Characterisation of nanomaterial release during their lifecycle

Transcription

1 Faculty of Mechanical Science and Engineering Institute of Process Engineering and Environmental Technology Research Group Mechanical Process Engineering Characterisation of nanomaterial release during their lifecycle Michael Stintz Institute of Process Engineering and Environmental Technology, Research Group Mechanical Process Engineering Regulatory Challenges in Risk Assessment of Nanomaterials Topic 2: Measurement and characterization of nanomaterials Topical Scientific Workshop, ECHA, Helsinki, /24

2 First defined Release from powders ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 2

3 Nanoparticle Release Testing Published studies on nano-object release into air suffer more or less from three problems, i.e. a consistent terminology, standardized metrological procedures and the kind of data evaluation. Thus, a quantitative comparison between the different studies was often impossible, if necessary parameters are missing. This hinders also the conclusion on real exposure situations. To fill this gap, ISO/TC 229/JWG 2/PG 10 has developed in a first step the technical specification ISO/TS 12025:2012, which is a general framework for determining airborne release of nano-objects from nanostructured powders by means of aerosol analysis. The TS provides information on the methodology for nano-object release quantification that covers beside necessary measurands and process parameters also the presentation of measurement results by specific release numbers. It supports also standardization of nano-object release testing of nanocomposites, e.g. by abrasion procedures. ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 3

4 Definition of Nanoparticle Release ISO/TS 12025:2012, Nanotechnologies Quantification of nano-object release from powders by generation of aerosols Symbol Quantity SI Unit n nano-object number release dimensionless n t nano-object release rate s -1 c n nano-object aerosol number concentration m -3 n m mass specific nano-object number release kg -1 V t aerosol volume flow rate m 3 s -1 nano-object number release total number of nano-objects, released from a sample as a consequence of a disturbance nano-object release rate total number of nano-objects, released per second as a consequence of a disturbance mass specific nano-object number release Nano-object number release, divided by the mass of the sample before the disturbance ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 4

5 Nanoparticle Release from Powders Compressed dry air Compressed dry air Valve Valve Informative Example Vortex Shaker method Flow meter Flow meter HEPA filter HEPA filter Dilution 15 μm cut 2.5 μm cut Cyclone APS OPC DMA w/ neutralizer SMPS CPC Cyclone Vortex Shaker CPC Make-up air Excess HEPA filter HEPA filter Flow meter Valve Pump

6 Workplace Measurement Limits from workplace background: Koponen IK, Jensen KA, Schneider T: Sanding dust from nanoparticlecontaining paints: physical characterisation. J Phys: Conf Ser 2009, 151: Kuhlbusch et al.: Nanoparticle exposure at nanotechnology workplaces: A review, Göhler, Stintz: 4. Nanoparticle release studies under laboratory conditions Particle and Fibre Toxicology 2011, 8:22 ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 6

7 Nanocomposites testing under lab conditions ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 7

8 1. Test Setup TUD Abrasion test under particle free atmosphere Taber Abraser for stressing samples Detection of aerosol particle emission with SMPS Additional, microscopic investigations CEFIC Workshop June 2008 in Brussels: J. Aerosol Science, 2009, Vol 40, No 3, pp Vorbau M, Hillemann L and Stintz M, TU Dresden: Method for the characterization of the abrasion induced nanoparticle release into air from surface coatings Nr. 8

9 1. Test Setup CEA Nanosafe November 2008 in Grenoble: Journal of Physics: Conference Series 170 (2009) Arnaud Guiot, Luana Golanski and François Tardif CEA-Liten: Measurement of nanoparticle removal by abrasion Nr. 9

10 General Release Test Cycle, e.g. Sanding nanoparticle release characterization for exposure assessment no harmonized methodology data comparability is very limited complex metrological challenge sample preparation aerosol generation aerosol conditioning aerosol analysis data evaluation sample selection sample supply aerosol sampling measurands type of quantity sample conditioning sample treatment background aerosol instruments transferability characterization aerosol sampling phys. & chem. prop. type of quantity comparability objective risk assessment by systematic exposure characterization in laboratory qualitative & quantitative particle release characterization (Göhler et. al. 2010) 2 projects based on sanding of artificially aged/weathered nano-composites Göhler, Stintz et al. Journal of Physics: Conference Series 429 (2013) ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 10

