Within-Chamber Uniformity of Xenon Test Chambers

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1 Within-Chamber Uniformity of Xenon Test Chambers Revolving Drum & Static Array Specimen Mounting Systems Presented by Jeffrey Quill, Director of Technical Applications, Q-Lab

2 The Perfect Tester Would Produce uniform irradiance, temperature, and humidity throughout the chamber

3 It is NOT possible to produce perfect uniformity

4 Purpose Focus on the uniformity of degradation of test specimens Revolving drum Static array

5 Cooperating Labs A total of six laboratories participated in the study 3 coatings manufacturers (A2LA) 2 independent testing labs (A2LA) 1 equipment manufacturer (A2LA) All six labs have many years of experience with xenon arc testing.

6 Test Equipment Xenon Testers Used In Study Rotating Drum Ci5000 Ci4000 Ci65A Static Array Q-Sun Xe-3-HS

7 Test Equipment Xenon Chamber Types Rotating Drum lamp in the center and a cylindrical specimen mounting rack around the lamp which rotates the test specimens Xenon Lamp Black Panel Light Monitor Specimen Rack Specimen Spray Back Spray

8 Test Equipment Rotating Drum First introduced in tier racks introduced in 1980 s improve uniformity Monitors and controls irradiance, black panel temperature, chamber air temperature, and relative humidity

9 Test Equipment Xenon Chamber Types Static Array Filter Water Spray Nozzle Xenon Lamp Lamps placed above a static, flat plane specimen tray Test Specimen Irradiance Sensor Black Panel

10 Test Equipment Static-Array Reflective chamber walls and lamp housings maximize irradiance uniformity Monitors and controls irradiance, black panel temperature, chamber air temperature, and relative humidity

11 Test Procedure Multiple replicates used to map uniformity of chamber Between 9 and 108 replicates used, depending on chamber size and test cost

12 Test Procedure Test Materials Standard reference materials chosen Well understood environmental susceptibility Well understood modes of degradation

13 Test Procedure Test Materials Polystyrene Blue Wool AATCC L2 AATCC L4 Automotive Alkyd Melamine

14 Test Procedure Test Materials Standard Reference Materials Different material types Failure modes Sensitive to different factors

15 Test Procedure Test Materials Polystyrene: Clear plastic lightfastness standard SAE J1960 and J1885 Mode of degradation is yellowing Sensitive to temp. & Irradiance Specimen size was 50mm x 75mm x 3mm

16 Test Procedure Test Materials AATCC Blue Wool L2: Blue dyed wool lightfastness standard AATCC test method 16 Mode of degradation is fading Sensitive to temperature, relative humidity, and irradiance Specimen size was 50mm x 100mm

17 Test Procedure Test Materials AATCC Blue Wool L4: Similar to L2 except darker & more stable Fades at about 1/4 the rate of L2 Specimen size was 50mm x 100mm

18 Test Procedure Test Materials Automotive Alkyd-Melamine: Automotive reference material VDA TM Mode of degradation is cracking Sensitive to temperature, irradiance, and time of wetness Specimen size was 75mm x 75mm x 0.8mm

19 Test Procedure Specimen Mounting Mounted specimens properly As defined by equipment manufactures As defined by test methods Improper mounting can lead to inaccurate and misleading results

20 Test Procedure Specimen Mounting Polystyrene and automotive Alkyd Melamine mounted without backing Blue wool mounted with white card stock backing AATCC test method 16

21 Test Procedure Rotating-Drum Specimen Mounting 3 holders with 3 specimens each 1 on top tier 1 on middle tier 1 on bottom tier

22 Test Procedure Rotating-Drum Specimen Mounting Where more than 9 replicates were used, additional replicates were mounted in positions around the drum

23 Test Procedure Rotating-Drum Specimen Rotation Specimens are repositioned automatically in one dimension horizontally around the lamp Xenon Lamp Black Panel Light Monitor Specimen Rack Specimen Spray Back Spray

24 Test Procedure Rotating-Drum Specimen Rotation Xenon Lamp Black Panel Light Monitor Specimen Rack Specimen Spray Back Spray DOES NOT, however, compensate for variations in irradiance, temperature, and humidity in the vertical direction

25 Test Procedure Static-Array Specimen Reposition For tests that used repositioning: Specimens repositioned once a day as shown

26 Test Procedure There are, many other repositioning methods possible.

27 Test Procedure Exposure Conditions All machines configured to properly perform test methods used Proper optical filters used & light sensors Accurate calibration before testing started

