GB2064788A - Apparatus for testing the resistance of a specimen to light and weathering - Google Patents

Abstract

Light and weather resistance- testing apparatus with a testing space within a chamber which contains at least one gas discharge radiator S and reflector 2 and a selectively reflecting filter device for simulation of sunlight or similar radiation or climatic conditions. The specimens mounted on a carrier 3 are brought to a desired temperature profile or temperature gradient during the light and weather resistance- testing by gradually or zonally heating and/or cooling the specimen either directly or via the specimen carrier e.g. by heating coil Q1, cooling coil Q2 and cooling blower 7. <IMAGE>

Description

SPECIFICATION Apparatus for testing the resistance of a specimen to light and weathering The invention relates to a light and weather resistance-testing apparatus for examination of the influence of sunlight or other climatic conditions on material such as textiles, rubber, leather, plastics, varnish, paints and so on.

Devices of this type are described, for example, in our German Patent Specifications No. 1904097 and 2502239. Reference is specifically made to the disclosed contents of these Patent Specifications.

The samples or specimens to be tested are exposed in the apparatus to radiation and the other influencing quantities of weathering, such as heat/cold, atmospheric humidity/ water, harmful gases etc. In sufficiently stable specimens and varnish samples, which are normally applied to test plates, the specimens are directly inserted into the apparatus without a carrier. After to the exposure, the alteration in physical etc. properties of the specimen under test is defined by comparison, visually or according to measuring techniques, with a non-exposed specimen.

It is known that many decomposition processes are dependent on temperature. Therefore data on the temperature-dependence of the light and weathering resistance are valuable. Up to now such data could only be obtained by a series of experiments in which the specimens are exposed in turn to different temperatures. Besides, the entire apparatus or the testing space had also to be brought to the specimen temperature desired at any time so that the weathering test or the series of tests lasted some one hundred to one thousand hours if several temperatures had to be tested.

It is an object of the invention to ascertain the light and weathering resistance of organic materials as a function of the temperature of the specimen during an experiment.

The invention accordingly consists in apparatus for testing a specimen to ascertain its resistance to light and weather having a testing space within a chamber which contains at least one gas-discharge radiator and reflector and a selectively-reflecting filter device for simulation of sunlight or similar desired radiation or climatic conditions as well as specimen carriers or holders for elongated areal specimens, characterised by a device for the generation of a temperature gradient in the specimen.

Any and all combinations and sub-combinations of the described and represented features both together and in combination with features known per se, especially from German Patent Specifications No. 1904097 and 2502 239, also form part of the invention.

Modifications of the embodiments are of course possible without departing from the scope of the invention.

With the aid of the invention data is obtained on the temperature-dependence of the light and weathering resistance of a specimen in a single experiment. A calculation of the disintegration energy for the respective process is easily possible. If the specimens are placed on a good heat-conductive, preferably metallic sample carrier and, with long specimens, a definite but different heating or cooling is provided at both ends of the preferred rectangular specimen carrier, a linear temperature profile appears along the specimen carrier, and the specimen. This is true in any case for sufficiently thin samples which for example lie closely packed on the specimen carrier and are clamped, pressed against or similarly placed thereon. Thicker specimens, such as for example specimen test plates, can of course also be heated and/or cooled directly and separately as mentioned above.In any case it is no longer necessary to bring the entire testing space to the desired temperature. This is a very welcome advantage of the invention especially from the point of view of saving in energy.

The inventive principle of generation of a temperature gradient or temperature profile of the specimen either directly or indirectly with the aid of specimen carriers is not limited to specifically to be examined materials or properties. The simulated processes and effects leave behind, as a result, changes in the macroscopic, mechanical, thermic, electric and optical property such as, for example, mechanical strength, thermal conductivity, electrical conductivity, constant electricity transmission and colour of material, such as plastics, metals, non-metals, glass, ceramic, textiles with or without various coatings or preparations.