11 Nanoparticle Release Test - Sanding Materials - Sample preparation & conditioning Project A sample production / preparation coatings: squeegee application oak, alumina, fiber cement substrates sample conditioning artificial aging (EN 927-3:2006, dry) UV-A radiation (351 nm) without irrigation duration: 2000 h (PU A, UV A, AC A ) Project B sample production / preparation squeegee application on alumina (coatings) injection molding (composites) sample conditioning artificial weathering (ISO 11341:2004) filtered xenon arc radiation ( nm) 102 min illumination & 18 min irrigation duration: 2500 h (AC B ) / 2000 h (PP B ) Q-UV controller UVA-Lamps detectors Xenotest Beta LM sample chamber blower heater humidifier blower filter ventilation circuit xenon-arc lamp cooling ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 11

12 Nanoparticle Release Test - Sanding Materials - Sample characterization Project A sample surface analyses specular gloss measurement SEM-analyses sample surface condition darkening of non-doped PU A, UV A brightening of ZnO-doped coatings delamination of PU A (alumina) Project B sample surface analyses specular gloss measurement SEM-analyses sample surface condition PP B showed crack formation with isolated matrix fragments and deeper penetration (50 µm-250 µm) as AC B non aged part PU PU* PU-ZnO PU*-ZnO PU-Fe 2 O 3 PU*-Fe 2 O 3 non-weathered surface weathered surface aged part sample cross section (50 x) ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 12

13 Nanoparticle Release Test - Sanding Experimental details - Experimental apparatus sanding process apparatus of Göhler et al. (2010) particle free environment sampling of all emissions sampling at particle source process parameters 2010: industrial sanding process project A: comparability with 2010 project B AC B : sanding only within weathered region of the samples (< 5 µm) project B PP B : avoidance of thermal particle generation parameter 2010 A B SC SC AC B PP B sanding area [cm²] sample speed [mm/min] sanding time [s] face velocity [m/s] normal force [N] paper graining [-] P600 P600 P1200 P240 rotational velocity [m/s] cutting velocity ratio [-] cutting power [W] Göhler et al. (2010) Ann. Occup. Hyg.; 54(6): ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 13

14 Nanoparticle Release Test - Sanding Results - Data evaluation aerosol measurement data particle number concentration without additional information not suitable as release parameter number-weighted particle size distributions independent release parameter fractional particle release numbers n A (e.g. x 100 nm, x< 10 µm, x 1 µm) relation to stressed area area specific release numbers [ (particles 100 nm) /cm²] c n q 0 * = dcn /dlogx [cm -3 ] E E+03 EEPS 1.6E+03 APS 1.60E E E E+02 aerodynamic particle diameter [µm] 1.20E E E E E electrical mobility diameter [µm] Göhler, Stintz et al. Journal of Physics: Conference Series 429 (2013) ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 14

15 Now ISO/TC 256 Standardization project ISO/TC 256 NWIP:2014 Pigments and extenders Determination of experimentally simulated nano-object release from paints, varnishes and pigmented plastics Scope This standard specifies a method for experimental determination of the release of nanoscale pigments and extenders into the environment following an abrasive stress of paints, varnishes and pigmented plastics. The method is used to evaluate if and how many particles of defined size and distribution under stress (type and height of applied energy) are released from surfaces and emitted into the environment. The samples may be aged, weathered or otherwise conditioned to simulate the whole lifecycle. ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 15

16 Nanoparticle Release Test - Spraying Göhler, Stintz: Granulometric characterization of airborne particulate release during spray application of nanoparticle-doped coatings. J Nanopart Res (2014) 16:2520 ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 16

