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Characterization of Mechanical and UV-Induced Nanoparticle Release from Commercial Products Lipiin Sung 1 , Keana Scott 2 & Treye Thomas 3 1 Engineering Laboratory, NIST, Gaithersburg, MD 2 Material Measurement Laboratory, NIST, Gaithersburg, MD 3 Office of Hazard Identification and Reduction, CPSC, Rockville, MD QEEN Workshop 2015 July 7 th , 2015 Arlington, VA

Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

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Page 1: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Characterization of Mechanical and UV-Induced Nanoparticle Release from Commercial Products

Lipiin Sung1, Keana Scott2 & Treye Thomas3

1Engineering Laboratory, NIST, Gaithersburg, MD 2Material Measurement Laboratory, NIST, Gaithersburg, MD 3Office of Hazard Identification and Reduction, CPSC, Rockville, MD

QEEN Workshop 2015 July 7th, 2015 Arlington, VA

Page 2: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Acknowledgements

MML (Materials) EL (Engineering) ITL (Information Science) CNST (NanoFab) PML (Physics)

2

NIST Disclaimer Certain commercial equipment, instruments, or materials are identified in this talk to foster understanding. Such identification does not imply recommendation or endorsement by NIST, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.

CPSC Disclaimer This project was funded by the U.S. Consumer Product Safety Commission (CPSC). The content of this publication has not been reviewed or approved by and does not necessarily reflect the views of the Commission, nor does mention of trade names, commercial products, or organizations imply endorsement by the Commission

Page 3: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Nano Release at NIST

• NIST-CPSC Projects • MWCNT, metal oxide & inorganic nanoparticle

release from commercial products • Nanomaterial release from fire retardant products

• NIST Projects • MWCNT release from composite materials • MWCNT release visualization • Impact of weathering on nanoparticle release from

composite materials

3

Page 4: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Mechanically induced MWCNT release from nanocomposites • Characterization of intact nanocomposite

materials • Raman, SEM & TEM • Commercial materials often have carbon fibers as well as

MWCNTs – additional analytical challenges

• Mechanical release - cutting, sawing, abrasion • Released particle collection and analysis

• Passive collection, MOUDI, electrostatic precipitator, filtering • Real-time particle analysis – CPC, SMPS • Release particle analysis – Raman, SEM/STEM, LM

4

Page 5: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Passive sample collection from sawing and cutting

• Mostly µm- to mm-sized particles consisting fiber bundles, resin pieces, paint chips, etc.

• Might contain bare or small clusters of nanoparticles.

Low resolution

mode

High resolution

mode

Page 6: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Aerosol sampling challenges

6

Loss during aerosol collection • Flow rate • Collection substrate efficiency • Total collection efficiency

Loss or contamination from sampling chamber • Contaminants from abrading tip, sample

holder, etc. • Position of intake port • Speed of inlet air/chamber air flow • Net positive or negative flow

Loss during realtime analysis • Flow rate • Charge neutralization • Analytical speed

Loss during transport • Tube type, length, size • Flow geometry • Mismatched flow velocity

?

Page 7: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Nanoparticles from cutting debris • What do we mean by released MWCNT?

• Partially embedded • Attached • Loose

• Are rod shaped particles MWCNTs?

• What about other nano-sized particles?

500 nm 200 nm 500 nm

Page 8: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

10 nm 200 nm

Page 9: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

STEM in SEM • STEM in SEM can provide

MWCNT distribution and size information.

• Easier, faster and cheaper than dedicated TEM investigation.

• Cannot visualize the wall structure in epoxy matrix (but it can do it with free-standing CNTs).

3 µm

500 nm

Page 10: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Size separated sampling helps but …

• Relatively high resolution (30 nm x 30 nm pixel) imaging is needed to located individual CNT particles

• Manual survey is not realistic.

3 mm

Total sampling area

3 m

m

2k x 2k image with 30 nm pixel

60 µm

60 µ

m 2500 images needed to

cover the sampling area fully!

35+ GB of images

10

Bare MWCNTs on Si

Page 11: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Automated SEM imaging

1 mm

25 m

m

11

1” MOUDI substrate

Page 12: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Challenges for nanorelease characterization • Better process control for particle sampling

• Loss through diffusion? • Setup (tube length, inlet location, flow rate, collection

substrate, etc.) dependent variations • Effective size separated sampling

• Automated and faster imaging and analysis process • Very small objects (nano) in a large field of view (statistics)

• Data management must be part of the solution

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Quantitative analysis of release may be difficult until experimental processes are fully

characterized

Page 13: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Model Epoxy (EP) MWCNT SiO2

Release Pathways of Nanoparticles (NP) During the Life Cycle of Nanocomposites: Mechanical, Matrix Degradation, Chemical Dissolution, Fire/Incineration, etc.

