Multi-irradiance photoaging chamber

Abstract

Multi-irradiance photoaging chamber. Chamber (5) for studying the photoaging of samples, the chamber comprising: - a support (15) having at least two study zones (Z1, Z2, Z3) spaced apart from each other and each having at least one sample holder to receive at least one sample to be studied, - a light source (10) configured to illuminate the study zones (Z) and having at least one light-emitting diode lamp (30), - a study chamber (20) in which the support is housed, the chamber being configured so that, in each study zone, the irradiance of the radiation emitted by the light source is homogeneous and so that the study zones have different irradiances of said radiation. Figure for the abbreviation: Figure 1

Description

Description Title of the invention: Multi-photoaging chamber irradiance

[0001] — The present invention relates to the field of the study of photoaging of materials, and in particular that of enclosures intended for such a study.

[0002] — Photoaging of a material is the degradation of its properties under the effect of prolonged irradiation by light radiation, particularly in Ultraviolet (UV). The properties that degrade are, for example, mechanical (loss or increase in the modulus of elasticity, damage, cracking), optics (color change, opacification) or electrical (conductivity).

[0003] EP 2 682 737 A1 is known to have an aging chamber comprising a A set of UV-emitting light-emitting diodes (LEDs) that radiate homogeneous distribution of the samples housed within the chamber. In order to obtain a homo- homogeneity of the intensity of UV radiation illuminating all samples in the study area, the emissions from each of the LEDs are coupled in such a way that the spectral emission range is broadened. Another example of this type of enclosure This type is described in EP 1 528 388 B1. Such speakers are particularly good adapted to compare the aging of samples made of different materials or to test several identical samples subjected to different lighting conditions identical.

[0004] — They are notably used to study the behavior of materials forming photovoltaic modules. However, in practice, irradiance levels to which such photovoltaic modules are subjected can vary in such a way significant depending on the location, placement and orientation of the photo module Voltaic in relation to the sun.

[0005] — There is therefore a need to quickly test a material under different conditions lighting conditions.

[0006] — The invention aims to satisfy this need and proposes an enclosure for the study of photo- sample aging, the chamber comprising: - a support presenting at least two study areas spaced apart from each other and each comprising at least one sample holder to receive at least one sample to be studied, - a light source configured to illuminate the study areas and comprising at minus a light-emitting diode lamp, - a study room in which the support is housed,