28 Test Procedure Exposure Conditions SAE J2527 for Automotive Exterior step Time (hours: min) Lamp (on/off) Irradiance Black Panel Temp. (ºC) Chamber Air Temp. (ºC) Relative Humidity (%) Water Spray (on/off) 1 0:40 on off 2 0:20 on on 3 1:00 on off 4 1:00 off n/a on Extended UV Filters (QB) 0.55 w/m nm

29 Test Procedure Exposure Conditions SAE J2412 for Auto Interior step Time (hours: min) Lamp (on/off) Irradiance Black Panel Temp. (ºC) Chamber Air Temp. (ºC) Relative Humidity (%) Water Spray (on/off) 1 3:48 on off 2 1:00 -NAoff off Extended UV Filters (QB) 0.55 w/m nm

30 Test Procedure Exposure Conditions AATCC TM16 for Indoor Textiles step Time (hours: min) Lamp (on/off) Irradiance Black Panel Temp. (ºC) Chamber Air Temp. (ºC) Relative Humidity (%) Water Spray (on/off) 1 24:00 on off Window Glass Filters (B/SL) 1.10 w/m nm

31 Test Procedure Exposure Time Exposure depended on material Blue Wool L2 (20 hours) Automotive Alkyd-Melamine (up to 500 hours)

32 Degradation Measurements Evaluation As defined by test method used Ensure proper use of standard reference material Ensured accurate results

33 Degradation Measurements Color Measurements Blue Wool & Polystyrene Initial and final color measurements Delta b* used for polystyrene Delta E* used for blue wool

34 Degradation Measurements Color Measurements Blue Wool & Polystyrene Integrating sphere spectrophotometer Reflectance CIELAB color scale D65 illuminant 10º observer Large area view Specular component included UV component included

35 Degradation Measurements Cracking Measurements Automotive Alkyd-Melamine Inspected for cracking daily 10 cracks = FAILURE Time to failure

36 Test Summary Test Results 23 different tests performed Certain combinations repeated to determine repeatability

37 Test Summary Uniformity Uniformity is expressed as: ± two times the coefficient of variation (CV). The coefficient of variation is the standard deviation (s) divided by the mean (x). N =Number of Specimens X i =1st Data Point

38 Test Summary Test Results: Blue Wool L2 Chamber Type Material Test Method Rotating Drum Flat Array with repositioning Flat Array without repositioning (not recommended) Blue Wool L2 ( E*) SAE J2412 ± 9%Ci4000 ± 5%Xe-3-HS ± 8%Xe-3-HS AATCC 16 ± 3%Ci65A ± 5%Xe-3-HS ± 10% Xe-3-HS

39 Test Summary Test Results: Blue Wool L4 Chamber Type Material Test Method Rotating Drum Flat Array with repositioning Flat Array without repositioning (not recommended) Blue Wool L4 ( E*) SAE J2412 AATCC 16 ± 13% Ci4000 ± 7%Ci65 ± 4%Ci65 ± 8%Ci65A ± 5%Xe-3-HS ± 8%Xe-3-HS ± 8%Xe-3-HS ± 7%Xe-3-HS

40 Test Summary Test Results: Polystyrene Chamber Type Material Test Method Rotating Drum Flat Array with repositioning Flat Array without repositioning (not recommended) SAE J2412 ± 4%Ci65A ± 3%Xe-3-HS Polystyrene ( b*) SAE J2527 ± 3%Ci65A ± 5%Xe-3-HS ± 8%Xe-3-HS ± 12% Xe-3-HS

41 Test Summary Test Results: Auto Alkyd Melamine Chamber Type Material Alkyd- Melami ne Test Method Rotating Drum Flat Array with repositioning Flat Array without repositioning (not recommended) SAE J2527 ± 13% Ci5000 ± 8% Xe-3-HS ± 13% Xe-3-HS

42 Uniformity Conclusions The within-chamber uniformity of degradation for the rotating drum system varied from ±3% to ±13% Depending on the type of material and exposure conditions The uniformity for the static system with manual repositioning varied from ±3% to ±8%

43 Uniformity Conclusions In some cases, the flat array chamber gave better uniformity than the rotating drum in some cases In some cases, the rotating drum was better

44 Uniformity Conclusions The degradation uniformity in the flat array was better when specimens were repositioned during the test However, in many cases... Flat array uniformity was as good or better than the rotating drum even WITHOUT repositioning

45 General Recommendations For Best Results: Manually reposition specimens in both revolving drum and flat array chambers according to a planned schedule Many new test standards require manual repositioning regardless of architecture

46 Acknowledgements I would like to thank the following companies for contributing data: BASF, Southfield, Michigan, USA BASF, Wyandotte, Michigan, USA BASF, Münster, Germany ACT Laboratories, Hillsdale, Michigan, USA Q-Lab Weathering Research Service, Miami, Florida, USA