This online seminar addresses the principles of how to accelerate weathering tests and what has to be considered to avoid unrealistic results. Mathematical/statistical procedures are described on how to compare and how to validate weathering results from different exposures.
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Hello good evening good afternoon good morning everybody my name is Andreas rle and I’m your host and your presenter of today’s online seminar this is part five of an Atlas series of fundamentals of weathering online seminars thank you very much for being here today for attending virtually and the topic of today is
Acceleration before I start with introducing myself and the company and going into the topic a few housekeeping items here this presentation will be 1 hour we will distributed via a link after the online seminar if you have questions please feel free to type the question or
The questions into the box that you see in your control panel I will address your questions at the end of the session I will try to conclude a couple of minutes earlier depending on how many questions are coming in um if you have follow-up questions which always uh is welcome please go to
Our website and click on the contact us button on one of our websites we have it in different languages click on the contact us button type in your request suggestion recommendation or question and somebody will come back to you somebody who speaks your language and somebody who is located in the area that
You are from also check out our online seminar calendar for other topics that may be of interest for you I have put the URL down here you don’t have to write that you will get the presentation anyway all right now a few words to myself and
To the company for those of you who do not know Atlas well my name is Andreas as I told you before you may have realized from my very strong accent that I am not an English native speaker I’m a German my background is in physics biology and chemistry I have about 30
Years experience in material and product performance Tech testing standardization test me method development before I joined atas in 1999 I worked for the industry Association of Caravans and motor Caravans and was um director of Technical and environmental Affairs back then also dealing with with ISO and Cen and then and asdm
Standards I’m chairman of the SK Symposium on WEA ring of plastics and um session chair at European Ving Symposium or us conferences sometimes if time allows our company Atlas material testing technology has quite a long history we have been around for much more than 100 years our specialty is
Weathering and we are the market and Technology leader in weathering instruments we also have a line of corrosion instruments our laboratory services and Outdoor Services are frequently used all around the world we have sites a big network of testing sites one of our activities also deals with customade solar simulators scalable
The picture below here on the the left it shows a huge solar simulator where you uh can put a train or car or even a fighter plane under to uh investigate solar load um similar kinds of light sources are also used for high-speed lighting and Technical lighting purposes and we are producing those
Custom made systems as well last but not least we are quite active in standardization commit representation we are also um having um yeah a very let’s say Advanced uh program of client education seminars for beginners but also for um for advanced uh uh people up to Scientific
Level and uh we also provide Consulting to our customers um especially with regard to applications and to test method development so this should do it that was the commercial 5 minutes into today’s presentation the right time to start we are in part five right now of the series of fundamentals of weathering
Just for your overview you should know that there are other parts one two 3 four and part six as well it is not um mandatory that you listen to all these parts in this order so you can go into the outdoor weathering next or factors of weathering and then correlation then
Test methods so the order is not important um you should you should listen to those classes whenever your calendar allows all right today it’s acceleration time this is the outline of today’s slides acceleration Factor will be the first then examples for acceleration factors I will talk a little bit about
Time compression and a little bit more in depth about intensification of specific weathering parameters to uh achieve higher acceleration and I will end with a summary a common question for everybody dealing with weathering is what is is the acceleration between my Laboratory cenon test and static Auto exposure as you may
Have heard either myself or one of my ‘s colleagues say before this is without any doubt the most often asked question we get literally on almost a daily basis the question is often worded to be more specific as how many hours in my WEA Omer equals year in Florida or in chenai
Or in SAR or in Phoenix Arizona even though you are all muted right now I can imagine the nodding of heads and all of you saying yes that’s what I want to know and expect me to give you the magic number the second most asked question
