This online seminar addresses the influences of weather, i.e. solar radiation, temperature, and moisture on materials including how they are measured and how their impact can be estimated.
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hello good afternoon good morning maybe good evening Welcome to our seminar today um I’m happy you made it to our seminar on the fundamentals of ring part one factors of ring um um your presenter today and you might recognize I I’m not a Native American or not a native English speaker I’m actually from Germany my name is um Florian file I’m working for Atlas material testing technology AS Global manager for client education I’m also a consultant for ring technology and I’m also representing Atlas in yeah mostly European and um some Isa committees together with some of my colleagues and my background is actually chemistry so I’m a chemist I worked yeah quite a while in material degradation first with corrosion later with ring but my basic is actually polymer chemistry and yeah as you might see um my camera is maybe a little bit dark and um it’s already getting dark here in Germany and I work yeah close to our European headquarters in L hlau and yeah that’s who I am and who’s your presenter today and I’m continuing now with a little bit of housekeeping we have a relatively big audience and yeah as you might recognize from my greetings in the beginning relatively some from Europe but most from the United States and the yeah also Southern America I see and so yeah and because we have a relatively big audience um everybody body is going to be muted and however you have the chance if you have a questions or comment during the presentation please take the chance and write down on the question bar on the go to webinar um control panel and I will try to have an eye on it um during the presentation I cannot promise promise but I will definitely follow up on the questions at the end of the presentation if allows and if not the questions are recorded and I will follow up on the questions after the seminar in the next days and yeah and the presentation will also be distributed to everybody who registered with a valid company email address and after the seminar there will also be a short short survey popping up after the seminar I think it’s only three questions and we would be happy if you can ask to give us some feedback on today’s seminar as mentioned today we have part one factors of ring so this is part of a series of different webinars on the topic of ring on revering testing and the principles of revering and these webinars it’s more or less standard low Standalone webinars but they fit nicely together in this series so that’s why we present them typically in this serious form but no worries if you miss miss one we’re going to be repeat it at some point and currently we are starting with a new series and I think we try to cover different time zones but there will be other series of these seminars um coming up in the next weeks and months so if you miss miss something it’s not a big thing you can uh watch them later or look at our recorded seminar as well yeah who are we who is atlas material testing technology Atlas material testing technology is a manufacturer of weing and corrosion test instruments so we have a broad range of instruments of different instrument you might know our big instruments the reters we have mediumsized xenot test equipment Sun test equipment as well so that’s our yeah main focus as manufacturer but we also um have test Services um we have big Laboratories varing test Laboratories in the United States and our headquarters in Mount Prospect close to Chicago um but also here in linen G Alon hlau we have a big test laboratory to cover the European market um we had have Atlas custom systems um Atlas custom system designs and build custom solar simulation lighting system Solar simulation solutions I must say for larger U yeah scale testing uh solar load testing or for the illumination of wind Tunnels for example or bigger climatic Chambers also and yeah lastly we provide provide technical weing support we provide Consulting we provide client education and we are active in standardization and that’s yeah mostly part of my work I’m doing so this was the commercial part now we go into the topics of varing to today we will go into the factors of varing mostly and um yeah we will not so go so much into um ring testing this will be done this will be covered in the upcoming seminars today is to understand where the effect effects of WEA on materials yeah polymers and other materials de create by the effect of WEA by the effect of the environment by the effect of solar radiation but also of other environmental factors and very very obvious very often is a yeah visual change very often is color fading is a primary primary U result of ring degradation ring effects on materials you see in the field and I think everybody of you knows a traffic sign nearby which is faded or a car which is faded so that’s a typical appearance change by the effects of wearing but other effects can happen as well to yeah materials to bul materials like Jing when the surface gets a little bit powdery that’s very often appearing yellow is a typical um appearance change change or gloss loss as well however there are other appearance changes not not necessarily visual appearance changes there are other changes is possible because varing or light degradation affects not only bike materials affects every type of organic materials and this includes also food and beverages for example or cosmetics and these products they might not change visually but they might change their taste or their odor and that’s also an appearance change which can happen and that’s typically only what we see but where where can happen also a lot of other things to the materials by the effects of WEA very often it’s not only um that the dice stuff is deg degrading very often for polymers or for Coatings Al The Matrix is degrading so the polymer the coating becomes mechanically weaker so very often You observe that materials get brittle surfaces crack or you see delamination in general a lot of strength of those materials and there are lot of other effects related to weaing weaing degradation the active ingredients can get degraded and that can be an issue for example for pharmaceutical products when the ACT active pharmaceutical component is degrading by the effect of WEA the pharmaceutical product loses is yeah purpose so it’s function and that’s the really the ve effect of degradation but also polymers um consist of many additives flame retardant herbicides fungicides are added to a polymer to provide protection for the the polymer and