As the invention refers basically to the generation of a temperature gradient (temperature profile) linearly or non-linearly, it is also independent of the type of test apparatus or the test area i.e. how and where the test occurs under the desired conditions.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which show certain embodiments thereof by way of example and in which: Figure 1 schematically shows a first embodiment of apparatus for testing the resistance of a specimen to light and weathering, having a specimen carrier which is rectangular in plan view for holding a thin specimen, e.g.

foil or varnished paper or the like, with different heating or cooling at both ends for generation of a graphically represented linear temperature co-efficient over the length of the tested or observed area of the specimen.

Figure 2 shows a modified embodiment with electrical heating elements such as pipe heating elements or cartridges or sheets arranged directly in the specimen carrier, Figure 3 shows an embodiment with a heated foil which has a desired heating conductor sample or a desired distribution of electrically conducting parts such as graphite or carbon in plastic.

Figure 4 shows the side of the specimen carrier facing away from the radiation source or the weather, which is blown against by means of nozzle, from which a flow of liquid of varying temper flows, Figure 5 shows a specimen carrier which is tempered with Peltier elements adjusted to different temperatures, and Figure 6 shows an embodiment in which the specimens (suspended from carriers) are gradually moved in and out of a bath of a tempering medium.

Referring now to the drawings, as will be apparent from Fig. 1, the testing apparatus contains a radiation source in the form of at least one gas-discharge radiator S, and/or any other weathering devices, the radiation source preferably being arranged in a parabolic reflector 2, which is known per se. A selectively-rejecting filter device for simulation of sunlight is also provided as known per se but this has not been illustrated. The specimen carrier with the specimen placed on it closes the exit opening for the radiation on the reflector. The specimen may e.g. be drawn into the specimen carrier 3 by suction cups or openings 4 in the plate 3 to which suction pumps such as bellows or diaphragms or the like may be connected, and which are mounted below the plate 3.In the area of the end faces in the plate 3 are mounted pipes or hoses of helical or screw configuration, through which liquid such as, for example, a cooling liquid at Q1 and a heating liquid at Q2 or even a gaseous medium, brine or the like, may be passed either by direct connection to a main system and discharge (Fig. 1 right) ar enclosed cycle (Fig. 1 left) via pumps and/or storage units. The quantities of heat supplied are different, like the temperatures; in the embodiment, the heat quantity Q2 is supplied higher at the left hand of the specimen carrier 3 than at the right hand at Q1. The temperature is measured at different test points on the surface of the specimen carrier 3 facing the specimen and supplied to a temperature adjustment and evaluation device Tm.

On radiation in the test apparatus, the temperature of the specimen is increased by the energy absorption, the temperature profile of the specimen will, however, remain basically as is shown on the left in Fig. 1. Thus T1 is the starting temperature and T2 the end temperature, whilst Tm is the average temperature, Ts being the temperature increase by radiation.

To reduce the heat transfer a further cooling blower 7 is shown in the embodiment according to Fig. 1, which blower moves a broadly blowing cooling air stream across the specimen in the direction of the arrow 6. The air discharge is made at 8 through a slot. The specimen itself is not shown in Fig. 1.

In the embodiment according to Fig. 2 a specimen 9 having an appreciable area is clamped to its carrier 3 by means of clamps 11, preferably in the area of the two end faces of the longitudinally extended rectangular body. Otherwise the arrangement is basically that of Fig. 1.

In Fig. 3 a specimen carrier 3 is shown with, for example, an areal specimen 9 adhered thereto and heated foil 10 adhered therebeneath e.g. with plastic carrier, and heating element, conductor pattern or the like facing the specimen carrier according to desired heat distribution whether linear or nonlinear. The latter may also be obtained by different pigmentation or distribution of particles of graphite, carbon or the like in a plastics foil body.

In Fig. 4 the specimen 9 is pressed by means of pressure plates 1 2 into the area of the twe end face ends against the specimen carrier 3, the underside of which facing away from the specimen, being subjected to flowing liquid, hot or cold gas or liquid of different temperatures or amounts of heat so as to obtain linear or non-linear temperature flow over the length of the specimen and/or specimen carrier.