[0007] — the enclosure being configured so that, in each study area, the irradiance of the radiation emitted by the light source is homogeneous and so that the study areas have different irradiances of said radiation. The invention thus makes it possible to study, within the same chamber, the aging of samples, for example, made of the same material, under different irradiance conditions. The inventors have departed from the prior art design principles for chambers, which aim for homogeneity of irradiance across the entire illuminated area, a simpler approach than determining separate, homogeneous irradiance zones as described in the invention. In other words, as will become clear later, the invention takes advantage of the well-known spatial inhomogeneity of the radiation emitted by at least one light-emitting diode lamp, whereas the prior art sought to overcome this inhomogeneity. A "light-emitting diode lamp" or "LED lamp" contains one or more light-emitting diodes. An LED lamp offers the advantage of spatially delimiting and temporally maintaining study areas, which is practically impossible with a xenon or mercury lamp. The "irradiance" of a light radiation is the power of the radiation per unit area perpendicular to the axis of emission of the radiation. A study area exhibiting homogeneous irradiance is such that, among a set of at least two measurement points evenly distributed across the study area, the ratio between the largest absolute difference between the irradiance measured at one of the measurement points and the arithmetic mean of the irradiance measured across all measurement points, divided by said arithmetic mean, is less than 10%. Advantageously, samples placed within the study areas can thus be tested in accordance with ISO 4892-1 of July 2016. Preferably, the area covered by each study zone includes a rectangle with a length of at least 1.5 cm and a width of at least 0.75 cm. In this way, the enclosure is suitable for conducting tests in accordance with ISO 4892-1. Preferably, the surface area of ​​each of the study zones is greater than or equal to 1 cn?, preferably greater than or equal to 2.5 cm?, It may be less than or equal to 150000 cm?, or even less than or equal to 6 cm?, Such an area allows the aging of a sufficiently large sample to be studied, as the evolution under irradiation of certain properties of the material constituting the sample can only be characterized on samples of a minimum size. In particular, to ensure good reproducibility of measurements, the study areas preferably have a width between 7.5 mm and 80 mm. The study areas are separated from each other by a distance which, preferably, is at most 32.5 mm. The study areas can each have a varied general shape, for example, polygonal, elliptical, or circular. Preferably, at least one, or even all, of the study areas have a general rectangular shape, which is the most suitable. The study areas can be delineated on the support. In particular, the support may include a marking, for example a line or a printed mark, that delineates the perimeter of the study area. Alternatively, the support may have recesses, the outline of each recess defining the perimeter of a corresponding study area. According to yet another variation, the outline of the sample holder may delineate the extent of the study area. At least one, in particular each, of the sample holders can be shaped so that the sample is fixed to the sample holder, for example by snapping. The lamps can be arranged, notably regularly, around a central axis and can illuminate the support, each along an emission axis parallel to the central axis. Preferably, the study areas are arranged so that, under the effect of illumination by the lamps, the study area receiving high irradiance is positioned closer to the central axis than the study area receiving lower irradiance. Preferably, the face of the support intended to be illuminated by the lamps is flat. Preferably, at least one LED lamp has an emission spectrum with wavelengths between 200 nm and 2000 nm. Preferably, it has an emission spectrum with wavelengths between 290 nm and 420 nm. Advantageously, unlike, for example, filtered xenon lamps, an LED lamp with such a narrow spectral range allows for effective temperature control of the samples. The irradiance on the radiation support that the LED lamp is capable of emitting can be distributed around the axis of the LED lamp according to a Gaussian distribution. Preferably, the enclosure includes several LED lamps. Preferably, the number of LED lamps is between 1 and 100. A high number of lamps facilitates the delimitation of study areas, and increases the homogeneity of irradiance over them. LED lamps can be supported by a base with a surface density on the base of between 0.01 cm² and 1 cm³. Preferably, the base has a face parallel to the face of the support on which the study areas are defined, the lamps being arranged, in particular fixed, on said face of the base. Preferably, the emission axis of the LED lamp is perpendicular to the support. Preferably, LED lamps have the same emission spectrum. Thus, the The temperature in the study areas is identical, as is the spectral distribution of the radiation. It is therefore possible to separate the effect of irradiance on the sample from that of temperature and spectral distribution. Furthermore, the lamps can emit the same light intensity. In one variant, the light source comprises two types of LED lamps with different emission spectra. Specifically, lamps of the first type can be arranged on one section of the base, and lamps of the second type on the other. In this way, the support can present study areas with different irradiances at different wavelengths. Preferably, the light source includes a base supporting the LED lamps which are arranged regularly on the base in an elementary square, hexagonal or triangular pattern, preferably square. The LED lamps can be removed from the base. This makes it easy to study the effect of exposure to radiation from different spectral ranges. LED lamps can be separated by a