those additives actually can degrade you don’t see it maybe the mechanical properties do not change but the properties in general of the polymers of the coding can change and if you look for those properties for your product and you test your product yeah for ring stability and these are the relevant Pro uh properties of your product you have to check those relevant properties after the exposure after wearing to see if the product is still good enough for its per purpose yeah the primary varing factors causing degradation in the environment in is a relation to we we consider solar radiation temperature and humidity water in its different phases which can cause degradation and it’s not only about the quantity of those factors also about the quality the spect Radiance distribution the temperature is where a maximum temperature minimum temperature are that specific times at a specific temperature are there temperature cycles and similar for moisture moisture is typically not a continuous factor it’s typically a cyclic Factor you have wet phes dry phases so you have also a typically a cyclic stress and all of those primary ring Factor and most often together with oxygen which is always always present so we don’t necessarily consider oxygen as a primary reing factor um they cause a chemical stress to a organic material to a polymer and they cause chemical degradation and first you get some microscopic chemical damage you might not see it you might not have a severe um yeah um influence on the tenai strength for example however at some point this damage is accumulating it becomes more obvious it becomes more visible and then you get microscopic damage very often physical damage cracking at a secondary I would say effect of varing and secondary varying factors are also present in the environment secondary varying factors are we could typically consider pollutants biological factors as it rain and on or sea salt for example can be considered as a secondary varing Factor they are typically also present they also contribute to the degradation on materials but in artificial weing we typically need to reduce the stress factors to the primary uh weing factors due to yeah some reason because it on the one side becomes too too complicated and those secondary varing factors are sometimes hard to simulate to be realistic they should be included but again it’s becomes a little bit com complicated however in reality and in weing testing it’s important that in nature those varing factors they act together they act energistically and to get realistic test results if you try to simulate those effects you have also uh simulate those effect simultaneously to get the same synergistic effects as in nature when we talk about varing we talk about typically material degradation in an outdoor environment and outdoor means we have solar radiation we have heat Effects by the Sun by the environment but typically what we have in an outdor environment is also water in the form of rain in the form of you so ring typically includes liquid water when we talk about light f f fastness photo stability testing sometimes just called irradiation testing then we typically focus on most these the light but generally we have relative humidity present we have temperature effects but no liquid water and that’s testing is stupidly done for interior materials where we don’t have um liquid water where we don’t have rain so typically textiles interior Furnitures wallpapers yeah food and beverages Pharmaceuticals are typically tested for an interior climate so typically photo stability or light fastness testing no liquid water let’s go through the different varing factors starting with radiation we will look at rtic quantities we will look at um how solar radiation actually looks like how it’s measured and how very briefly how it affects uh materials so solar radiation is actually a part of the electromagnetic spectrum and solar radiation actually ranges from the UV range to the infrared range and the visible range is in the middle and um so the sun is emitting UVC UVB UVA radiation so UV see from about 100 to 280 nanometers 280 to 350 nanometers is UVB radiation UVA it’s 315 to 400 nanometers um visible radiation that’s what actually the human eye can see it’s typically considered to be the range from 400 to 800 nanometers but these are not necessarily exact numbers everybody has a little different side there a little bit different definitions but for us it’s you like it’s simple 400 to 800 it’s visible part and everything above 800 nanometers is infrared radiation and the critical thing about this IR radiation is the shorter the wavelength the higher the photon energy so the V photons actually have the highest energy and that’s why um yeah it’s not an mystery that UV can cause material damage and it can be critical to material um degradation um not the sun is emitting all types of ir radiation not with the same intensity not with the same irradiance that’s what we call it in um revering um the solar spectrum is actually starting from the UV range ranging over the visible range into the infrared range though so sun is emitting radiation maybe up to 4,000 nanometers but the intensity at higher wavelength becomes relatively low the sun is almost behaving like a black body emitter that’s a body which is emitting um yeah IR Radiance independence from its yeah temperature the sun is um behaving almost like a black body emitter of 2 uh 5,250 de Celsius surface temperature however that’s what the sun is emitting but in between the Sun and our position position on the earth we have the atmosphere and the atmosphere is acting like a filter to solar radiation so especially the outer ozone layer is cutting off actually most of the UVC radiation and that’s a good thing because you we see um low wavelength high energy has a lot of energy photons are very critical can destroy organic material so and yeah should be avoided to be exposed to UVC and the atmosphere is protecting us from the UVC radiation and it’s filtering out many other parts of um the yeah emitted spectrum and what we in principle get when the sun is filtered by exactly one atmosphere is what we should see in red here and that’s the so-called air mass one sun when the sun is filtered by one atmosphere and that’s the case at sea level when the sun is perpendicular so at the equator at the 21st of March and and nor clear sky at noon then the sun is perpendicular and then we have about this spectral Radiance distribution shown here in red with the specific absorption bands of specific components of the atmosphere let’s um don’t want to go too much into detail here however that’s just the spectral idance distribution at noon however