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Task Group Co-Chairs Debra Kaiser, NIST Aleks Stefaniak, NIOSH

Task Group 1 : Methods. Task Group Co-Chairs Debra Kaiser, NIST Aleks Stefaniak, NIOSH Contributing Task Group Members (to date) Keana Scott, Tinh Nguyen, and Rick Davis, NIST Jurg Schutz , CSIRO, Australia Frank von der Kammer , University of Vienna, Austria Dermont Bouchard, EPA

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Task Group Co-Chairs Debra Kaiser, NIST Aleks Stefaniak, NIOSH

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  1. Task Group 1 : Methods Task Group Co-Chairs Debra Kaiser, NIST Aleks Stefaniak, NIOSH Contributing Task Group Members (to date) Keana Scott, Tinh Nguyen, and Rick Davis, NIST JurgSchutz, CSIRO, Australia Frank von der Kammer, University of Vienna, Austria Dermont Bouchard, EPA Technical Experts Consulted (to date) Robert Cook, Frank DelRio, Jeffrey Fagan, Justin Gorham, Angela Hight-Walker, Elijah Petersen, Keana Scott (NIST); Jeff Simpson (Towson University) NanoRelease Consumer Products: Multi-Wall Carbon Nanotube (MWCNT) in Polymers Steering Committee Workshop May 16-17, 2013

  2. Work Flow MWCNTs + polymer Materials + Products Release Processes Release scenarios MWCNT-polymer composites Release Forms of released material Driving forces Products Sampling methods Gaps and Needs Sample preparation Detection New and improved measurement methods Quantification Methods and evaluation Interlaboratory studies Characterization Measurement of Released Material Standardized methods • Sample preparation for measurement • Measurement of released material • Methods: • Generation of released material • Representative sampling NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  3. Materials and Consumer Products SEM images: A. Vladar, NIST 500 nm forming + polymer 2 µm Sporting goods Raw MWCNTs MWCNT−polymer composites • Considerations: • Polymers identified by TG2: epoxy, polyamide (PA), polyurethane (PU), polyethylene (PE), and polycarbonate (PC) • MWCNTs only form of carbon nano-objects • Products too complex • Release from MWCNT-polymer composites: two scenarios NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  4. Measurement Concepts Measurement “Hierarchy”* Measurement methods include instrument specification , procedures or well-defined protocols, data analysis and representation, and data compilation in a common format • Detection: presence (yes or no) of MWCNTs; detection limit • Quantification: number or mass concentration of MWCNTs in released material per unit volume or area of composite • Characterization: determination of characteristics and properties of MWCNTs and fragments * Adaptedfromvon der Kammeret al., Trends Anal. Chem. 2011, 30, 425-436(note: identification combinedwithdetection) NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  5. Measurement Concepts Qualitative vs. Quantitative Measurements • Qualitative • ranges from, e.g., “the sample does or does not contain MWCNTs” to “the sample contains about 50% MWCNTs” per unit area or volume examined • relative uncertainty in the estimate is large • Semi-Quantitative • measurement of, e.g., number of MWCNTs as “counted” in a sample • not all MWCNTs present may be measured (e.g., encased MWCNTs) • difficult to perform measurements that are statistically significant (e.g., tedious, representative sample) • Quantitative • measurement produces a numerical result, e.g., the diameter ranges from 100 nm to 200 nm • most MWCNTs present are measured • sufficient number of measurements to be statistically significant (can report uncertainty) • What degree of quantitation is required? * Adaptedfromvon der Kammeret al., Trends Anal. Chem. 2011, 30, 425-436(note: identification combinedwithdetection) NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  6. Release Scenario 1 • Polymer is not degraded (i.e., remains cross-linked) • Mechanical “driving force”: high energy process • Abrading, sanding, drilling… fragments: may or may not contain MWCNTs MWCNT-polymer composite MWCNTs may protrude from fragment surface, be encased in fragment, or both fragment sizes: 100 nm to 1 mm all studies report the presence of fragments only in released material fragments and unbound MWCNTs some studies report the presence of MWCNTs in released material TEM image of MWCNTs protruding from fragment Cena et al. J. Occup. Env. Hygiene. 2011, 8, 86-92. NanoRelease Steering Committee June 21-22, 2013 TG 1: Methods

