Rodney Weber, Qian Zhang, Jenny Wong

School of Earth and Atmospheric Sciences, Georgia Institute of

Technology; Atlanta, GA/USA

Aika Davis , Marilyn Black

Underwriters Laboratories Inc.; Marietta, GA/USA

Fine particulate and chemical emissions from desktop 3D printers

Printing for Fabrication 2016

Manchester, Sept. 14

1

Outline • Approach

• Results

– Particle Number emissions, (Surface Area and Mass)

– Particle chemical composition

– Toxicity

– VOCs

• Summary

MotivationConsumer 3D printers are used in environments where exposures to unknown emissions can occur. Exposures include susceptible populations.

ObjectiveDevelop standard method for characterizing consumer 3D printer emissions; assess emissions and parameters affecting emissions.

2

Overall Approach

Standardized testing method to understand emissions

Similar to testing laser printer emissions

Work Spaces, Classrooms, Library's, etc.

Apply results to determine exposure in

various settings

Primary School

Exposure Assessment

Focus of this talk3

1 m3

chamber

Filter or Mass Spec

TSI CPC3022

TSI AeroTrak9306-01

TSI SMPS DMA(3080)

Water CPC (3785)

Clean, dry, room air (filtered, VOC denuded)

Chemical Analysis Fine particle sizedistribution

Fine particle sizedistribution

Total numberconcentration*

300 nm - 25 μm 7 – 300 nm >7 nm

Experimental system for characterizing emissions: Run printer in controlled setting, chamber

VOC and Aldehyde Sampling,Offline analysis

Temp: 24℃ RH: 3%Open exhaust

VOCs

Particle Composition, Total Particle Number and Number vs size for 7nm to 25 µm4

1 m3 StainlessSteel Chamber

Well mixed

Air exchange rate = 1 hr

Method: Calculating particle emissions from printer

5

Blue Angel Test Method for Laser Printers

Test method for the determination of emissions from hardcopy devices; Blue Angel Ecolabel for Equipment with printing function according to RAL-UZ-171

Measurements made before, during and after printing to determine:

PER(t) =VCCP (t)-CP (t - Dt)exp(-b ×Dt)

Dt exp(-b ×Dt)

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PER(t): Particle emission rate, s-1

TP =VCDCP

tstop - tstart+ b ×Cav

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ö

ø÷÷ tstop - tstart( )

TP: Total particle number emitted, #wall losses from exp decay

Eg, laser printer particle concentrations

Similar for surface area and mass emissions

6

3D Printer Particle Number Emissions: Short vs long print time, ABS filaments

~7 hr Print time~1 hr Print time

Number, Surface Area and Mass

• Significant emission in number, surface area and mass• Large initial peak due to new New Particle Formation (NPF) of printer-emitted

semi-volatile vapors.

Start

NPF

7

3D Printer Particle Emissions: Size distribution evolution with printing time (ABS filament)

Particlesgenerated fromvapor nucleationand grow by condensation andcoagulation

nanoparticles

Number

Surface Area

Mass

time

dS/d

logD

p,n

m2/cm

3

NPF

Testing factors affecting particle emissions

Tested emissions as a function of:1. Nozzle temperature

2. Filament material• ABS, PLA, Nylon

3. Filament color• yellow, blue, green, red, white

4. Filament brand• 6 different brands

5. Printer brand• 3 different printers, open and enclosed

6. Etc. Over 190 test runs.

8

Nozzle TemperatureConsistent with vapors particles

Yield = Total Emission (TP) per mass of filament consumed

Higher T more VOC emissionsExp more particles formed

ABS filament

3D Printer Particle Number Emissions: Filament type

One brand of ABS filament produced many more particles (super emitter) Summary of other published

work (Azimi et al., 2016; Kim et al., 2015; Stabile et al., 2016; Steinle, 2016; Yi et al., 2016)

Total number of particles emitted (TP) per mass of filament used

10

ABS

ABS

3D Printer Particle Number Emissions: Differing filaments vs Laser Printer emissions

Maximum Number Concentrations During Printing

Average Number Emission Rate (PER) During Printing

3D Printers 3D PrintersLaser Printers Laser Printers

11Laser printer emissions are based on published studies

3D Printer Particle Emissions: What is happening

Filament

T

Source of vapors from heated bed Aerosol dynamic model under development

Feed rate

1. Semivolatile compounds emitted near extruder nozzle: f(T)

2. Vapors: -Nucleate to form new particles-Condense on existing particles

3. Particles-particle coagulation

4. Dispersion/dilution into chamber

5. Wall losses

12

3D Printer Particle Emissions: Chemical composition of particles vs bulk filament

Online Mass Spec. measurement of just particle composition

PLA-generated particles mass spectra similar to monomers of filament, ABS particles differ from monomers

Pyrolysis GC MS analysis of filament and particles collected on a quartz filter

ABS-generated particles different composition than filament. Particles composed of additives and some fatty acids

13

Preliminary particle toxicity tests, acellular and cellular assay testing for oxidative stress

Super-emitting filament ABS brand

Collect 3D printer particles on teflon filter, extract to obtain particles in aqueous samples (colloid), analyze toxicity

Acellular assay, Dithiothreitol (DTT): Ability of particles to generate ROS (Reactive Oxygen Species).

Mice intratracheal installation: Broncho-alveolar lung fluid total cell count after 24 hrs, a measure of inflammatory reaction.