the sun is only shortly at noon and only at the equator at the between the tropics in Germany the sun is never perpendicular so we’ll never see Z M as one Z actually here M 1.5 sun is much more realistic however I just did here a rough calculation how the actual spectral Radiance distribution uh would look like um at different times of the day and as you see in red that would be the m one we saw on the other picture and the most time of the day the IR Rance is actually much lower yeah coming back to this reference airas one Z and like many things um everything is standardized everything needs a standard to be referenced and especially if it comes to material development material testing um I just get some message that um there is no audio I can actually it looks like I have audio from my S it’s working so maybe it’s only a single message I got maybe it’s your computer maybe you have to reboot it sorry for that um there’s a reference done and this defined by the international Commission of light and they actually some years ago did a very um yeah um Extended calculation to calculate the reference sun and this was published actually in the publication number 85 table four um it’s the rence sun when the sun is exactly filtered by one atmosphere and that was for many years the reference Sun we have been using in revering however this was recalculated and recently republished as cie 241 and here it’s not table four anymore it’s cie ag1 is a reference sun which is more or less the same Sun as um the old reference on but the resolution is better it’s better calculated a better model it’s relatively similar it’s not identical and in the near future all varing standards will change from referencing CIA number 85 to reference theia 241 but that’s unnecessary background information now at this point I would say what’s more important is at the reference sun has about 7% UV so relatively small portion about 55% visible radiation and about 38% infrared radiation and again the higher the photon energy the higher the um the shorter the wavelength the higher the photon energy the other way around um and the more critical actually the photons are and that’s the reason why UV photons are the most critical even if it’s only 7% here we typically observe the most damage however the lower parts the blue light um the purple light the high energy visible radiation can also cause direct photochemical damage however the longer wavelength visible um radiation and infrared radiation typically does not cause direct photochemical damage however can heat up materials to quantify solar radiation we not so much interested in the output of the light source we are interested in what’s received on the surface and the radiant power on a surface is what we call a Radiance and the unit here is watts per square meter and the symbol for radiance we typically use an e so energy flux on a Surface intensity on a Surface that’s the E Radiance and we can look either at the full IR Radiance or we can look at a specific wavelengths at a specific yeah 340 nanometers 420 nanometers at the spectral irradiance the irradiance the intensity on a Surface at a specific wavelength that’s the Spector Radiance if we want to know the full amount of energy in a specific time frame which is delivered on a Surface we look at the radiant exposure and that’s the time integrated a Radiance so energy per surface and here’s a simple is typically an AG so we have an annual radiant exposure the full amount of solar energy on a specific surface in a specific area that would be radiant exposure and also here we can look at the full radiant exposure or the spectral radiant exposure to measure solar radiation we typically use so-called radiometers so a device which is designed to measure solar radiation and there are different types there are so- calleded pyranometers they measure yeah typically the global radiation the full amount of radiation all wavelengths and all directions and a panometer can be relatively similar it can be just a um painted um pieces of metal black and white and by the temperature differ between the black and the white area this simple panometer can be calibrated to measure the global radi ation however today very often photo diodes are used to or other photosensitive elements are used as parameters parameters are relatively similar but they measure only the direct solar radiation so need no diffus solar radiation so typically a parallelometer is a yeah also a similar sensor but it’s on the bottom of a tube so that only the um direct solar radiation can hit the sensor then we have the high-end instrument the spectral radiometers they can actually measure the solar radiation wavelength by wavelength so that gives you this full amount of the spectral erance distribution very good to have but very complicated to monitor continuously a light source with a spectral radi meter so we so typically not done to monitor long-term exposures for example filter R meters are relatively similar to pyranometers so you have a photosensitive element but covered with an Bend pass filter which is only transparent within a specific Bend path of the wavelength so between a specific wavelengths and that’s what we commonly use in weing outdoor weing artificial weing because these are relatively simple instrument but but you can relatively controlled look at a specific wavelength range so and there are narrow band filter radiometers typically wavelength mid uh half wave uh wavelength ranges between of less than 20 nanometers there are Broadband um so in a medium wavelength um half wve range and whiteband filtery meters a available we will see examples of these measur ranges on the next slide so typically when we look at the um spe spectral erance distribution we are interested in the intensity so the radiance and the full amount of energy in a specific time frame and so give you some somehow typical numbers these are not maximum numbers these are not specific numbers but a typical irance value if you look at the total irance from all wavelength ranges is about th000 watts per square meter if you look at the reference on the reference sun is a little bit higher but that’s a typical maximum value we consider as one Sun level and for example the annual radiant exposure in Miami um so the full amount of radiant solar energy delivered on a Surface in Miami is about 6.7 GJ per SC meter if you look at the for range however you can just look at the UV and the visible range and that would be a typical wi Bend radiometer range so there are white Bend radiometers available which just look at the wavelength range from 300 to 800 nanometer and here the equivalent value actually would be 550 wats per square meter s IR Radiance and about 3.6 g g per square met um radiant exposure and you can look at the total Spectrum just look at the UV range if you use a um Broadband radium meter and here typical range is from yeah 300 to 400 or 295 to 400 nanometers and here the equivalent value would be about 60 wats per square meter from the a radians and about 400 Mega per square meter and you UV radiant exposure from 300 to 400 nomer or you look just at a one wavelength with a narrow Bend radiometer and here the spectral Radiance in the almost middle of the UV at 340 nanometers would be 05 butt uh 0. 