17 Nanoparticle Release Test - Spraying compressed air supply 2.5 bar P HEPAfilter spray module (no. 2) spray-channel HEPAfilter HEPAfilter VKL 10 VKL 10 MFM M40211 HEPAfilter exhaust, atmospherically decoupled two-way stopcock Kr Kr HEPAfilter blower 400 L min -1 P 2.5 bar 2.5 bar 0.3 L min L min -1-3 kv / +13 kv ESP flow splitter EEPS L min -1 DDS L min -1 compressed air supply 2.3 L min -1 aerosol generation aerosol conditioning 2.7 L min -1 APS 3321 CPC A aerosol characterization 5.0 L min L min -1 Whole setup scheme for spray application, aerosol conditioning and characterization ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 17

18 Example: Nanostructured Particles which fulfil the EC recommendation on the definition of nanomaterials. 100 nm 2000 nm TEM-image of a synthetic and fractal SiO 2 -aggregat ( 500 nm) containing sintered nanoscale primary particles ( 18 nm) SEM-image of a dried spray droplet ( 5µm) made of acrylate topcoat with embedded TiO 2 pigment particles ( 200 nm) and embedded iron oxide nanoparticles (< 100 nm) ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 18

19 Standardizing: Particle measurement + Sample treatment process (+) Scenario (aging, weathering) (+) ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 19

20 Standardization/TC Structure ISO/TC 24/SC 4 Particle Characterization vertically, measurement methodology oriented ISO/TC 229 Nanotechnologies horizontally, interdisciplinary, application oriented CEN/TC 352 Nanotechnologies ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 20

21 Nanoparticles in Aerosols Standardization in nanoparticle characterization is performed in 15 Working Groups within ISO/TC 24/SC 4. Additionally to imaging methods for morphology inspection of single particles, aerosol measurement devices have some benefits for exposure analysis compared with particle measurement techniques for liquid dispersions (i.e. emulsions, suspensions or combinations of them), for instance the ability of providing absolute count numbers or the independency from specific material properties (e.g. from the index of refraction). A fundamental aerosol measurement principle that allows the characterization of particles down to a view nanometre is the electrical mobility analysis as described within ISO 15900:2009. One problem from metrological view, which still exists for aerosol measurement technology, is the lack of a concentration reference material. An important step in this direction represents the international standard draft (DIS) ISO/DIS 27891:2013 for the calibration of condensation counters. ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 21

22 Nanoparticles in Suspensions In the field of liquid dispersion characterization, a fundamental challenge is the characterization of the dispersion stability, i.e. the absence of change in specified properties over a given timescale. Therefore, the technical report ISO/TR 13097:2013 was issued by WG 16, which describes two different approaches to determine relative property changes. Especially in larger cluster research projects, dealing with fate, exposure and hazard of nanomaterials the sample preparation turned out to be the deciding step, e.g. for risk assessment of TiO2. Zeta potential measurement proved to be a necessary tool for checking dilution and stabilization protocols. Therefore, WG 17 issued methods for zeta potential determination within ISO 13099, which consists currently of two standards and one final draft of an ISO standard (FDIS). Respecting the preparation preconditions comparable and reproducible particle or agglomerate size measurement by centrifugal sedimentation or hydrodynamic mobility analysis (e.g. by dynamic light scattering - DLS) can be achieved. ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 22

23 ISO/TC 24/SC 4 Particle Characterization (16 P-Members, 12 O-Members, Liaison to ISO TC 229 and CEN TC 352) WG 1 "Representation of analysis data" WG 2 "Sedimentation, Classification" WG 3 "Pore Size distribution, porosity" WG 5 "Electrical sensing zone methods" WG 6 "Laser diffraction methods" WG 7 "Dynamic light scattering" WG 8 "Image Analysis methods" WG 9 "Single Particle light interaction methods" WG 10 "Small angle X-ray scattering" WG 11 "Sample preparation" WG 12 "Electrical mobility and number concentration analysis for aerosol particles" WG 14 "Acoustic methods" WG 15 "Focused scanning beam techniques" WG 16 Characterisation of particle dispersion in liquids WG 17 "Methods for zeta potential determination" ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 23

24 WG 12 Aerosol Measurement ISO 15900:2009 Determin. of particle size distribution Differential electrical mobility analysis for aerosol particles ISO/FDIS 27891:2014 Aerosol particle number concentration Calibration of condensation particle number counters optical detector condensation chamber Particle Concentration cm cm -3 1 cm -3 1 nm Aerosol Electrometer Condensation Particle Counter Optical Particle Counter 10 nm 100 nm 1000 nm Particle Size Concept of particle number concentration standard (detection efficiency determin.) ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 24