Super emitting ABS filaments similar toxicity to regular ABS emitting filaments. PLA generated particles more toxic than ABS

Similar results

3D Printer VOC Emissions

52%

23%

13%

5%2%

1%

1%

3%

PLA

Methyl methacrylate

1-Butanol

Lactide

1-Dodecanol

Acetaldehyde

Cyclotetrasiloxane,octamethyl î-Caprolactam

98%

1%1%

Nylon

î-Caprolactam

Lactide

1-Hexanol, 2-ethyl

Nonyl aldehyde

Acetaldehyde

other

68%

8%

3%

2%

3%

2%

1% 13%

ABSStyrene

Benzene, ethyl

Methylene chloride

Acetaldehyde

Vinyl cyclohexene

Benzaldehyde

Caprolactam

Other

Styrene: probable carcinogen, Effects: odor, eye & respiratory system, reproductive/development, nervous system

Styrene

Caprolactam

Me

thyl

met

hac

ryla

te

Caprolactam Effects: eye, skin, respiratory, cardiovascular,

central nervous systems, liver, kidney

Methyl Methacrylate Effects: odor, eyes, skin, and respiratory system

PLA

Nylon

ABS

14

Summary1. Consumer 3D printers can emit substantial levels of non-engineered

nanoparticles and VOCs. Exposures will depend on operating environment.

2. Significant variability in particle emissions as a function of:• Filament material: large effect (ABS ~ nylon > PLA, related to nozzle T)

• Filament brand: large variability (super emitting brand of ABS, unknown additives?)

• Filament color: generally smaller effect

• Printer brand (depends mainly on nozzle T), some effect of enclosures.

• Bed heating, little increase in number, increases surface area and mass concentrations.

3. Chemical composition of emitted ABS particles differs from bulk filament, PLA particle is similar to bulk.• Implications for particle toxicity.

• Preliminary results: acellular & cellular assay are consistent; PLA more toxic the ABS (OS)

• Additional chemical analysis and toxicity is on-going

4. VOCs of known health risks are emitted.15

16

Funding provided by Underwriters Laboratories Inc.,

A Not For Profit Organization dedicated to research, outreach and education for advancing public safety.

Summary

5. Manufactures of printers and filaments can consider ways to reduce emissions:• Lowest nozzle T as possible• Active emission reduction (enclosures with VOC scrubbers/filters)• Type of filament and additives

Parking lot

Experimental System (UL chamber)

18

1 m3 chamber

Chamber

Inside chamber

Clean air delivery system

Acrylonitrile Butadiene Styrene (ABS): Filament vs particles

acrylonitrile*

19

1,3-butadiene* styrene*

MS of Particle Emitted

Emitted particles may to have a different composition than monomers of filament

*spectra from NIST webbook

Polylactic Acid (PLA): Filament vs particles

20

lactic acid* lactide*

Emitted particles are mostly similar in composition to monomers of filament

MS of Particle Emitted

*spectra from NIST webbook

Health Implications: VOC

ABS• Styrene: probable carcinogen, odor, eye & respiratory system, reproductive/development, nervous system

• Ethylbenzene: probable carcinogen, odor, liver, kidney, endocrine systems, development

• Methylene Chloride: probable carcinogen, odor, cardiovascular & nervous systems

• Acetaldehyde: probable carcinogen, odor, eye & respiratory systems

• Vinyl cyclohexene: probable carcinogen, reproductive & respiratory systems

PLA• Methyl Methacrylate: odor, eyes, skin, and respiratory system

• 1-Butanol: odor, eyes, skin, respiratory system, central nervous system

• Acetaldehyde: probable carcinogen, odor, eye & respiratory systems

Nylon• Caprolactam: eye, skin, respiratory, cardiovascular, central nervous systems, liver, kidney

• Acetaldehyde: probable carcinogen, odor, eye & respiratory systems

Comparison of Py GCMS Results #1

22

Raw Filament

5.00 10.00 15.00 20.00 25.00 30.0002000000400000060000008000000

1e+071.2e+071.4e+071.6e+071.8e+07

2e+072.2e+072.4e+07

Time-->

AbundanceTIC: ABS-Red-EGA01.D\data.ms

5.00 10.00 15.00 20.00 25.00 30.0002000000400000060000008000000

1e+071.2e+071.4e+071.6e+071.8e+07

2e+072.2e+072.4e+07

Time-->

AbundanceTIC: Sample#2-EGA01.D\data.ms

Raw Filament

Particle Collection

ABS polymer fragment

No ABS polymer fragment

5.00 10.00 15.00 20.00 25.00 30.00100000020000003000000400000050000006000000700000080000009000000

1e+07

Time-->

AbundanceTIC: ABS-DS01A.D\data.ms

5.00 10.00 15.00 20.00 25.00 30.00100000020000003000000400000050000006000000700000080000009000000

1e+07

Time-->

AbundanceTIC: SAMPLE2-DS01A.D\data.ms

1

2 34 5

67

8

911

10

1345

6 7 910

12

Raw Filament

Particle Collection

23

# Compound name Structure Description

1 2-Naphthalenecarbonitrile

2 n-Hexadecanoicacid

C16H32O2

3,

4,

5,

6,

7,

Isomer of 2-[1-(4-Cyano-1,2,3,4-tetrahydronaphthyl)]propanenitrile

C14H14N2

8 Octadecanoic acid

C18H32O2

9,

10uknow

11 Irganox 1076(Ciba-Geigy)

12 unknow

Comparison of Py GCMS Results #2

Summary

24

The polymer species of Raw filament were identified as ABS. Particle sample doesn’t show the fragment of ABS species.

The major composition of particles were the collection of additives from raw filament and some fatty acid.

25

3D Printer Particle Number Emissions: ABS filament

• Significant emission in number, surface area and mass• Large initial peak due to new particle formation by homogeneous nucleation

of printer-emitted vapors (seen in many studies).

Log Scale Linear Scale

Nucleation