That is always or at least should be what or how good is the correlation between these exposures laboratory to field or laboratory to Outdoors but actually this last question should come first because High test acceleration by the s able is meaningless if the results don’t correlate I hope you agree so fast
Test with bad results is useless but what information can we use to potentially predict test acceleration beforehand which we often need to estimate a test duration well starting point maybe to compare the cumulative radiant exposure some call the dose or dosage I don’t like that because that is
Coming from other fields like medic medical signs or radioactivity and is usually used for absorbed radiation so let’s stay with the um the right term radiant exposure um for a Target autolocation to that same radi exposure our Laboratory test the comparison of these two here’s
An example how how long should I test in weatherometer to simulate one year of exposure at the a test site in chenai India well we know how much rated energy we receive at this location and I put that here it is 400 megga per square meter per year on
Average now let’s say that we are running a Laboratory test in a cenon AR instrument following method a of ISO 4892 part two and this is 60 watt per square meter using an outdor daylight filter set without dark phas rain is included but no dark
Phas so we have 60 wat per s meter in the instrument and 400 Mega per square meter to achieve how long does it take it’s quite very easy and quick calculation I will I will guide you through that we start oops is it aha so we have the annual radiant
Exposure in chenai 400 Meg per square meter we have the radiance of the laboratory instrument of 60 wat per square meter and the formula is radiant exposure is IR Radiance time time W per square met time hours it’s what hours or seconds which is J seconds um
And this is radiant exposure there the formula again we um change it to have the time here which is radiant exposure divided by Radiance I choose the values because they are easy to calculate um yeah without a calculator 400 megga plus square meter divided by
60 watt per square meter watt is J per second so J per watt is a second it’s very easy is 400 divided by 60 which is 6.7 um mecs million seconds 10 to the 6 which is 11 weeks and then the acceleration factor is 11 weeks divided by 52 weeks because
Year in chenai and by the way everywhere else is 52 weeks and this leads to the acceleration factor with an index e meaning ER Radiance only of 4.7 so now let’s go back to the red disclaimer that I had put down here this is only a rough estimate based on
Radiation only what we neglect is temperature relative humidity brain and all secondary weather factors as well and the most important neglected property here is the material response to the weather factors so we are calculating acceleration factors only based on weather data acceleration factors should always be calculated or determined not
Calculate determined by looking at the material response right so this is very important to know what we just did it’s a very rough estimate but I calculate here in this short calculation some of our colleagues say Andreas don’t show that we shouldn’t talk about that we should you know not
Misguide people to do these calculations I think it is it is good that you see that but that you get the full disc claimers the full cautions the full um explanation what’s behind it it’s only a rough estimate it doesn’t include any material property any temperature any
Rain and humidity all right so what is an acceleration Factor then in general we have the blue curve here which is a property change over time x excess is time after a certain time in field the the past fake criteria is met this is characterized by this red line and this
Is then called service live if we have a faster test which doesn’t distort the mechanisms we reach that service live after a shorter time because it’s a faster test it’s an accelerated test and these two times divided by each other is the acceleration factor it’s as easy as
That it’s very very very easy very simple the definition is very simple but what’s behind it is very complex in all accelerat testing not just weathering we have only two possibilities for test acceleration the first of these is time compression the second is intensification and here are
The um yeah the definitions of a German vdi that’s Association of German Engineers standard 3958 page one these are the the two um definitions in English usually you don’t deal with time compression it’s all called acceleration but in in in German language we differentiate and there is a
Reason why we didn’t differentiate you will see very soon so let’s look at the time compression how do we achieve it for most traditional laboratory weathering test methods with artificial light sources such as the common ACM ISO AC methods the radiance level is either at or even below the maximum solar
Intensity you would see during Peak Auto exposure such as summer Moon time but of course in the laboratory we can run at these conditions continuously and just delete the dark the dark uh night times you see that and then we have the same integral here which is the radiant exposure
Because this is the radiance and this is a time I just told you that um radiant integrated over a time is radiant exposure and then we get to this same integral here but in a shorter time and this is called time compression so the compressed test the time to reach a