  7. Release Scenario 1: Sampling Methods: Fragments • Real-time instruments • Instantaneous measures of number, mass, size, or surface area concentration • Not chemical-specific • Time-integrated samplers • Collection particles onto substrate for off-line analysis • Size-selective samplers • Separate particles by aerodynamic or other size • Can be dichotomous or multi-stage samplers: 10’s of nm to 10’s of μm • Collect particles with sizes well above the nanoscale; agglomerates • ‘Total’ (non-size-specific) samplers • Plastic cassette and conductive cowl samplers that hold filters • Precipitators (some instruments can be size-selective) NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  8. Release Scenario 1: Sampling Methods, MWCNTs • Real-time instruments are problematic • Estimate ‘equivalent’ diameter assuming spherical shape • Problems with fibers (multiple charging effects, etc.) • Time-integrated samplers as described above • Conductive cowl sampler designed for fibers • Precipitators have good efficiency in nanoscale NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  9. Release Scenario 1: What to Measure? fragments only fragments and unbound MWCNTs • All of the same to the left • Presence of unbound MWCNTs in sample (detection) • Relative amounts of fragments vs. unbound MWCNTs in sample • Number or mass concentration of unbound MWCNTs in sample • Physico-chemical characteristics or properties of unbound MWCNTs in sample, e.g., average size (diameter and length), size distribution, and surface composition • Prioritization and selection of what to measure is the essential first step • More than one measurement method is required for quantification and characterization • Sample large enough to yield a statistically relevant result (quantitative measurements) NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  10. Release Scenario 1: Measurement Methods • 12 published studies • fragments only (7); fragments and unbound MWCNTs (5) studies • Polymer: epoxy (7); PA (2), PC (2), PU (2), POM* (2), PMMA* (1) SEM and TEM most widely used measurement methods Methods for sizing fragments were not considered, except for AUC * Polymers not considered by TG2: POM  = polyoxymethlene, PMMA: Poly(methylmethacrylate) NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  11. Release Scenario 1: Method Specifications Table completed with input from NIST experts; additional input is welcome Measurement media: A = ambient; LS = liquid suspension; V = vacuum (10-6torr); UHV = ultra-high vacuum (10-9torr) NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  12. Release Scenario 1: Measured Characteristics QL , qualitative: yes/no or rough estimate SQ, semi-quantitative: can get a numerical result that is a good estimate, uncertainty is medium to high, dependent on numerous factors QN, quantitative: get a numerical result with low uncertainty NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  13. Release Scenario 1: Method Evaluation • High: statistically relevant sample size; minimal sample preparation; broadly available commercial instrument; measurement requires minimal expertise and time • Medium: unlikely that sample size is statistically relevant; moderate sample preparation; moderate availability of instruments, may contract measurements; skilled expertise and significant measurement time • Low: sample size not statistically relevant; difficult sample preparation; few instruments available at e.g., user facilities; exceptional expertise and measurement time • For detection (D), quantification (Q), and characterization (C) • High: easy to detect, quantitative result for Q and C • Medium: difficult to detect; semi-quantitative result for Q and C • Low: not used for detection; qualitative result for Q and C NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  14. Conclusions for Scenario 1 Measurement methods for released material • Must first prioritize and select key characteristics and properties of MWCNTs, in fragments and unbound, and fragments • More than one method is required to determine a characteristic or property • Numerous methods for detection of MWCNTs, unbound and in fragments • Most methods for quantification (concentration of MWCNTs) are semi-quantitative at best, i.e., may get a numerical result that is a reasonable estimate, uncertainty is medium to high • Most methods for characterization are semi-quantitative at best: • Tedious to measure a large enough amount of material for statistically relevant results • For many methods, cannot measure MWCNTs encased in a fragment • Validated protocols and reference materials essential for accurate measurements • Validation of methods and data are difficult and time-consuming NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  15. Release Scenario 2 • Polymer is chemically degraded in a binding or cross-linking sense • “Weathering”: optical (UV) and hydrolytic (humidity) “driving forces”: low energy process • Accelerated weathering by long-term exposure or by accelerated processes (e.g., the NIST “SPHERE”) tangled network of MWCNTs on the surface of the composite oligomers MWCNT-polymer composite 200 nm Peteren et al., submitted to ACS Nano potential subsequent release of unbound or tangled MWCNTs by agitation, wear, chemical reaction, or fluid flow NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  16. Release Scenario 2: What to Measure? Tangled network of MWCNTs Potential release of unbound MWCNTs • Presence of MWCNTs in release media (detection) • Number or mass concentration of unbound MWCNTs per volume of media • Physico-chemical characteristics or properties of unbound MWCNTs in media, e.g., average size (diameter and length), size distribution, and surface composition • Release media (dependent on lifecycle stage and mode of consumer use): • Environmental media: air, water, sludge, soil… • Biological media: saliva, blood, tissue • Prioritization and selection of what to measure is the essential first step • More than one measurement method is required for quantification and characterization • Sample large enough to yield a statistically relevant result (quantitative measurements) NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  17. Release Scenario 2: Measurement Methods • 8 published studies • Polymer: epoxy (2); PA (3), PU (2), POM* (1) • Methods identified below considered only tangled network resulting from polymer degradation (not subsequent release of MWCNTs or fragments by further action) SEM most widely used measurement method * Polymers not considered by TG2: POM  = polyoxymethlene NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  18. Release Scenario 2: Measured Characteristics Table completed with input from NIST experts; additional input is welcome QL , qualitative: yes/no or rough estimate SQ, semi-quantitative: can get a numerical result that is a good estimate, uncertainty is medium to high, dependent on numerous factors QN, quantitative: get a numerical result with low uncertainty NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  19. Release Scenario 2: Method Evaluation Table completed with input from NIST experts; additional input is welcome • High: statistically relevant sample size; minimal sample preparation; broadly available commercial instrument; measurement requires minimal expertise and time • Medium: unlikely that sample size is statistically relevant; moderate sample preparation; moderate availability of instruments, may contract measurements; skilled expertise and significant measurement time • Low: sample size not statistically relevant; difficult sample preparation; few instruments available at e.g., user facilities; exceptional expertise and measurement time • For detection (D), quantification (Q), and characterization (C) • High: easy to detect, quantitative result for Q and C • Medium: difficult to detect; semi-quantitative result for Q and C • Low: not used for detection; qualitative result for Q and C NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  20. Conclusions for Scenario 2 Measurement methods for tangled networks of MWCNTs • Must first prioritize and select key characteristics and properties of MWCNT networks • More than one method is required to determine a characteristic or property • Numerous methods for detection of MWCNTs • Most methods for quantification (concentration of MWCNTs) are semi-quantitative at best, i.e., may get a numerical result that is a reasonable estimate, uncertainty is medium to high • Most methods for characterization are semi-quantitative at best: • Tedious to measure a large enough amount of material for statistically relevant results • Difficult to separate tangled MWCNTs • Validated protocols and reference materials essential for accurate measurements • Validation of methods and data are difficult and time-consuming NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

  21. Recommendations • Pilot Testing and Interlaboratory Studies (ILS’s) • Start with a pilot study involving a few labs with great expertise in the topic • Possible to design a pilot test and eventually an ILS for: • Generation of released material in a controlled manner • Representative sampling of released material • Very difficult to design a pilot test for measuring MWCNTs in polymer composites that would yield reproducible results • Start with protocol development • Generation of released material by one or more specific methods • Sampling or sample preparation protocols • Protocols for qualitative or semi-quantitative measurements • Standardization of Methods • Too early! • Requires well-defined, validated protocols for any method NanoRelease Steering Committee May16-17, 2013 TG 1: Methods

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