Acrylic Tests

• These slides show the tests that are currently being done or are planned to be done on acrylic to determine some of it’s properties under different conditions.

• These tests will be useful in minimizing systematic errors in the detectors from the acrylic vessels.

Wet Acrylic Behavior

• We’re soaking acrylic samples in Distilled Water, Mineral Oil, and LAB.– Simulates Filled AVs– We’re measuring their weights and dimensions to see how they

increase with time.– We’re also measuring the transmittance of the acrylic pieces to

see how it changes as the different liquids are absorbed

• This is currently being done in the lab.

Data From Soaked Acrylic SamplesAcrylic submerged in different liquids

97.898

98.298.498.698.8

9999.299.499.6

0 10 20 30 40 50 60

Days Submerged

Wei

gh

t(g

) LAB

DI Water

Mineral Oil

• These three samples had relatively the same weight and were each submerged in a different liquid.– The sample’s weight in Distilled Water has increased ~ .4%– The sample’s weight in Mineral Oil has increased ~ 1.6E-2%– The sample’s weight in LAB has stayed relatively the same

• The other 2 samples that were in each liquid showed similar changes in weight.

• These three samples had relatively the same length and were each submerged in a different liquid.– The sample’s length in Distilled Water has increased ~ 4E-2%– The sample’s length in LAB and Mineral Oil has stayed relatively the

same.• The other 2 samples that were in each liquid showed similar

changes in length.• The other dimensions of the acrylic samples have stayed about the

same since they are so much smaller than the sample’s length.

Acrylic Submerged in Different Liquids

3.0788

3.0792

3.0796

3.08

3.0804

3.0808

3.0812

0 10 20 30 40 50

Days Submerged

Len

gth

(in

)

LAB

DI Water

Mineral Oil

Sample soaked in LAB

0

20

40

60

80

100

0 200 400 600 800 1000

Wavelength(nm)

% T

ran

smit

tan

ce

Day 0

Day 58

• This graph shows the percent transmittance from a piece of acrylic before it was submerged in LAB and after 58 days absorbing LAB.

• The percent transmittance has stayed relatively constant for all wavelengths

• The other two acrylic pieces in LAB have shown similar properties.

Sample soaked in DI Water

0

20

40

60

80

100

0 200 400 600 800 1000

Wavelength(nm)

% T

ran

sm

itta

nc

e

Day 0

Day 58

• This graph shows the percent transmittance from a piece of acrylic before it was submerged in DI water and after 58 days absorbing DI water.

• The percent transmittance has slightly decreased for wavelengths around 300-600nm.

• The other two acrylic pieces in DI water have shown similar properties.

Sample soaked in Mineral Oil

0

20

40

60

80

100

0 200 400 600 800 1000

Wavelength(nm)

% T

ran

smit

tan

ce

Day 0

Day 58

• This graph shows the percent transmittance from a piece of acrylic before it was submerged in Mineral Oil and after 58 days absorbing Mineral Oil.

• The percent transmittance has decreased for nearly all wavelengths but it has substantially decreased for wavelengths between 300 and 600nm.

• The other two acrylic pieces in Mineral Oil have shown similar properties.

Dry Acrylic Behavior

• After we’ve let the samples soak for an ample amount of time we are going to dry them out.– Measure weights and dimensions as they dry out to see how fast

samples will revert back to original state

• We will also work on an extreme dry-out of acrylic:– Environment:

• In Abbess vaccuum chamber at atmospheric pressure• Supplied gas in chamber will be boil-off from LN dewar• Simulates AV environment between assembly and filling

– Submit production acrylic coupons to this dry environment– Weigh samples every so often– Submit both dry and non-dry samples to stress tests, to check

for changes in stress properties of dry acrylic.

Acrylic Coupons

Samples should be annealed after machining to remove residual stresses.An oven must be purchased for this purpose.

Acrylic sample

We can stress the acrylic samples to 5MPa to see if crazing will occur

Procedure follows ASTM D6272

Stressing Procedure

Stressing Acrylic Coupons

Stainless rod; serves as stressing weight

These rods keep weight rods at fixed distance

Weight rests on these aluminum rods

These rods keep base rods at fixed distance

Acrylic rests on these base rods

Stressing in Dry EnvironmentProcedure follows ASTM D6272

LN Boil-off

Exhaust

Acrylic Outgassing

• We will test the outgassing and diffusion of air through acrylic:– Pull vaccuum on our container while an aluminum lid is on– Turn off vacuum pump– Monitor loss of passive vaccum with vacuum gauge

• Repeat process with an acrylic lid• Difference in vacuum loss gives out-gassing rate

Freon Compatibility

• Repeat dry acrylic setup, but with freon gas– Check transmittance, stress characteristics of acrylic coupons

during/after exposure to freon

• Can also check outgassing of freon:– Outgas acrylic sample in vacuum chamber– Fill chamber with freon to re-gas acrylic with freon– Pull vacuum again, and see how quickly vacuum loss is different

with and without freon-gassed acrylic sample.

This hose will connect the vacuum chamber to a bottle filled with Freon

The other vacuum valve will be opened to allow the Freon to cycle in through the chamber

Temperature Cycling of Acrylic• We will place the acrylic samples in a programmable

convection oven to cycle the temperatures. Then we will observe the transmittance and stress properties of these samples.

• Heating cycles can mimic:– AV shipping procedure– Annealing cycles at Reynolds

• An oven needs to be purchased for this purpose.

• Shouldn’t need to put vacuum chamber inside oven, so oven can be small and does not need gas feedthroughs

• http://www.mcmaster.com/#laboratory-ovens/=a24d0d

Acrylic samples stressed in oven

Low-temperature Acrylic

• We will place the acrylic samples in a low temperature environment, like a freezer, and observe the changes in transmissivity and stress properties.

• We can worry about this later; we have plenty on our plate that is much more germane to Daya Bay.

Conclusion

• The tests that are currently happening have given some interesting results, but they have to be continued before any conclusions can be drawn from them.

• The other tests will be completed in order to avoid systematic errors in the detectors from the acrylic vessels.

References

• “Standard Test Method for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials by Four-Point Bending”