Specific rate exposure is much shorter than aors that’s the whole trick many basic test standards specify typical Max maximum values for the key testing parameters for example the 60 WT per square meter which I just uh um used in my quick calculation is a typical maximum natural non Radiance 65 Celsius
Is a maximum temperature frequently occurring at noon in extreme climates such as Phoenix or chenai measurement data of all these values and how they are derived and how the test methods are um uh derived from The Real World data this is dealt with in the in other parts of that fundamentals of weathering
Series in the out part and also in the standard part but here are some basic CLR test cycles for Plastics Coatings and textiles and acg1 155 um General all right now let’s have a look at a couple of examples from literature the first example is for an
Auto Automotive base code or clear code material base code clear code material running at what would be considered pretty standard latory test conditions for an auto application in the cenon AR instrument note that this study is quite extensive reviewing data from over 22 years of studies 22
Years for many tests and materials we see cenon tests to often be in the range of about four to six times or Florida and maybe close to double that for North Central Europe so the 27 x number versus Europe is really surprising based on a comparison of the
Solar radiation number this is higher than the comparision of solar radiation example number two is also on Coatings note that the test method is quite similar to the example number one with compar Radiance black standard and relative humidity set points but note the acceleration factors to South Florida are 50% higher six times
Compared to four times in the previous example and the comparison to Central Europe was 20x or about 25% slower than the previous example but still much greater than the approximate doubling that we would expect if you only looked at radiant exposure in Florida and in Central Europe yeah about doubling
H what’s going on here example number three also on paints this test method is actually the same as in the previous example except that they had more frequent cycling here with a 17 minute light three minute light this water spray a simple one six fraction of the more common
1028 cycle in the previous slide this time the acceleration rate compared to Florida was 50% faster than the previous example but still over twice as fast as the example in the first Slide the automotive paint and the 4X acceleration H again and here one of my favorites these
Guys here have provided a very specific acceleration factor of 4.3 for the auto weathering specific to El Paso in Texas which is the town in western Texas and right on the border between us and Mexico El Paso has a transitional climate between a cold desert climate and the hot desert climate with hot
Summers usually little humidity and Mild dry Winters the acceleration here Falls in that 4 to 6X range predicted by R exposure equivalence since these geotextile materials that you see here on the picture they are usually dark they would be close to the black panel temperature and in the dry climate probably not very
Sensitive to moisture the fact that these materials are polyol based polymers also means there are they are relatively moisture insensitive so in this case the UV radiant energy dose is probably the major degradation factor and this would be consistent with the data but the widely varying and sometimes surprising acceleration
Factors in some of the previous slides says there is something more to degradation and acceleration that just radiant energy this may be due to temperature or moisture effect or even something else maybe trivial for some of you but it is it makes a lot of sense to look at these data
Um to get a free and clear and fresh mind from the previous examples we can see that first the experimental acceleration factors can differ significantly from those calculated from radiant energy equivalence and time comparion in the lab exposures second there is no Universal acceleration Factor the factors are highly specific
For both change in property measured as well as the material chemistry and also for the specific Auto and accelerated test used as I told you before if you only do quick calculations based on rant exposure you neglect the material in total and the material is the key factor um you’re interested in
When you’re doing the gradation study true acceleration factors must repeat that must be experimentally determined by using the outdoor and accelerated test data for the specific materials and the specific Laboratory test and the specific autolocation with this a specific sample tilt and orientation etc etc this means you need the Real Time
Auto exposures and climate interest to determine acceleration factors always do outdoor exposures to complement your laboratory with always these are just values real acceleration factors and calculate so here’s a list of average Auto anual rated exposure values just for your re reference and the associated exposure times in hours here in the