51 watts per square meter and nanometer as spectral Radiance at 340 nanometers and the annual radiant exposure the annual spectral radiant exposure at 340 nanometers would be about 3.3 Mees per year so in principle if you would look at the sun with these different type of radi meters these would be the values you measure as a radiant and as the radiant exposure I mentioned it briefly um I typically talk about total solar radiation when it’s about all wavelength ranges however sometimes you hear the term Global radiation and Global radiation means solar radiation from all directions and that all um radiation is hitting a surface directly from the Sun or is reaching a surface directly from the sun because as mentioned we have the atmosphere in between the Sun and the surface and the Sun is acting like a filter so some parts are filtering filtered out some parts are reflected but also some parts of the light are scattered and there are different type of scattering there are particle scattering with Vulcan which is the German words word for clouds I have to correct this in the slides um and particle scatter solar radiation um independent of the wavelength so no matter um which wavelength it’s gathered into all Direction almost similar so clouds or partic scattering does not change the spectral e Radiance distribution and the human eye is actually trained to observe the global solar radiation the light of the global solar radiation the visible part and has white light and that’s why the clouds appear to be white because there’s no shift in the spectral erance distribution however there is also molecular scattering also called Riley scattering and that’s wavelength dependent the higher the photon energy the higher the interaction between the molecule and the photons and that’s why short wavelength photons are scattered more comp to longer wavelengths and short wavelength means for the visible part the blue part is scattered more compared to the red part so a solar beam which is not directed into my direction I typically would not see if there would be no atmosphere but the atmosphere is actually scattering this solar beam and it’s scattering the blue part more compared to the red part that’s why the light light I see coming from the atmosphere from the sky appears to be blue because of Ry scattering same reason especially in the evening when I look directly in the sun which is never a good idea but anyway the reason the sun looks yellow and maybe reddish in the evening is there’s a deficiency of the blue light light due to Riley scattering that’s why we get the shift into the other direction less blue r makes this light appear to be yellowish reddish so that’s R this scattering and why I’m telling you this we have a lot of diffuse radiation especially in moist atmospheres like Florida yeah but also Europe Northern America and moist environment when um you have clear sky but a lot lot of moisture in the air and water has a big effect on R is gathering and with this rer is scattering you get a lot of diffused light and okay there’s no direct light but the diffused light can be rich in UV and that’s the reason why you can even get sunburn in the shadow because of Riley scattering and here just to other calculated examples to show you the effect of Riley scattering um in green we have the global solar radiation and Global radiation is the sum of d direct and diffuse radiation and in yeah purple we have the diffuse radiation and red the direct part and if you have a moist atmosphere here 80% relative humidity but still clear conditions you get a lot of Ry gaing and actually in the lower wavelength part of UV you have even more UV in the diffuse radiation with this calculation with this model compared to the direct part in a dry area like Phoenix for example not much humidity in the air so not much or less Ry scatterings there some R scattering going on here but not such a big effect like um for um yeah Miami for moist atmosphere so another effect um on the spectral Radiance Distribution on a surface is the so-called albo reflection um this is relevant for inclined surfaces um because you have an additional factor factor reflected solar radiation from the environment can be a factor in urban en environments where you have a lot of glass facades typically mostly reflected in the visible range but there are ground covers which reflect some UV also and this radiation contributes also to the radiation received on a specific surface and so you have to know the ground cover where you yeah specimen where your samples where your surfaces are to understand all of this and yeah just to give you L numbers and again the um reflectance it’s also a spectral value so the spectral reflectance depend on the ground cover and different re regions of the spectrum are reflected differently dependent on the ground cover yeah it’s more complicated than just sunlight and it even becomes more complicated um the amount of solar radiation received on a Surface depends on the exposure angle when the sun is perpendicular and that’s what we call Direct normal incidence we have the highest intensity the highest IR radiance and the Iranian actually decreasing with the coine of the angle um the sun is yeah hitting the surface so you get the highest amount of solar radiation when the sun is perpendicular nothing new in northern Europe in Germany our Vineyards are typically on south facing Hills very steep to catch as much sun especially in summertime as possible um yeah to optimize the exposure of the grapes and yeah same is typically also relevant for materials for products exposed to environment so in the northern atmosphere on the 21st of March for example when the sun is perpendicular actually at the equator a horizontal surface is not at dni at this time of the year however what you can do you can incline your exposure surfaced towards the Sun and if you do this at the latitude angle you at you can actually mimic a yeah um yeah a tropical a perpendicular exposure with your test specimen even in on the Northern atmosphere or in the southern atmosphere far away from the equator you still