Mechanical abrasion# Matrix Degradation via UV

Polyurethane (PU) flooring coatings on wood substrates

SiO2 Al2O3

Latex Coatings on a dry-wall substrate

TiO2 ZnO Ag

Exterior Coatings and Paints SiO2-PU ZnO -Latex

*Abrasion after UV exposure

# Airborne release particles- working with Indoor Air Quality Group/EL

Goal: • To develop test methods and measurement protocols for determining the quantities

and properties of nanoparticles released from polymer nanocomposites • To understand the mechanism that causes nanoparticles to leave the polymer matrix

during exposures to the environments Providing data needed for assessing and managing potential EHS risks of NP release during nanocomposites’ life cycles. 13

Page 14: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Speed # of cycles Load Type of wheels

Matrix Degradation via UV Mechanical abrasion Taber rotary abraser

(ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput,

High Intensity UV Chamber

1. Characterize abraded surfaces (LSCM, SEM, EDX)

2. Remove Particles from Abraded Surface (TEM grid pressed against the surface or using an Adhesive Tape)

3. Collect residues from abrasion wheels

2 & 3 Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), SEM/EDX

UV intensity Temperature Humidity

To be analyzed by ICP-OES

Simulated Rain Test (Water Spraying)

14

Page 15: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

• Commercial rotary abraser can be used for nanoparticle release study, but commercial

abrading wheels that are composed of a polymer binder and inorganic abrasives release their own particles not suitable

tungsten wheel

CS-10 wheel CS-17 wheel S-35 wheel (Metal)

large grooves

Fewer particles

150 µm x 150 µm

• NIST-made deep cross-patch (MW2) or sandblasted (MW4) noncorrosive stainless steel (e.g., 316 SS) wheels having a root mean square (RMS) surface roughness between 5 µm and 7 µm, are suitable for reproducibly abrading in water and in air for coatings and paints containing nanoparticles.

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Page 16: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

• Laser scanning confocal microscopy (LSCM) in combination with image analysis is a good, relatively fast method for quantifying the number and size distribution of release metal-oxide/inorganic particles accumulated on abraded surfaces having particle size greater than 100 nm (detection limit).

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

20

40

60

80

100

120

140

160

180

Total:326 ± 12%

1

Cou

nt

size (µm)

94

141

63

166 2

72 rpm500 cycles1000g

LSCM can be used as a screening tool for a quick detection

Released forms? nanoparticle clusters or nanoparticles embedded in polymer matrix?

To identify the particles on surface SEM/EDX, ICP-OES SEM images: particles from Abraded Surfaces (TEM grid pressed against the surface)

Al2O3

TiO2

ZnO

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Page 17: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Neat PU and 5 % (by mass) nanosilica in PU (commercial, containing UV absorbers)

Nanosilica (surface treated) in suspension Exposed on NIST SPHERE at 50 °C and both dry (0%RH) and

humid (75% RH) conditions (PU: Tg = 40.4 ± 3°C)

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Characterization • Chemical Degradation (rates, mechanism)- FTIR, UV-vis, and XPS • Surface Morphologies (AFM, SEM, EDXS) • Release: amount & rate by ICP-OES

Release Pathways: Polymer matrix degradation via UV exposure Simulated rain test Abrasion test

Page 18: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Speed # of cycles Load Type of wheels

Matrix Degradation via UV Mechanical abrasion Taber rotary abraser

(ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput,

High Intensity UV Chamber

UV intensity Temperature Humidity

Abrasion parameters: MW2 metallic wheels Fixed loading 100 cycles

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To be analyzed by ICP-OES

Simulated Rain Test (Water Spraying)

Page 19: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

FTIR – Intensity Mass loss

Rates of chemical degradation and weathering-induced mass loss of commercial PU nanocoating (ENC) were lower than those of the neat PU, indicating that surface-treated silica nanoparticles had photostabilized the PU matrix.

ENC: SiO2-PU 19

Page 20: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

20 µm scan

1 µm scan

Hight

Hight

Phase

Phase

0 d

26 d

AFM SEM/EDX

Silica nanoparticles were observed to accumulate and cluster on the nanocoating surface with increasing UV exposure time and eventually release from the nanocoating.