Instrument if it runs at 60 watt per square meter with no dark pH and these are the time factors or acceler eration factors you can calculate from that with all due disclaimers and cautions Etc so the maximum acceleration you can reach by compressing the radiation time is limited below
10 what if you don’t have time for that can’t you accelerate more h H yes you can you can by intensification and here you have a couple of options I will go through all of those or most of those um as listed here below let’s first look um what intensification
Means it’s through overstress that is in increasing a stress parameter such as solar Radiance in this case here or temperature to higher levels than what would occur Outdoors what this means is that rather than conducting a test at near maximum or maximum levels you run at higher than maximum levels one
Example of this type of acceleration would be the frel reflecting devices in Phoenix Arizona we call them M aqua where we use highly reflective mirrors to focus several Suns Sun equivalents onto one single Target board at least in the UV and low wavelength visible range um and this is a very established
Method and works quite well of course it is also possible to both accelerate through time compression as well as through overstress of course you eliminate nights and dark times and you overstress and then you get um even more acceleration modern Zar instruments and also through resen devices do have the
Ability and various test methods take advantage of that and allow irradiance higher than maximum IR Radiance usually up to three Sun level which is 180 wat per square meter in the UV between 3 and 400 NM just realize that there are practic as well as scientific limits to
The amount of overstress we can use without affecting the correlation the same is true with time compression by eliminating chemical processes that occur in the dark as well as eliminating temperature cycling and its effect so be careful the higher the acceleration Factor the higher the risk for non-correlation well take this chicken
Egg for example many of you may know that uh if I take that egg and expose it for 21 days under a mother hand at a temperature of 37° C at the end of that time I’ll have a baby chick but if I try to accelerate by exposing the EO about 4
Minutes at 175° cus H theide is not what you expect and this is exactly the same with your samples so what can I do what can you do well let’s look at each of the three primary weather factors in terms of the radiation we may think of exposing the
Material to Shorter wavelengths of higher energy U radiation we have covered this in detail in other webinars but we now see again that this is a very very bad idea intensification by higher energy radiation UVB UVB 3 30 bulbs as used in fluorescent UV devices were the original
LMS used for those exposures these this this States back to an earlier testing philosophy that if a material passes this test sometimes referred to as the bigger Hammer approach it could not fail in normal sunlight but this is past however one must be careful about the possibility of
Unnatural degradation in some cases the photochemistry can be so altered that the product passes the test but fades in normal sunlight this happens with the first or happened with the first Automotive Base called clear coat paint system failur a very expensive learning experience the primary fluorescent UV
Standards as shown in blue here at the bottom 4892 hmg1 151 these are the general standards and 154 and 4892 Parts 3 ISO 16474 Parts 3 for pains and coins these are the fluorescent standards um they specifically caution that UVB 330 lamps should not be used for weathering purposes you see the 340
Lamp here is much better in the Solar cuton region than the unrealistic radiation 33 yeah so that you believe that let’s have a look at an example in the graph on the left the Florida exposure shows that um material B is the red one um shows a greater change in optical
Density than material a in blue and this same change was essentially replicated in properly filtered cenon Arc here it looks very similar but look at the time this is 20,000 hours this is 4,000 hours this is an accelerated test but the weathering behavior of these uh of this PVC here is very
Similar between materials A and B and now look at the data from th rescent UVB what you see is there’s a reversal in ranking when exposing the material to UVB fluorescent UV in short do different tests than daylight get the different result another example here um is a comparison um of UV flu
313 with a low wavelength UV and the more realistic 340 nanometer length which I just showed you is a much better approximation of the solar cuton region um it’s for outdoor for Delta e um color change the green one here um of nine formulations of polyester
Coatings note that this is not a Time series it’s not 1 2 3 for 5 hours it’s not a Time curve these are the different samples sample number 5743 6219 eight of these Brown um polyester Coatings different polyester Coatings with brown color and they are in order of stability
Yeah moving from left to right the Coatings are de in decreasing performance so these are the best and these are the worst because this is the past fail line here Delta e past fail line and you see they are these these samples are in order of their