have the longer wave length the path length through the atmosphere with the side but you at least can optimize the exposure angle to catch as much solar radiation on the surface as possible and so the amount of solar radiation depends on the exposure angle and each time of the year at noon um the Expo the sun is at at a different position so a horizontal surface but might be better in summertime in the northern atmosphere um compared to an at laude exposure so it depends on the time of the year which angle actually would be the best angle for the exposure so and this definitely also influences the pattern throughout the year so it’s important to know the surface orientation um your product will see or the data you receive are from that’s very important to consider and just to give you also some examples here how it can look like here we have the exposure angles of 5° which is almost horizontal we have 34° that’s the latitude angle of Phoenix Arizona and 45 degrees which is a commonly yeah exposure angle used in ring for historic regions and compared those one on the one side the total solar radiation which is relatively evenly distributed in these inclin exposure so we mimic a Tropical Exposure a horizontal um yeah not horizontal a yeah a tropical an equator exposure in principle with the um inclined surfaces so it’s more evenly distributed throughout the year in summer time it’s not the optimum angle so the horizontal surface receives actually more solar radiation and in winter time it receives less solar radiation so it’s more evenly distributed throughout the year and if we look at the radiant exposure throughout the year it’s actually also the maximum r exposure um for the um latitude angle inclined towards the sun in thec effect is not as big why because we can only influence the direct share of solar radiation um with the exposure angle the diffuse solar radiation acts more or less the same on each surface and there’s a lot of UV radiation in the diffused part even in Phoenix so the effect on the UV is not as big as for the total solar radiation so that’s also something which has to be to considered briefly to look at the maximum natural a Radiance we see typically in the field in the outdoors and I mentioned it briefly earlier it’s about thousand thousand watts per square meter and typically what we consider at maximum um irance in the v it’s about 60 watts per square meter so a typical not worst case but a typical maximum value um which happens in nature and here just for your reference to give you an overview about typical annual radiant exposures um from our exposure sites throughout the world we have exposure site in Miami in Phoenix but also one in Europe in Zar in Hook from Holland in the Netherlands and yeah just for rence reference you can look at those numbers and one thing I just briefly want to point out in for historic reasons in outdoor weing we typically use fi radium meters from 295 to 385 nanometers in art artificial ring for historic reasons we typically use UV filter radiometers from 300 to 400 Nom so be careful if you hear about your v data data from outo exposures when you convert those for artificial exposures because the range can be different but you can roughly transfer it within conversion factor from one to each other typically for natural solar radiation at least yeah here’s just for your reference also a word radiation map to give you some idea which areas in the world on the world receive a lot of solar radiation so typically that’s not the tropics where the solar angle actually would be the best but the tropics are very often Cloud covered where have a lot of rain so and that’s again filtering out um a lot of solar radiation so actually the highest amount of solar radiation is observed at the tropics in the northern atmosphere and in the southern atmosphere and in high altitude areas yeah the effect of solar radiation on organic components um first solar radiation has to be absorbed to cause an effect this effect can be if solar radiation absorbed that that an molecule is transformed from its electronic round State into an excited state so you have an excited molecule which has a lot of energy and typically an excited molecule wants to get rid of this energy and mostly this energy is emitted in the form of heat or in the form of light fluos sense phosphorous sense however sometimes and that’s relatively seldom but sometime it can happen say this energy is um um causing a reaction for example with oxygen or other components and then the photo degradation is starting photod degradation processes can be photo oxidation other process process is typically involved with radical reactions and radical reactions are typically chain reactions so typically one Photon causing the um resulting in um the in a radical can cause multiple damages in a polymer so but we have other seminars just focusing on photodegradation so I don’t want to go into detail on that here at this point the spectral sensitivity of a material def describes the wavelength range where the material is sensitive sensitive to photo photo yeah to photons so and typical typically the material has some spectral sensitivity in the UV it does not necessarily be only in UV it can also be in the visible range especially dice stuffs very often have specific spectral sensitivity in the visible range and on the other side you have the light source the radiation source and in the areas where you have photons present and you have a spectral sensitivity so when the two curves overlap that’s the area where you can actually um observe degradation and the higher the photon energy the more severe the degradation and the overlapping area can can also be calculated and that’s the so-called activation spectrum and that’s a very material specific properties so and if you shift the light source to an unrealistic we cut On You’ get a different overlap you might get an overlap with other spectral sensitivity so typically one material does not have a single spectral sensitivity can have different spectral sensitivities resulting in different reactions so and so if if you have an unrealistic UV cuton you typically get unrealistic degradation yeah to summarize on solar radiation solar radiation is influenced by the atmospheric conditions by the pathway through the atmosphere so it depends on the area you are the season the daytime the weather conditions and how the surface is orientated and solar radiation is actually initiating photochemical degradation which leads us to the second factor of ring and it’s a little bit shorter than the other one um I might not be completely finished in 15 minutes but I try to be on time as possible so maybe 10 past the hour