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Page 21: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

0

1

2

3

4

5

6

0 20 40 60 80 100 120

Rele

ased

Si M

ass

(µg)

Exposure Time (days)

Total Si collected:16.9 µg ± 0.5 µg PU: 2.8 mg/m2 ± 0.1 mg/m2 after 103 days Model epoxy: 83.1 mg/m2 ± 0.2 mg/m2 after 72 days

Two increases at 14 days and 87 days

Humidity inside the cell~ 75% RH

14 days

Savelas Rabb & Lee Yu, MML/NIST

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Page 22: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

Surface morphology & mass loss before and after abrasion 50 °C and dry (0%RH)

Exposure days 0 10 20 40 60

Mbefore abrasion-Mafter abrasion (mg)/samples

0.15 ± 0.10

0.73 ± 0.39

2.20 ± 0.27

1.82 ± 0.52

1.98 ± 0.17

Mass of Si (µg) by ICP* 2.2 ± 1.4

2.01 ± 0.51

1.92 ± 0.50

0 10 20 30 40 50 600.0

0.5

1.0

1.5

2.0

2.5

3.0

Mas

s Lo

ss (m

g)

Exposure Time (d)

* Collected from abrasion wheels

Mbefore abrasion-Mafter abrasion (mg) averaged of 6 samples

averaged of 4 samples

Before

After

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Page 23: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

0.0 0.2 0.4 0.6 0.8 1.00

10000

20000

30000

40000

50000

Tota

l Sur

face

Par

ticle

Cou

nt (1

/mm

2 )

Particle Size (µm)0.0 0.2 0.4 0.6 0.8 1.0

10000

20000

30000

40000

50000

Tota

l Sur

face

Par

ticle

Cou

nt (1

/mm

2 )

Particle Size (µm)0.0 0.2 0.4 0.6 0.8 1.0

0

10000

20000

30000

40000

50000

Tota

l Sur

face

Par

ticle

Cou

nt (1

/mm

2 )

Particle size (µm)

0.0 0.2 0.4 0.6 0.8 1.00

10000

20000

30000

40000

50000

Tota

l Sur

face

Par

ticle

Cou

nt (1

/mm

2 )

Particle Size (µm)

0 d

40 d

20 d 10 d

60 d

0 20 40 600

20000

40000

60000

80000

100000

120000

Tota

l sur

face

par

ticle

cou

nt (1

/mm

2 )Exposure time (d)

0.0 0.2 0.4 0.6 0.8 1.00

10000

20000

30000

40000

50000

Tota

l sur

face

par

ticle

cou

nt (1

/mm

2 )

Particle size (µm)

Surface morphology after abrasion – at different UV exposure times

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Page 24: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

The trends (as a function of exposure time) of released Si mass collected from simulated rain process and the mass loss & total surface particle counts from abrasion process are similar.

0

0.5

1

1.5

2

2.5

3

0 10 20 30 40 50 60 70

Rele

ased

Si M

ass

(µg)

Exposure Time (days)

Simulated rain process

0 20 40 600

20000

40000

60000

80000

100000

120000

Tota

l sur

face

par

ticle

cou

nt (1

/mm

2 )

Exposure time (d)

Abrasion process

Silica nanoparticles were observed to accumulate and cluster on the nanocoating surface with increasing UV exposure time and eventually release from the nanocoating.

0 10 20 30 40 50 600.0

0.5

1.0

1.5

2.0

2.5

3.0

Mas

s Lo

ss (m

g)

Exposure Time (d)

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Page 25: Characterization of Mechanical and UV-Induced Nanoparticle ... · Taber rotary abraser (ASTM D 4060-14, organic coatings) NIST SPHERE High Throughput, High Intensity UV Chamber

• How to capture released particles?

• Evidence of particle release – detection? Can you detect discrete nanoparticles? High resolution microscopy –SEM/TEM –labor intensive ICP – element analyses Others

• The size and form of released particles? Size: range from “nano” to “micro” depends on release mechanism Form: free nanoparticle? nanoparticles embedded in polymer matrix? Can we distinguish between agglomerates and aggregates of nanoparticles?

• What are the best methods available to answer these questions? Reference?

• Experimental data are needed for assessing and managing potential EHS risks of nanoparticles release during nanocomposites’ life cycles.

• Need guidelines and protocols!

Concern: Harmful effects of surface-exposure and release of nanomaterials during the life cycle of polymer nanocomposites?

25