Performance the outo data is green the UVA 340 is blue and the UVB 313 high energy low wavelength Photon UV fluorescent length is in um in Violet here in pink and now look at the data only coding number one produces the same magnitude of change the UVB 3113 lenss in
Pink produces completely different rankings and magnitudes the two worst performing Coatings in the outdoor these two here they are actually the best in the UV b313 test these two that’s not good also quotings number four and six or and six which were very good performers Outdoors here you see allo good
Performers they are ranked being the worst in the UVB 33 test I think that should do it yeah for UV florescent I think you get my point don’t use3 tests if you don’t really very well know what you are doing for certain tests that may work well but you need to
Know what you are doing not only in flues but also in cenon instruments filter systems are available that provide lower wavelength radiation than existing in solar UV Radiance on Earth surface the key example is the so-called extended UV filter system specified Automotive standards some of you probably know EJ
2527 that was formerly SJ 1960 even the historically and still most frequently used cenon daylight filter system borrow borrow it’s Bor silicate Bor silicate inner and outou filters ineter that’s what that means provides a small amount of high energy photons not present in sunlight which may cause differences in photochemical response for sensitive
Materials but here you have the extended which is a completely different world this is from a study where the BASF reference clear code was used in a c instrument to assess differences in UV cuton what the researchers did they used different UV cut on filters and um and
Research the crack formation the crack formation appeared at different times using the same moisture cycle for the different cuton filters one two three and four when filters with a short u cut on employed the cracking appeared rather quickly whereas it took longer for cracking to form when longer w ref
Filters were employed maybe trivial but in practice this is sometimes not taken seriously enough a few years ago or many years ago I I should say the Consortium started to optimize the US cut on for Laboratory Testing the result was what we call Right light or called right light back
Then right light filter system which has been introduced into sdmd 7968 the the standard on Transportation codings both filter system Right light and the um Legacy filter system Right light is here into that Corridor these are the the extended ones this is the Legacy borrow borrow so both Rite and Legacy are
Currently specified by isone hm now new terminology is daylight type one for the Legacy system and daylight type two for the bright light we have a block on our website and fan file one of my colleagues who is one of the yeah let’s say the most experienced expert in in bettering
Applications in our company he wrote a short blog article on it just check that out he explained he’s explaining the status the slide here shows Preparatory research to hdmd 7968 uh done by mainly by Ford supported by atlas of course with the m Aqua Etc and the
Instrument um and that was presented by Mark Nichols of Ford in 2008 at the atca the atlas technical conference on accelerated aging and invation in Oxford UK it’s quite old but that was the the kickoff of development of acmd 70 7968 accumulation of photooxidation products it’s shown
Here um ratio with pass FD and outdoor and accelerated weathering were the basis of that I don’t I don’t go into specifics this paper explains that there’s also more published on that these these infrared bands they change with weathering and if you determine the ratio of different bands here AB versus
CD you get an indication about uh the progress of weaing let’s now have a look into the level of spectral Radiance many standards actually allow High Radiance level as I said already increasing the radiance level is a common method we do this already with the Fel reflecting devices M AAR or
Accelerated mrest devices described in part two of our webinar series on fundamentals of just close the door but running tests at both increased IR Radiance and increased temperature however is quite uncommon the reason being that is generally leads to poor correlation as we start to throw the Natural Balance of
The stress factors out of normal so with r Radiance intensification we now need to talk a little bit more about the law of rocity but I don’t really like law law is not good I I like better principle or concept law is it’s too absolute it’s a principle or
Concept um this principle of reciprocity refers to running a test with higher Radiance than normal or endus than normal conditions or endu conditions for a shorter time but to the same radiant exposure of a natural exposure at normal Radiance for for a longer period of time in asking are the
Results the same to put it simply can I get the same result in half the time by exposing my material to twice irance or in the third of the time with three times the irance ETC or even simpler in even simpler words do two photons of the
Same energy to exactly twice damage than one Photon usually the law or the principle concept of reciprocity is reasonably valid for the photochemical initiation if other parameters like temperature are reasonable however the degree of this reasonableness varies as strict rocity oance is usually the exception and this can result from several factors while