distance of less than or equal to 10 cm. At least one, preferably each of the LED lamps can be arranged so as to illuminate the support along an axis perpendicular to the support. Preferably, the enclosure is configured so that the irradiance difference between two study areas is greater than or equal to 3 W / m², or even greater than 5 W / m², for example 7 W / m². The enclosure may include at least three study areas exhibiting different irradiances under illumination. Preferably, the chamber includes a heating element to heat the support, in order to test the cumulative effect of temperature and irradiance on sample aging. In particular, the heating element can be configured to maintain at least a portion of the support at a constant temperature. The heating element is preferably a resistive heating element or a Peltier module. It can be positioned opposite the face of the support on which the study areas are defined. Preferably, the support comprises first and second portions made respectively of different first and second materials, with at least one study area being defined in each of the first and second portions. Preferably, the first and second materials have different thermal conductivities. In this way, the first and second portions can have different temperatures by heating the support. The support may consist of more than two parts, for example at least four portions made of different materials, Preferably, so that the luminous flux reaching the portions is distributed identically over the portions, the portions are preferably distributed regularly around the central axis. Preferably, at least two study areas are defined in the first portion so as to present different irradiances under illumination by at least one lamp and at least two study areas are defined in the second portion so as to present different irradiances under illumination by at least one lamp and preferably so as to present identical irradiances to the corresponding study areas in the first area. Furthermore, the support can be movable relative to the LED lamp(s), specifically the distance between the LED lamp(s) and the support can be adjusted. Thus, the distance between the lamp(s) and the support can be adjusted to better define the study areas and / or to modify their distribution on the support and / or to modify the irradiance in at least one of the study areas. The study room preferably has walls that are opaque to visible and ultraviolet radiation, and in particular to radiation emitted by lamps. The light source can be placed inside the study chamber. Alternatively, the study chamber can have an opening, and the light source is positioned to illuminate the support through the opening. The invention will be better understood upon reading the detailed description that follows and the attached drawing in which: [Fig.1] schematically represents, in a lateral and cross-sectional view a) and a top view b), part of an example of an enclosure according to the invention, [Fig.2] and [Fig.3] schematically illustrate an example of a method implemented to delimit study areas of an enclosure according to the invention, [Fig. 4] schematically illustrates a light source in an example of an enclosure according to the invention, [Fig. 5] schematically represents different study areas of an enclosure according to another embodiment of the invention, [Fig. 6] is a photograph of an enclosure according to an example of an embodiment of the invention, [Fig.7] is a photograph of the enclosure support of [Fig.6], and [Fig.8] represents a map of irradiance over the study areas of the support of [Fig.7]. Figure 1 schematically and partially illustrates an example of a photoaging chamber 5 according to the invention. The enclosure 5 includes a light source 10, a support 15 and a chamber study 20 in which the support and the light source are arranged. The light source comprises a base 25 and sixteen light-emitting diode (LED) lamps 30 arranged on the base in a 4x4 square array. This number of lamps and this arrangement are not limiting. In another example not shown, the light source may comprise 25 LED lamps arranged in a 5x5 square array. In [Fig. 1], the light source is shown with a dashed line for clarity. This number of lamps is not limiting. The LED lamps emit identical radiation, that is, they have the same emission spectrum and the same luminous intensity. The support 15 is flat and the lamps are arranged on the base so as to emit light perpendicularly to the support along respective emission axes. When the support is illuminated by the lamps, the radiation R, shown by dotted lines, emitted by the lamps interacts. Thus, the irradiance in a zone of the support Z, located near the X-axis passing through the center C of the base and perpendicular to the support 15, is higher than the irradiance measured in a zone Z3 of the support far from said axis. The irradiance in zone Z3 is indeed lower because the number of lamps interacting near the edges of the square they form is smaller. Measuring the surface irradiance of the substrate allows us to define zones Z1, Z2, and Za in which the irradiance is homogeneous. Furthermore, since the LED lamps are identical, the substrate temperature and the spectral distribution of the radiation are identical in the different study zones, making it possible to investigate the effect of irradiance alone on the aging of samples placed in zones Z1 to Za. Figures 2 and 3 schematically illustrate an example of a method implemented to delimit study areas of an enclosure according to the invention. In the example illustrated in [Fig.2], the enclosure includes a single LED lamp 30 fixed on a base 25 parallel to the support 15. The support 15 is at an adjustable distance d from the LED lamp. The LED lamp is characterized by an emission spectrum of wavelengths, an emission axis Y of the light radiation, a beam angle θ of the light radiation, and an emission power P of the light radiation. Thus, the light radiation emitted by the LED lamp irradiates a surface S on the support, the area of ​​which depends on the beam angle