcentration Factor (BCF) = PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 13 of 15 Regression-based estimate: 1730 L/kg wet wt Arnot-Gobas Method o Assuming no biotransformation: Upper trophic level: 20,420 L/kg wet wt o Assuming biotransformation: Upper trophic level: 1296 L/kg wet wt Mid trophic level: 1780 L/kg wet wt Lower trophic level: 1957 L/kg wet wt Thus, the estimated BCF of 1730 L/kg wet wt (which accounts for the predicted metabolic degradation/elimination of the substance in the body of the organism), indicates that the short PEEK: Is not bioaccumulative, based on EU REACH (BCF 2000 considered to be bioaccumulative; BCF 5000 considered to be very bioaccumulative) (See: http://www.chemsafetypro.com/Topics/CRA/Bioconcentration_Factor_BCF.html; "As noted For organic substances with a Log Kow value below 4.5 it is assumed that the affinity for the lipids of an organism is insufficient to exceed the bio-accumulation criterion i.e. a BCF value of 2000."). The estimate of BCF = 20,420 L/kg wet wt for upper trophic level fish, based on the assumption that the short PEEK is not metabolized in the body, is likely to be substantially over-exaggerative because the models predict that the PEEK can be metabolized and thereby, eliminated from the body. Persistence Biowin3 (Ultimate Biodegradation Timeframe): weeks to months Biowin 5 (Biodegradation probability): 0.221 Half-life o Model river: 4.82 x 1012 days = 1.32 x 1010 years o Model lake: 5.26 x 1013 days = 1.44 x 1011 years Thus, the estimated half-life in fresh and estuarine water, indicates that the short PEEK: Is Very Persistent, based on EU REACH (Degradation half-life in marine, fresh or estuarine water is higher than 60 days) As explained in the "Short PEEK Properties Summary" report (attached), an ultimate biodegradation timeframe of weeks-to-months or a Biowin 5 probability <0.5 indicates that the short PEEK is not readily biodegradable, and this is consistent with the extremely long half-lives predicted in river and lake waters. It is likely that the longer PEEK molecules (i.e. MW >398 Da <1000 Da) will be less amenable to be taken up PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 14 of 15 into the cells of simple organisms (i.e., lower trophic levels) and absorbed from the digestive systems of more complex organisms, compared with the short PEEK profiled here. However, once absorbed, these larger molecules may be more resistant to metabolism and elimination than the short PEEK. As noted in OECD (2009) (https://www.oecd.org/env/ehs/risk-assessment/42081261.pdf): "The most significant and commonly used criterion for establishing a PLC [i.e., polymers of low concern] is its Mn [i.e., number average molecular weight] range of >1000 Da. This criterion is based on the expectation that smaller molecules will more easily cross biological membranes to cause toxicity. Therefore, as the Mn of a polymer increases, a reduced incidence of potential health concern effects might be expected." "...different jurisdictions differ widely on the level of oligomeric species that are permitted in the PLC category. Some nations specify limits for just <1000 Da content, whereas others regulate both <1000 Da and <500 Da. For example:" As noted in US EPA (2013) (https://www.epa.gov/sites/default/files/2015-05/documents/06iad_polymers_june2013.pdf): "Polymers can be grouped into three categories by MWn [i.e., number average molecular weight] and LMW [i.e., low molecular weight] material composition..." "Category 1: Polymers with low molecular weight (MWn <1,000). These polymers maybe able to be assessed as a single, discrete structure in EPI Suite and ECOSAR, subject tothe normal limitation of the software. This is possible when the composition and structure of the polymer is known. In order to complete the assessment, find a reasonable representative structure of MW <1,000 and use this in the P2 modeling programs." "Category 2: Polymers with high molecular weight (MWn >1,000) and large low molecular weight (LMW) material composition (25% with MW <1,000; 10% with MW <500). These polymers can be assessed for environmental fate and toxicity as the polymer; however, oligomers may need to be assessed in addition to account for any increased toxicity due to these lower molecular weight compounds." "Category 3: Polymers with high molecular weight (MWn >1,000) and minimal LMW material (<25% with MW <1,000; <10% with MW <500). These are generally assessed solely as the polymer. However, as stated above, if a high percentage of unreacted monomers with potential health concerns are present, additional assessment may be required to address concerns for the monomer." As noted in ECETOC (2019) (https://www.ecetoc.org/wp-content/uploads/2021/10/ECETOC-TR1331CF4Polymers.pdf): PEEK vs PTFE Analysis as a viable alternative Date: 31-May-2023 Rev: 1 Page 15 of 15 "...specific properties of polymers also provide opportunities to streamline the RA process. For example, the molecular weight (Mw) distribution of a polymer product allows determining if internal bioavailability is likely. If the polymeric substance and/or polymer product are too large to pass through biological membranes, it is not meaningful to conduct higher-tier in vivo testing (while testing for local effects on e.g. skin or eyes may still be necessary). Similarly, for LMW components of the polymer product, diffusivity and migration potential from the polymer matrix determine external bioavailability e.g. at the eyes and skin, and internal (systemic) bioavailability (Step 7)." It is possible that, once absorbed, the larger molecules may be more resistant to metabolism or biotransformation and elimination than the short PEEK. Thus, the potential for a PEEK to bioaccumulate may be positively correlated with the rate of its absorption from the gastrointestinal tract and positively correlated with the MW of the polymer molecules that may be absorbed to any significant extent. However, in the absence of experimental data, the short PEEK profiled here provides a reasonable worst-case representative structure for estimating the potential for PEEK polymers to bioaccumulate." Furthermore, there is no reason to believe that longer PEEKs would be less persistent in the environment that the short PEEK profiled here.