Photons initiate photochemical degradation much of the damage actually results from secondary reactions usually involving free radicals and these reactions are mostly driven by temperature and not by photons Moisture Control can become difficult especially at high Radiance levels which can affect specimen temperature moisture absorption dision rate also oxygen diffusion and
Availability in the sample Matrix is a key factor in determining polymeric ration and this cannot be accelerated adequately and there are some dark time reac sometimes for certain polymers that can’t be photo accelerated these are only some of the reasons why rocity mostly doesn’t hold true
But there is a technical way to find out if it works or not is technical specification 19022 defin the process by which reciprocity can be validated it’s a relatively simple for step process first test at lowest Radiance level then test at increased Radiance levels here you see 5587 100 540 different Radiance
Levels then plot the test results as a function of radiant exposure and not as a function of time and then all these points fall together to one straight line in this case here calculate the deviations from a fit of the data meaning determine the pier and correlation coefficient and
As you see here it’s excellent can’t be better piercing correlation coefficient is excellent so for this material for the Orit orange weathering uh reference material here from um it’s it’s a specific reference material in CEST Alpha that study show showed that for this material it worked very well another example a bright yellow
Textile for safety Gars this time two Radiance levs were used at 1X 42 and 2x 84 wat per square met again when the color change was plotted against radiant exposure the reciprocity was very good as shown by the linearity of the the same procedure also works for materials where the property change does
Not linearly depend on time and weight and exposure it doesn’t have to be a linear curve this is demonstrated in a study of two poid thingses pu1 blue a foam and pu2 pink a v fabric with a with a V fabric behind exposed in a c Alpha at
Different Rance levels according to ISO 105 P6 the so-called hot light fastness test that doesn’t have any rain cyc in you see it also works well you put these this is time if you plot that to rain exposure in the UV you also get these not into a straight line but into one
Curve that you can fix um fit that you can fit here’s a fourth example this time for two different types of automotive interior textiles test one uses the relatively normal Radiance level of 47 per square meter yeah and test two three times the radiance 141 wat per square
Meter as you can see from the graph the rocity was quite good now one thing to note here my parameter of interest in all these cases was color change which is primarily a result of photochemical reaction which destroys the colorant and these reactions tend to primarily primarily be Photon dependent
When you get into physical parameters such as cracking adhesion loss or tensile strength which are often a combination of UV exposure combined with temperature and or moisture cycling the law of reciprocity likely will not be followed quite as well because there are a lot of non Photon reactions occurring in poly
Medication important to keep in mind the law of reciprocity may not always be valid here is an example for that showing that diffusion may play a major role and distort reciprocity we have oxygen and we have air which nitrogen plus oxygen and we get completely different um um to completely different uh curves
Here that was increase the radiance now let’s have a look at temperature for temperatures we can possibly raise the temperature to higher levels in an effort to increase degradation rates especially for physical degradation mechanisms we can run tests that employ temperature cycling a rule of suum in basic chemistry class is that reaction
Rate doubles for 10° celius rise in temperature rule of some however that only applies to some specific chemistry in Solutions and is not true for the solid state materials we mostly deal with the rule is derived from the more General equation the K is the rate of the chemical
Reaction what is shown here is not the arous equation what is shown here is what we call the modified arous equation with an IR Radiance Factor where the alpha the exponent Alpha characterizes the um characterizes the reciprocity if it is one the law of reciprocity is it’s a material specific
Coefficient I won’t go into details of that this is uh this is topic of other webinars but I want to point out that there are two important terms here regarding the rate of chemical reaction the first the activation energy EA EA activation energy um so circuit in
Red this is the energy that must be put into the system for a chemical reaction to occur because you have to go over that energy Mountain like needing a spark to ignite an explosive which is nothing else than a rapid oxidation reaction the second is the temperature circuit in blue with
Slow activation barriers there are many molecular molecules with enough energy to overcome this barrier so the reaction is going fast anyway and an increase in temperature has a small effect an increase in temperature increases the amount of molecules with higher energy translation energy or vibration energy more molecules are able to overcome