25 WG 17 Zeta Potential Measurement Nanoparticle Double Layer Interaction K. Schießl, F. Babick et al. Advanced Powder Technology 23 (2012) ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 25

26 CNT Composites - Scenarios Nowack et al.: Potential release scenarios for carbon nanotubes used in composites, Environment International 59 (2013) 1 11 ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 26

27 Results From characterisation of nanomaterial release during their lifecycle: - Particle size distribution and concentration alone are not sufficient - Sample amount related quantities (e.g. numbers) and also larger particle size ranges for plausibility balancing are necessary - Sample treatment processes can be more important than sample material - Matrix and nanoparticle embedding properties are important - Nanoparticle release from non-nanomaterials like polymer matrices ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 27

28 Conclusions For characterisation of nanomaterial release during their lifecycle: - Methodology is now available and subject of international standardization. - World wide community has test methods adopted and validation and ILC started. - Estimation of potential release (Precaution) on basis of TEM-images of prepared nano-object structures is not longer a sound scientific basis. (Apart from granulometric analyses by imaging methods (SEM, TEM), the metrological determination of characteristic properties allowing the classification of a material as a nanomaterial in accordance with the recommendation of the European Commission is still a complex scientific and technical challenge.) The measurement of aggregate/agglomerate size distributions under defined conditions (e.g. dispersing procedures, release scenarios) is essential for characterizing particulate systems. ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 28

29 Thank you! Attachments for further information: Nanosafetycluster ILSI NanoRelease Consumer Products NANOfutures ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 29

30 NanoSafetyCluster: Study 2013 Nanomaterials from release to exposure Kai Savolainen (coordinator), Ulrika Backman, Derk Brouwer, Bengt Fadeel, Teresa Fernandes, Thomas Kuhlbusch, Robert Landsiedel, Iseult Lynch, and Lea Pylkkänen: Nanosafety in Europe : Towards Safe and Sustainable Nanomaterials and Nanotechnology Innovations Finnish Institute of Occupational Health, ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 30

31 NanoSafetyCluster Study 2013 General processes and areas of possible release and exposure: 1. Production Possible release during production may occur through leaks into water and air in closed systems or open production processes. (NANOSH,CarboSafe, nanogem) 2. Handling and use Handling and use covers several process-related stages e.g. handling of powders, diffuse emission from production plants, mechanical treatment of nanomaterials 3. Aging Aging encompasses all processes taking place in the environment such as selective degradation, wash-out, increased brittleness of the material ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 31

32 NanoSafetyCluster Study 2013 General processes and areas of possible release and exposure: 4. End of Life (EoL) End of Life activities refer to activities related to i) re-use or recycling; ii) waste treatment, and iii) disposal. In particular, during high energy processes, the release of nano-objects may not be excluded. The required research priorities on exposure, transportation and life cycle include: - Mechanistic understanding of processes determining the release of ENM. - Understanding the transformation and transport of ENM. - Understanding workplace, consumer and environmental exposure. ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 32

33 Actually: Spread into Worldwide Community ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 33

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37 Life Cycle of Nanomaterials Standards needed Standards for material characterisation Standards for commercial specifications for trading Standards for safety testing e.g. of cosmetics Cross-ETP Coordination Initiative on nanotechnology MATERIALS MODELLING & DESIGN TOOLS COMPONENTS ASSEMBLERS (Products & Services) END-USERS (customers, public) END OF LIFE METROLOGY Standards for QSARs & modelling techniques Standards for measurement methods Standards for exposure assessment and safe handling Standards for waste handling & treatment General Value Chain: Mapping for Standards Courtesy of Rob Aitken, Key Node Leader: Safety and Sustainability NANOfutures ( Value4Nano ): WG Standardization WG-Chairs: Michael Stintz, Daniel Bernard, Gianfranco Coletti Safety & Sustainability Key Node ECHA Workshop M. Stintz: Characterisation of nanomaterial release during their lifecycle 37