I should be at the end um temperature um um of irradiated surfaces are described how they are measured and what effects we are going to have and it’s actually not a big surprise um everybody knows this the darker a surface exposed to solar radiation the higher the surface temperatures typically so and here we just exposed PVC coated aluminum plates in Phoenix Arizona again uh throughout several days and we measured the surface temperatures and we see yeah no big surprise um all surfaces even the white one um gets hotter compared to the ambient temperature and the higher the eress during the day the higher the temperatures and we see this temperature splitting between the different colors so no big surprise and actually let me go to this slide first so we have the solar radiation coming in on the surfaces however there’s also thermal radiation and each body in a field in the environment is emitting heat energy at a much longer wavelength range compared to solar radiation and in an outdoor environment we have a lot of incoming energy from the global radiation depending on the absorption on the reflectance so on the color of the surfaces and on the one on other side we also have incoming theral radiation from the environment and we have Thal emission from the surface we looking at and during daytime we have a specific balance which is on the positive side so we have more incoming energy compared to the energy loss so we have a heating up of the surface during the daytime however at night time when there’s a clear sky the sky has relatively low thermal emission but the surface is still losing thermal energy so it’s losing actually at nighttime more energy and it’s receiving that’s why at night time surfaces gets cooler compared to the ambient temperature to this thermal emission effect to the radiation um heat balance yeah that’s actually the same described here in daytime you have the solar heat coming in but you also have thermal emission from the surface you have the incoming solar radiation from the EnV environment as well so you have the thermal heat balance in nighttime you don’t have the incoming solar radiation but you still have the balance between the environment and your surface but that balance is on the negative size so you lose more energy so the surface gets cooler there’s a specific case then you have a um um separate area and that’s a typical greenhouse effect when you have a surface in an enclosed cabin and an automotive cabin typically has Windows and Through the Windows solar radiation can pass through mostly the UV part uh is filtered out but the visle part can pass maybe some infrared part can pass and heating up the surface inside the cabin and the surface in in the cabin the seed the uh windshield uh the amateur um Shield here and the other parts inside the car are heated up and emitting energy however now you have an enclosed cabin and you have the glass between the environment and the [Music] um and your surface so this exchange with the environment is actually um prohibited and you have the glass which is also a thermal emitter acting into both Direction so you get a yeah greenhouse effect you get this extreme heating on those surfaces in the interior of a of a car and that’s the um yeah greenhouse effect in the interior of car so just to give you some numbers on typical maximum daily imian temperatures we observe in our outdoor fields we have um here data from chenai in India Miami and in Florida Phoenix Arizona h from Holland in the Netherlands and the and France and what we see here is the frequency of occurence in a sixe frame how often specific daily maximum J ambian temperatures ured so yeah and we see we especially in I and Phoenix we frequently see temperatures above 40° C air temperatures not so often in Miami and yeah in the European countries yeah not so often so but so 40 degrees celsius I would say it’s a relatively realistic maximum temperature in an outdoor environment and many ring standards have maximum temperatures or chamber temperatures air temperatures in the range of 40° CI so relatively realistic however in weing we are much more interested in the surface temperature of our test specimen and in general It’s relatively complicated to measure the surface temperatures of individual exposed samples so and that’s why in weing we use reference temperatures and of course you want to have somehow severse case reference temperatures and that’s why we use black painted metal sheets black painted metal panels as reference temperatures unfortunately there are two different types of black panel black standard sensors defined the so-called black panel sensor is a black painted metal sheet without insulation on the back side um and the black standard sensor is very similar but it has a polymer insulation on the back side so it shows a little bit higher temperatures compared to the black panel the problem is the surface temperatures also depends on the air flow the wind speed and the yeah environmental conditions not only on the radiance and the the surrounding air temperature so there’s unfortunately not a fixed difference between the black panel and the black standard temperature typically under irradiation black standard has a higher temperature however the difference can be 2° it can be 10 degrees depends on the whole setup of the system and that’s a little bit unfortunate so the reason why we have two different type of sensors it’s a little bit historic American standardization for many years preferred and used the black panel sensor which is shown here on the right ISO standards um yeah prefer historically the black standard sensor most standards today allow both both options but the results may be different because of the yeah unknown temperature difference so be very careful when you test according to a standard in selecting the right St uh sensor type that’s very critical on the degradation and there are similar sensors to represent the lower limits of a park surface exposed to the environment and it’s the white panel or the white standard sensors relatively the same and also here to give you some numbers the frequency of occurrence of specific black panel or black standard temperatures at the same sites in India in the US and in Europe and again chenai Miami Phoenix sometimes we observe surface temperatures above 70° cius very seldomly above 80° cus with these sensors and coming back to standardization standards very often use black pen or black standard set points in the range of 65 63° depends on the sensor type you’re using which appears to be relatively high but you are not at the worst case conditions you at relatively normal maximum conditions I would say with these temperatures