θ of the LED lamp and the distance d between the support 15 and the LED lamp 30. Furthermore, an LED lamp emits light radiation at the beam angle θ, according to its own specific angular distribution. This angular distribution induces a spatial distribution of the irradiance I of the light radiation which generally follows a Gaussian shape whose maximum La is on the emission axis of the LED lamp. As illustrated by comparison of figures 2 a) and 2 b), the further the LED lamp is from the support, the more the irradiance I decreases because the illuminated surface S of the support increases for the same emission power P. In addition, the closer the LED lamp is to the support, the greater the local variation in irradiance. As illustrated in [Fig. 2] a), for at least a distance d between the LED lamp and the substrate, at least two study areas Z1 and Z2 can be defined, in each of which the irradiance varies by less than 10%. Thus, knowing the characteristics of an LED lamp described above, a person skilled in the art can routinely delineate study areas on the substrate and vice versa. Furthermore, they can easily measure the irradiance and the spatial variation of the irradiance using a radiometer adapted to the emission spectrum of LEDs. The example shown in [Fig. 3] differs from that shown in [Fig. 2] in that the enclosure contains two LED lamps identical to the one shown in [Fig. 2], spaced apart by a distance e. This figure illustrates the influence of the distance e on the delimitation of the study areas. In the example shown in [Fig. 3] a), the distance e is such that, on the surface Sc of the support illuminated jointly by the two lamps, the sums of the irradiances I, each distributed Gaussianly, allow the delimitation of study areas Z1 in which the irradiance is homogeneous. In [Fig. 3] b), due to a larger distance e, the study area Z1 is smaller and has a lower irradiance.The representation illustrated in figures 2 and 3 is schematic, and a person skilled in the art knows how to refine the delimitation of the study areas, for example by numerical simulation using an optical calculation tool such as the TracePro® software marketed by Lambda Research Corporation. According to one variant, the light source may comprise two types of LED lamps 30 that emit according to different spectra and optionally with different intensities. In particular, it may comprise an equal number of lamps of the first type and lamps of the second type. For example, the lamps of the first and second types may form first T and second T groups, in which the lamps 30 are distributed identically and are symmetrical with respect to each other. For example, as illustrated in [Fig. 4], the lamps of the first group and the second group emit according to spectral ranges A, and A, Figure 5 illustrates an example of the distribution of study areas on a support illuminated by the light source of Figure 4. On the portion of support 15 superimposed on the lamps of the first set T, study areas Z1(A1) to Z3(A1) are formed, exhibiting an irradiance (I2(A1) > I3(A4)) in a spectral range A, which increases at as one approaches the center of the set of lamps in the first group. The same applies to the portion of the support superimposed on the lamps of the second type, except that the spectral range of the radiation there is equal to A. The portion 50 of the support that is superimposed on the adjacent lamps of sets T1 and T2 is subject to the interaction of radiations with spectral ranges A and \,, so that three other study areas exhibiting different irradiances can be defined. Furthermore, in order to study the combined effect of irradiance and temperature on photoaging, the enclosure may include, as illustrated in [Fig.6] a heating means 55, for example a resistive heating plate, to heat the support. In this example, the support 15 and the resistive heating plate are arranged in the study chamber 20. The light source 10 comprises twenty-five LED lamps emitting in the UV range at a wavelength of 305 nm. It is positioned outside the study chamber and can emit radiation through an opening 60 in an opaque wall of the chamber. The support is also positioned between the resistive heating plate and the light source. The resistive heating plate thus heats the face of the support opposite to the one intended to be illuminated by the light source. Furthermore, in order to evaluate the effect of temperature on photoaging within the same chamber, as illustrated in [Fig. 7], the support comprises four sections 70 made of different materials, preferably with different thermal conductivities, on which study zones Z1 to Z3 are defined to receive different irradiances. In the illustrated example, the sections are made respectively of cardboard, Dibond®, aluminum, and a multilayer material composed of cardboard and aluminum sheets, and are distributed regularly around the central axis X of the light source. The study areas are rectangular, measuring 15 mm long and 45 mm wide. They are covered by sample holders of the same length and width. The sample holders also have tabs at each end to hold a sample. A test was carried out by heating the substrate uniformly from its underside and illuminating the opposite side of the substrate with the light source. The temperature on each portion of the substrate was measured, as well as the irradiance in each study area within the different portions. As shown in [Fig. 8], the chamber allows, on a single substrate, the study of the photoaging of a sample under the effect of the same irradiance (e.g., 27 W / m²) and at different temperatures (e.g., varying between 62 °C and 74 °C). It also allows the study of the photoaging of a sample at a given temperature (e.g., 62 °C) under the effect of different irradiances (e.g., 12 W / m?, 20 W / m? and 27 W / m°). The invention can thus be used in particular for the study of the photo-aging of polymer materials intended to be placed outdoors in daylight. The invention is obviously not limited to the examples of implementation described by way of illustration and not limitation.