Higher activation barriers thus this has a big effect on reactions with high ination energies this is not an onoff mechanism of course it is related to the probability distribution of a molecule having a high enough energy to react but that’s an advanced topic only a little bit on that here you have this
Distribution all but purely photolytic or Photon dependent reor rates increase with temperature the activation energy is a material dependent property it is the amount of energy this must be put I mentioned that already um to overcome this barrier and a high activation energy not many molecules this is a high activation energy not
Many molecules have enough energy to react if the activation energy is lower then you have a bigger portion of molecules that uh have the um enough kinetic energy and then if you change the temperature here you can actually influence that a lot this is a new temperature tempature distribution for a higher temperature
T2 but I do not want to go too much into detail here there’s a some activation energies Delta T’s here these are activation energies plotted and this is gloss loss and here photo oxidation um that would a little little bit too far I go into too much detail here it can change dramatically
With activation energy this is the message here not all ranking reversals are the result of Po sunlight simulation as discussed in in the last paragraph the reaction rate of photochemical degradation processes depends on a number of different factors including effective Radiance and temperature and the particular material sensitivity to
The radience and temperature and finally the property change here we see the influence of temperature and degradation rates of different materials note this graph in that the exposure of three different texile fibers was conducted with fluorescent du V length at 30 Celsius and 30 relative humidity and here you have the same at
60 Celsius and 30% relative humidity you see reversal of ranking just due to increase of temperature now we combine the acceleration factor with the modified aous equation and get this nice formula that we are using a lot in modeling this is the acceleration factor which is the acceleration factor
Is a product of two independent acceleration factors one regarding temperature one regarding radiation R here is radiation um and here you have the uh the radiation and the temperature terms which is the quot um the the ratio of the chemical reaction rates uh and this simple product here is um is caused by
Actually if you go down into specifics by the Fronton principle actually which says that um the photo photo chemic photo physical steps are independent from temperature because they are running on completely different time scales and translation vibration seems to be Frozen when you are looking at a
Transition of energy in in the um in the electronic states of the molecule other um energy levels depending on reference temperature material properties the theoretical acceleration Factor can significant can vary between different exposures incorrect estimation of sample temperature can lead to misinterpretation measuring the correct sample temperature should facilitate the comparison between different
Exposure another reason why conducting tests at higher than maximum endu temperature can be a problem is the fact that the material may approach the range of the glass transition temperature this is the temperature where where polymer changes from a hard glassy state to more rubbery State both states have different
Physical properties and therefore weathering behaviors different diffusion coefficients migrations different etc etc the problem is that for some polymers especially quoting the TG of these systems is often comined near the typical black panel or specimen temperatures and this can lead to erroneous interpretation degradation grades if you are not aware of that this
Is just examples of different glass transition temperatures taken from the PVC handbook here from um from the literature 20 to 30 years ago clear codes based on acrylic melamin systems were very popular and these systems showed weaknesses in cracking behavior and stability against acids this weathering study here shows that degradation of acrylic
Melamin Coatings is six times higher at 80 celus then at 7 celsius instead of the rule of sum of two at 80 Celsius only one six of the UV R energy is required with 25% gloss loss than at 70% reason the TG is between 70 and 80 for acrylic urethane system this is
Different they are reacting slower 1.4 than the rule of sum of two mind TG well this can be very important for temperature we can raise the temperature to higher levels but we also can employ cycling according to the coffing Manson model the thermomechanical degradation processes are based on the amplitude of
The applied stresses which here means the temperature range of th cycling Delta a uh ta and Delta Tu a is accelerated U is in use environment and these are the number of Cycles to failure the Norris lansburg model estimates an acceleration Factor AF Norris lansburg by multiplying the con confin an
