Impact of the LED-based light source working regime on the degradation of polymethyl methacrylate

The popularity of LED-based luminaires has increased enormously in recent years. Every such luminaire consists of several elements including a polymer-based transparent housing, yet some of the ageing aspects of specific luminaire materials have not been investigated. In this paper, we present research aimed at determining the impact of LED lamp powering mode on polymer material deterioration. In the experiment, three LED lamp operating systems based on two different pulse width modulation units and one DC power source were used to induce deterioration in a polymethyl methacrylate sample. Two types of LEDs, white and ultraviolet, were considered as the most significant in terms of the impact on the material. Observations of the surface's morphological changes were performed to enable non-destructive investigation of the degradation of the exposed samples. In order to obtain high roughness detection sensitivity, atomic force microscopy was used. We observed various ageing ratios of the material, despite the fact that total average optical energy for specific wavelengths was equal for all samples. The importance of these findings for designing modern luminaires is discussed.