Claims

Demands

1. Enclosure (5) for the study of the photo-vicillization of samples, the enclosure comprising: - a support (15) presenting at least two spaced study zones (Z) one from the other and each comprising at least one sample holder (75) to receive at least one sample for study, - a light source (10) to illuminate the study areas (Z) and comprising at least one (30) light-emitting diode lamp, - a study room (20) in which the support is housed, the enclosure being configured so that, in each study area, the irradiance of the radiation emitted by the light source is homogeneous and so that the study areas present similarities to each other. radiances of said radiation are different.

2. Enclosure according to claim 1, comprising a heating means (55) to heat the support, the heating means being preferably a resistive heating element or a Peltier module.

3. Enclosure according to any one of claims 1 and 2, comprising several light-emitting diode lamps.

4. Enclosure according to the preceding claim, the diode lamps electrolu- minescent being supported by a base with a surface density on the base between 0.01 em” and 1 cm”,

5. Enclosure according to any one of the preceding claims, the area the surface area of ​​each of the study areas being greater than or equal to 1 cm, preferably greater than or equal to 2.5 cm?

6. Enclosure according to any one of the preceding claims, the at minus a light-emitting diode lamp exhibiting a spectrum emission of wavelengths between 200 nm and 2000 nm, of Preference for 290 nm and 420 nm.

7. Enclosure according to any one of the preceding claims, comprising at least two light-emitting diode lamps having different emission spectra.

8. Enclosure according to any one of the preceding claims, the light source comprising a base supporting the lamps which are arranged regularly on the base according to a basic square pattern, hexagonal or triangular.

9. Enclosure according to any one of the preceding claims, the difference in irradiance between two study areas being greater than or equal to 3 W / m², or even greater than 5 W / m², for example 7 W / m².

10. Enclosure according to any one of the preceding claims, comprising at least three study areas showing under illumination different irradiances.

11. Enclosure according to any one of the preceding claims, the support comprising first and second portions (70) made res- respectively of different first and second materials, at least one study area being defined in each of the first and second portions.

12. Enclosure according to the preceding claim, the first and second materials having different thermal conductivities.

13. Enclosure according to any one of claims 11 and 12, at least two study areas being defined in the first portion so as to exhibit different irradiances under illumination by at least a lamp and at least two study areas being defined in the second portion so as to present different irradiances under illumination by at least one lamp and preferably in such a way as to exhibit irradiance identical to that of the corresponding study areas in the first zone.

14. Enclosure according to any one of the preceding claims, the The support is mobile relative to the lamps, particularly the distance The position between the lamps and the support is adjustable.