In this month's article, we will try to resolve a concern that has been common among our customers, the behavior of plastic materials in the face of environmental conditions and the passage of time.

In order to be able to objectively evaluate the degradation suffered by different plastic materials in the face of external, environmental and/or climatic factors, specific tests are carried out to determine their evolution. All artificial aging tests are carried out under certain conditions following the regulations determined by the relevant test.

The ISO 4892 standard determines the methods of exposure to laboratory light sources, using a test that allows the simulation of the environmental conditions to which plastics will be subjected during their useful life.

To this end, it is common for manufacturers to improve the performance of their products, to use accelerated aging cameras that reproduce the damage caused by sunlight, rain and dew. In a few days or weeks, these devices simulate the weathering effects caused by the environment on exposed materials. In this way, an approximate assessment can be made of their evolution over the course of months or even years out in the open. That said, clarify that, although they are tests that strictly follow the applicable regulations, their result does not correspond to an equivalent to so many years of warranty, it is simply a tool for analyzing the behavior of different materials in the face of the same aggression and certain environmental conditions.The method of measuring the resistance of materials to sun exposure is carried out in the laboratory using accelerated aging equipment, distinguishing between those that use arc lamps xenon (ISO 4892-2:2016) and those using fluorescent UV radiation lamps (ISO 4892-2:2016). The type of lamp, the test conditions and the exposure time depend on the type of material to be evaluated and the requirements for suitability for use. Fluorescent UV lamps simulate the critical spectrum of short-wave ultraviolet (UV) radiation and reproduce the effect of sunlight on physical properties, such as surface degradation and resistance. Meanwhile, xenon arc lamps are used to reproduce in the most realistic way possible the full spectrum of sunlight, including ultraviolet, visible light and infrared radiation. For certain end uses, exposure to the full spectrum is necessary in order to provide an exact simulation, and thus evaluate the color change and its photoresistance. Once the objectives of the simulations, the test method and the measuring devices used for this purpose have been described, we will proceed to present a concrete example by comparing products from our own catalog. Thus, for this comparative study we are going to use two types of compact polycarbonate that are part of our offer. The PC 05 Lexan Exell D (with UV treatment) and the PC 03 Lexan 9030 (without UV treatment). And their behavior when subjected to intensive exposure to ultraviolet UV rays. In this case, these materials have been subjected to an accelerated aging test as stipulated by the ISO 4892-2 standard, for xenon lamps. Specifically, using a Weather - O - Meter (WOM) model ATLAS CI5000, which simulates the exposure of plates to UV radiation, heat and water and determines the effects they cause on them when exposed to the final use of the plate. Specifically, in this case, UV filters (CIRA indoor/outdoor sodalime) and programmable rain cycles have been used to generate hypotheses of common environmental conditions.

Essay sheet

Tables. Delta yellowing index (YI) and light transmission (LT) after the xenon test.

Images before and after the xenon test (ISO 11341).

The test result shows that the plate, without UV protection, shows obvious signs of color change and alteration of the finish. On the other hand, with UV protection on both sides, after 9-113 hours of exposure to the xenon lamp, the color is only slightly altered and the finish remains stable.