so again standards here for weing relatively realistic to give you some numbers why are temperatures so important very briefly temperatures influence the reaction speed and this also applies for degradation reactions photochemical degradation processes the higher the temperatures the higher the the faster the degradation there is a very rough ruler Thum and I hear some of um my colleagues from standardization already yeling right now um because um this rule of thump is really very rough it most often does not apply it’s most often disobeyed but to give you some idea of effect of temperature a temperature decrease of 10 Kelvin doubles the degradation rate that’s can be the magnitude of effects of um temperature um but the exact influence of temperature actually has to be C calculated and there’s the so-called arenus equation that you have to consider other factors like activation barrier and so on to really calculate the effect of um temperature increase on material degradation and this real effect this real acceleration rate by temperature is very specific to the polymer to the material and also the property you’re looking at it can be much less than the 10 uh than doubling the reaction rate it can be much more than doubling the reaction rate so just to point this out another effect of temperatures on materials is the material phase temperature increases can cause phase transitions melting but also almost unnotable noticeable phase transitions like the glass transitions a polymeric material typically has a glass transition temperature below the glass transition temperature it’s more yeah um yeah harder it’s more vitous glass-like above the glass trans temperature is more rubbery more elastic and of course reaction rate rates diffusion rates are different below the um glass position temperature and above the glass position temperature so the influence of weing effects will be different and in reality you should you test your material as close to the real conditions as as possible and if it’s only maybe above the the glass transition temperature um throughout maybe through minutes of the day or maybe only once a year or twice a year and you test continuously above the glass sensation temperature you test in principle the wrong material so you have to be very careful with the test parameters in artificial testing to consider an appropriate temperature for the glass notation temperature that’s very critical and most often or yeah one of the most reasons I don’t see good wearing results or very often is that the glass transition temperature is not considered that’s very critical and just to give you some examples of typical glass transition temperatures glass transition temperature depends always on the formulation of the polymer so these are not exact numbers so elevated samples temperature um cause higher diffusion rates higher reaction rates phase transitions um effects of heat can be expansion contraction so a mechanical effect evaporation condensation can happen so evaporation of ADI but also of water condensation of water at lower temperatures and there can be also thermal aging this brings me to the last and the shortest ring factors um Factor moisture you will briefly quantify the typo here and effects of moisture on materials so typically to quantify moisture um to give you some uh value some Expressions here some terms here is the absolute humidity it’s not so commonly used it’s a density of water vapor the density of air so in grams per square meter but you more commonly see the relative humidity the amount of water in the air but this factor is actually the um a um yeah relative Factor because this water amount of water vapor is compared to the amount of the amount of water vapor the air can hold when it’s saturated so a percentage of saturation and the hotter the air the more the higher or the more water it needs to get saturated sometimes we see the D Point as a quantification of air moisture and the Vio is actually a temperature it’s a temperature at which the air starts to condense at a when you cool it down at a specific um relative humidity for example a specific absolute humidity so that’s the point when the relative humidity actually reaches 100% when you cool down the air then very important factor is the time of wetness that’s just the time a surface is vet in the environment so vet can mean by rain and here we have the average monthly rain from our outdoor sites average over several year years um at the different sites and obviously Miami chenai subtropical tropical climates um very high amount of rain so a lot of moisture there are some seasonal variations but General each month very wet then we have sari Su a lot of rain in wintertime not so much in summertime and H from Holland in the Netherlands a lot of rain throughout the year I would say and it’s from Holland it’s northern Europe um middle northern Europe I would say it’s cold rain not a pleasant weather um however Phoenix um also some rain in wintertime but almost no rain in summertime so overall the lowest amount of rain then we have the relative humidity at these locations and actually showing here in the bigger bars here the um average um um um relative humidities at those SES and we see a similar order like on the with the r and Phoenix also the lowest amount of relative humidity but what you actually have to look at and you might see it on the screen slightly it’s the upper and the lower limits here for each location and that’s the range of the relative humidity and typically again average value shown here but relative humidity is typically very height at nighttime because the temperatures are low and the relative humidity is typically low at daytime because the temperatures are high so that’s typically the upper and the lower limit which shows up here is actually the average daily cycle of relative humidity you experience in the different locations and if you look at Miami Phoenix but also yeah um H from Holland evence you’re almost at nighttime close to saturation so it’s close to um du formation actually that’s the next slide um typically throughout the day you have the maximum temperatures yeah somehow in afternoon after late mid-afternoon maybe you have maximum air temperatures and as mentioned the relative humidity percentage percentage of saturation hot air can pick up more moisture so typically at daytime the relative humidity is low because the air is warm at nighttime the relative humidity is high because the air is cool however if you look now at surface temperatures and they heat up mostly during daytime but they cool down and they cool down below the air temperature at nighttime and at the boundary climate between the air and