Amplitude with a frequency term and the arenus temperature term with temperature max in both uh environments accelerated and and use this slide deck here that you will be um sent uh that you will get includes two more slides showing an application in the calculation example but this
Would be too would would lead too far for today for this this one hour presentation here so I leave it out here I just wanted to mention the names no lansburg and coffein Manson and those of you who are interested in that um just Google it Wikipedia probably gives you
Enough information to get a good idea if you want to dive deeper then you can make a scientific Lit Literature on that as well or textbooks now let’s have look at moisture what can I do with moisture well um as I already mentioned the first generation of clear codes 20 to 30 years
Ago were based on acrylic M systems investigations of clear Cod systems were particularly important back then because they had weaknesses first and foremost cracking but also acid resistance weathering test methods were developed 20 to 30 years ago first only in a climate chamber with water without irradiance theoretically cracks are
Generated when the humidity cycle has such a large amplitude to exceed the tensile strength after a certain point here in the trial um is it is not reached in this one here yeah this amplitude is not enough no cracks as expected but now the amplitude is increased the acrylic melamin systems
Crack after 2,000 hours water penetrates deeper the tension is higher than tenside strength formation of cracks is observed the consequences for the pain man manufacturer de then was development of clear code systems with lower TGs and higher tenside strengths why higher tensile strength to stay out of the
Critical conditions and lower TG at about 20 cus um to compensate mechanical tensions by swelling and contraction in the rubbery state above the T the glass transition temperature which also avoids cracks modern 2K P systems are very good in this respect plus acid resistant P groups avoid damage by acid rain
So here are some of the big takeaways from this seminar most standards are based on time compersion and use parameters within natural limits a compromise must be made between correlation acceleration The Closer To Nature the more likely it will correlate for intensification careful consider test conditions and material specific sensitivities
No blackbox approach look at the materials if you’re doing intensification options for intensification short wavelength radiation typically does not work increased IR Radiance can work if flow of reciprocity applies and increased temperature can work if the glass transition temperature allows so um you should be always above or below you
Should not cross it or you should not have a different class a different state in test than in Outdoors no I I hope you got that message on these slides acceleration factor of 10 or higher are extremely material and environment specific be careful be very careful okay I’m coming close to the end
Of today that was acceleration the next next will be correlation um I’m not sure this will be presented this week next week I’m not 100% sure you should check out our calendar here is the um overview about our knowledge resources check out the knowledge Center on the atas website we
Have a Blog here atas weaing blog calendars three calendars also of trade shows but also on on future seminars we have technical guides technical documents a library ordered by topics like textile codings technology standards Etc we have recorded online seminars huge huge list of them we have weather summary reports that you can
Download for free so this is a pleora of knowledge um of a knowledge resource for bettering this is just upcoming online seminars right now we are some I’m not sure where we are this is maybe September this are old dates I’m sorry uh but the calendar looks like that for
Until March April you can you can check that out and also the emails you get with the direct registration links and with this I would thank you for your attention I will have a brief look if there are questions yes how to choose one question how to
Choose between UVA 340 UVA 351 lmbs to study the degradation of microplastic p p p p yeah I have to tell you that UVA 340 is a good approximation of the solar cut on region so the solar low wavelength region Outdoors UVA 3501 lamps simulate the cuton region of solar
Radiation through window glass so inside cars or inside houses so this is the difference between UVA 340 and UVA 351 the UVA 351 lamp has not really uh succeeded it is a it is a good lamp but uh most test are done with solar radiation outdo simulation but only in
The um in the lower wavelength UV radiation no visible and no infrared it’s still through as Tov but this is the difference so if you are looking at outdoor conditions uh you have to use the UV h40 if you are looking at behind window glass you have to use the UV 351
L so I don’t see any more questions let me see no I don’t see any more questions so with this I think we are right in time 2 minutes after the hour thank you very much uh for uh participate participating uh I hope it was a little
Bit interesting for you you will get the slide deck and if you have followup questions please go ahead and send us a message and somebody will come thank you very much and have a great day have a great evening have a great night and stay safe and well and healthy goodbye