Measurement of UV ageing of materials. Petri Kärhä Helsinki University of Technology

Transcription

1 Measurement of UV ageing of materials Petri Kärhä Helsinki University of Technology 1

2 Contents UVEMA project Ageing effects Non-spectral test methods Spectral test methods TKK flat-field-grating spectrograph Test measurements TKK UV ageing of materials Slide 2

3 UVEMA-project UVEMA = Effects of UV radiation on MAterials 4 year research project coordinated by FMI Research institutes Finnish Meteorological institute, FMI Helsinki University of Technology, Metrology Research Institute, TKK Tampere University of Technology, Laboratory of Plastics and Elastomer Technology, TTY Companies Elastopoli Oy Oy All-Plast Ab Exel Oyj MacGregor (FIN) Oy Nokian Renkaat Oyj Duration: years starting Financing: Tekes, FMI + 5 companies TKK UV ageing of materials Slide 3

4 Why study effects of UV on materials? UV radiation causes harmfull effects on materials and thus shortens life time of products UV effects can be prevented or slowed down - by selecting materials (not always easy) - using additives, stabilizers and coatings -> Increased costs! Present weather tests nature/laboratory time consuming and expensive -> Increaed costs! Reactions caused and indused by UV in materials are complicated and not fully understood Tests performed at different locations are not fully comparable TKK UV ageing of materials Slide 4

5 Which kind of damage UV causes? Visual changes Color changes: Bleeching Yellowing Darkening Others: Loosing gloss Peeling, Flaking, Hilseily Chalking Erosion Mechanical changes Embrittlement Haurastuminen Microcracking Stiffening Jäykistyminen Change of tensile strength TKK UV ageing of materials Slide 5

6 Which materials we study? Company Materials Properties studied Oy All-Plast Ab Plastic-wood composite painted / unpainted surface quality, tensile strength, impact strength Exel Oyj Reinforced plastics for profiles color, surface quality, mechanical durability, hardness, compression, water absorption, surface roughness MacGregor (FIN) Oy EPDM, natural rubber tensile strength Nokian Renkaat Oyj Rubber composites, stretched mechanical properties, cracks TKK UV ageing of materials Slide 6

7 WP1: long-time ageing in nature Exposure to natural UV and climate on 7 European stations: Latitude: 60,8 N 28,5 N Altitude: m (asl) UV-I (max): 5 13 Pollution: low high Humidity: low high Expected result: Knowledge on effects of various ageing parameters and their combinations TKK UV ageing of materials Slide 7

8 WP2: Measurement of action spectra Goals: 1) Construction and building of UVradiator (spectral measurement) 2) Ageing of studied materials 3) -> Action spectrum, damage vs. wavelength Result: Equipment and methodology for measuring action spectra Results will be used to convert results between test sites in WP 1 TKK UV ageing of materials Slide 8

9 WP3: Characterisation of UV properties of commercial accelerated test environment Goals: 1) Spectral measurement of UV properties (old/new lamps, filters, cleaning) -> UVspectrum 2) UV-spectrum x action spectrum -> UV dose rate 3) Radiation model + environmental factors -> comparison/conversion of dose rate to various natural sites in Europe Expected result: Testing environmetnt whose results can be used to predict behavior under natural environment TKK UV ageing of materials Slide 9

10 WP4: Sample analysis and model development Goals: 1) Measurement and analysis of all samples aged naturally or in laboratories 2) Development of model describing effects of various ageing parameters (UV, T, R.H., O 3, ) Expected results: An improved model describing effects of various parameters on changes in samples tutkittava ominaisuus UVdose ave(t) = 10 ave(t) = 20 ave(t) = 30 TKK UV ageing of materials Slide 10

11 What do we gain? We will have Deeper understanding on ageing effects of a) UV radiation b) other environmental parameters, and c) combined cross-effects; New knowledge on spectral behaviour of UV effects; Better characterised (UV) weathering chambers; Reliable knowledge on UV durability of different materials; Method to estimate life time of products in different markets; Commercial UV testing service for needs of industry TKK UV ageing of materials Slide 11

12 Non-spectral Ageing under sun (accelerated or free) UV weather chamber Solar simulator Spectral Bandpass filters (Monochromator) Cut-off filter technique Grating spectrograph UV testing techniques TKK UV ageing of materials Slide 12

13 Ageing under sun Can be accelerated with concentrators UV radiation to be measured to account for seasonal/weather variations TKK UV ageing of materials Slide 13

14 Weather chambers, solar simulators Typically use Xe-lamps (1 kw 5 kw) Spectrum quite close to solar spectrum TKK UV ageing of materials Slide 14

15 NIST: Integrating sphere with bandpass filters 2 m diameter integrating sphere 8400 W metal halide lamps Band pass filters in output produce monochromatic channels Humidity and temperature controlled TKK UV ageing of materials Slide 15

16 Cut-on-filter technique High-pass filters instead of bandpass filters Difference between two consecutive channels yields change in responsivity within narrow band Widely used and standardized Possible to use glass filters! TKK UV ageing of materials Slide 16

17 Action spectra measured using Cut-on-filter technique Aallonpituusalue, jolla suurin aktiivisuus Polymeeri vaurio sanomalehtipaperi kirkastuminen sanomalehtipaperi villa PVC (kiinteä, 0% TiO 2 ) PC (ei stabiloitu) PC (stabiloitu) polystyreeni vaahto polypropyleeni kellastuminen kellastuminen kellastuminen kellastuminen kellastuminen kellastuminen spektroskopia polypropyleeni venyvyys 0 polyetyleeni spektroskopia 1 polyetyleeni venyvyys (puristettu) 2 polyetyleeni venyvyys kalvo 3 ECO kalvo venyvyys 4 Nylon spektroskopia 290nm 310nm 330nm 350nm 370nm TKK UV ageing of materials Slide 17

18 Grating spectrograph Okazaki large Spectrograph (Japan) 30 / 6 kw Xenon lamps (note scale!) Input slit 1-50 * 100 mm Grating 1200 grooves/mm Horse shoe shaped focal plane Automatic TKK UV ageing of materials Slide 18

19 Starting points for TKK device NIST-style integrating sphere too expensive (>1 M ) Okasaki large spectrograph too big, too expensive. Bent focal plane not good for hard samples Filter techniques not challenging enough, stability problems Monochromator too slow We will shrink Okasaki large spectrograph by factor of 20 and straighten the focal plane using flat-field grating TKK UV ageing of materials Slide 19

20 Layout of the setup TKK UV ageing of materials Slide 20

21 Photograph of ready device TKK UV ageing of materials Slide 21

22 Concave grating Combination of grating and concave mirror -> Reduces one optical component in the setup Flat-field technique results in straight focal plane Produced by Holograte JSC (Russia) according to specifications Diameter 100 mm, 1800 grooves/mm TKK UV ageing of materials Slide 22

23 Stray light shielding TKK UV ageing of materials Slide 23

24 Output properties TKK UV ageing of materials Slide 24

25 Output properties Stray light in output <10-4 (Comparable to commercial single monochromators) Irradiance levels tens of times higher than natural sun light in summer in Finland on nice summer days! TKK UV ageing of materials Slide 25

26 Test measurement: Newspaper Action spectrum measured in hours Result: Yellowing in region nm, maximum 320 nm Differs from literature value, yellowing nm TKK UV ageing of materials Slide 26

27 Test measurement: Polystyrene Result in days Sample measured is protected for solar UV! No changes above 290 nm Literature: nm, maximum 319 nm TKK UV ageing of materials Slide 27

28 Project samples TKK UV ageing of materials Slide 28