the surface temperatures you get into actually oversaturation much easier and that’s the time of the day you get du formation so time of wetness on the one side by rain but even more critical is a time of wetness by you and that’s the case in tropical subtropical environments Florida ji but also Europe Northern America many areas have du formation almost every day so a critical factor of weing is done by du and it’s um yeah um very um important and in reality um we can measure the time of wetness which is a little bit comp complicated so we um measure it continuously but the data that’s another story but here we have some data at different angles on relative on time of wetness actually measurement in Florida and we see we have some dependence on the exposure angle because of the amount of rain which is perceived on the surface but also on the fastness of drying when the sun is shining and also how fast the water is pouring off does all influence the time of Ness but overall it’s about 50% of the time a surface is exposed in Miami the surface is wet it’s a really critical factor and Phoenix on the other side much lower um time of wetness yeah here just briefly how do the different ver factures actually interact with each other so we have actually let’s start with the solar radiation here on a clear sky day in Miami which is relatively seldom um where you have no clouds at all and you see the re idance Rising during the day reaching a noon uh maximum at noon following that is the air temperature shown in red here and the black panel temperature shown here in black and yeah a relatively warm day um 50° black panel 30° um um G air temperature if you look at the relative humidity it’s yeah close to Z duration at nighttime getting up to 50% during daytime and then back to um yeah close to saturation at night time from that you can actually calculate the um absolute humidity and the due point and this is actually relatively interesting that the absolute humidity throughout the day is actually in the air it’s relatively constant you have a slight increase in the morning through the drying of dew but it’s not changing very much so the total amount of moisture the absolute amount of moisture in the air is a relatively constant Factor um it’s more seasonal ring in Miami so the different factors influence each other and the critical part about moisture is very often the moisture cycles and very often these moisture cyes are relevant for yeah polymer or coating degradation and here we have an example where a coating was exposed to spectral irradiation and there was actually only yellowing with uh just irradiation but if moisture Cycles have been applied then cracks occured so crack formation surface cracking is very often a combination of Aging by uh photochemical aging and Cycles cyclic stresses by moisture Cycles so for realistic simulation moisture is very critical and there are other effects of moisture like thermal shock which is relevant there’s erosion effects impact effects and there are also degradation reactions especially for hydrophilic polymers um which can be only caused by Water by humidity hydrolysis effects and so on there are a lot of secondary R factors um I briefly mentioned them in the beginning it’s hard to simulate them you can simulate them yeah somehow in the field sometimes as it rain microorganism and others I will not go into details here but you have to consider them if you transfer your test results to reality yeah to understand the effects of the environment on your material you have to understand the environment you have to understand climate climate is what we expect weather is what we get Mar train and there’s a difference between weather and climate WEA is the status of the atmosphere at a specific point of time and climate typically describes the longterm pattern so if you produce or develop a product for a specific Market you have to understand the climate in this market and there is some guidance given by the so-called C Giger classification which is yeah somehow simplifying different climate types into a two or free letter code describing the climate so erid um medit uh uh um and moist or um moderate with wet Summers so it’s relatively good described and it’s actually freely available um I think it’s written here somewhere the web page or if you go Google ker you get the whole classification for free for download from done sources so it’s not complicated to get the uh information it gives you some ideas on a climate for a specific region um if you develop a product for a specific region and that’s what we typically do um I mentioned I work in Consulting and we develop test programs for many products in the history and what we typically first do is to do start with with a climate analysis and if the product goes into different areas and here’s in a product which was used for transportation um for um aircrafts and for ships and we first start with a climate analysis of all the regions the product will see and we let do some assignments according to K Gyer compare the um environmental parameters and we see the different areas group up so you get some idea of those behavor of the stress effects in those different climate um areas the product will actually end up it’s probably not as comp complex for many products as here but um that’s how to start with to understand the WEA factors and if you understand the we factors you can understand how your product will actually react to the bever factors and that’s it for today um actually next week we will go into Auto weing actually don’t know if I’m going to present or if one of my colleagues is going to present I think it’s one of my probably native speaking colleagues who is going to present next week on outdoor weing on the test site on the outdoor weing technology yeah please use our knowledge resources um you find them on the web and when you get the presentation you get all these links you can directly click on to find our knowledge resources we have a relative new wearing blog um which is currently populated I think I already already posted one um post and yeah please follow us on LinkedIn and for future seminars and you found this seminar today please visit our client education calendar um I already talked a little bit too long and I don’t see any incoming questions if I don’t see any incoming questions you have our contact details please you can write us your questions anytime afterwards um the presentation again will be distributed and please take your time to fill in the short survey after the seminar that’s it from my side yeah you’re welcome and um I hope we meet each other as another seminar have a great day or a great evening and goodbye thank you