In Fig. 5 the specimen is wound on and off rollers for example in strip or similar form e.g.

by motors, said rollers being arranged before and after the specimen carrier 3 the specimen itself being in the closest possible contact with the facing surface of the carrier 3. On the underside of the specimen carriers 3 are arranged Peltier elements 1 3 of which, for example, the cold side of the right outer one faces the specimen carrier whereas (at Ql) the hot side of the Peltier element faces the specimen carrier 3 at the left side (at Q2). As in Fig. 2 several individual areas of different tempering i.e. heat input or heat output or created.

Whereas the preceding embodiments show horizontal arrangements the specimens and specimen carrier, in Fig. 6 a vertical arrangement of the specimens and, if necessary, also the specimen carrier is shown with another type of movement device without being limited thereto. The specimens, e.g. lacquered tin plates, stand or are suspended in containers on a turntable or plate and may be sunk into a tempering bath such as for example, a water bath and withdrawn again at controllable speed e.g. by a worm gear so that a desired temperature gradient may be aimed at during radiation by means of a simultaneously submerging radiator S and/or weathering.The specimens 9 are releasably attached in con tainers 14 to a turntable disc or a plate driven by an electric belt and dip at their other end slowly in or out of a bath 1 6 of a container 1 7. If necessary a rotary movement may also be generated with lateral flow of a fluid without a motor if the specimens are arranged on a rotary turntable 1 5 in the fashion of bucket ring of a turbine. If necessary also an upper simultaneously rotating plate 1 8 may further be provided. Modifications of the embodiment may also be made of course without departing from the scope of the invention. The individual features of the embodiments are exchangeable with each other as found desirable.

Other known beam sources particularly such as those referred to in German Patent Specification No. 2502239 may alternatively be employed if desired, instead of those described above.

The specimen attachments such as specimen mountings or specimen suspending attachments specimen heating means and/or specimen cooling means, as well as specimen movement devices are not limited to the construction shown but may be of any desired type.

If for example direct heating of the specimen is desired, inductive heating may be used or heating by means of electro-magnetic waves, if for example the specimen carrier consists of a diathermic material such as, for example, plastics. The choice of the type of heating or cooling depends above all on the desired temperature range. If especially low temperatures are to be obtained so called cryogenic media as well as liquid nitrogen may be used as the cooling liquid. The temperature adjustment of the individual zones of the temperature profile over the length may be made according to a pre-selected programme in a manner known per se.

For programming, the test program may, for example, be put into the memory (PROM) of a microprocessor or onto a data carrier which may be plugged into an input unit for the micro computer and automatically read and transfer the program data.

Claims (7)

1. Apparatus for testing a specimen to ascertain its resistance to light and weather having a testing space within a chamber which contains at least one gas-discharge radiator and reflector and a selectively-reflecting filter device for simulation of sunlight or simi lar desired radiation or climatic conditions as well as specimen carriers or holders for elongated areal specimens, characterised by a device for the generation of a temperature gradient in the specimen.

2. Apparatus as claimed in claim 1, characterised by means for the generation of a linear specimen tempera+.ure gradient over the range of measurement.

3. Apparatus as claimed in claim 1 or 2, comprising a specimen carrier heated and/or cooled at different temperatures at the surface facing the specimen.

4. Apparatus as claimed in claim 3, comprising means for effecting a direct heating and/or cooling of the specimen carrier on placing the specimen on the surface facing the beam source and/or the specimen for suspension in containers of suitable type.

5. Apparatus as claimed in claim 3 or 4, wherein the specimens and/or the specimen carriers are divided lengthwise into zones of different temperatures which are measured by sensors and adjusted according to a set program.

6. Apparatus as claimed in claim 5, wherein means are provided to move the specimen over the heating and/or cooling zones in the longitudinal direction.

7. Testing apparatus substantially as hereinbefore described with reference to any one of the Figures of the accompanying drawings.