Papers by Keyword: Surface Degradation

Abstract: Sandwich cladding panels, based on PUR, PIR or similar foams, are frequently used for insulation of all types of assembled industrial, store and sporting halls, as well as of commercial and administrative objects, namely for those with controlled interior temperature, and represent an advanced and modern building element. However, favourable properties of such panels are limited by the long-time degradation of the coating layer, caused by various climatic influences, as intensive sun radiation, wind, rain, frost etc., resulting in the modification of surface emissivity. Increased thermal absorptance of panels can be observed namely on south-oriented walls. This paper pays attention to the surface treatment of panels, comparing their physical emissivity in the range of wavelengths of sunrays, depending on the measure of their degradation, due to the amount of absorbed sun radiation. The significance of such influence is quantified, utilizing the well-considered measurement methodology.

Abstract: This study provides an overview of the effects of prolonged acid attack on the surface of PTFE gaskets, assessed using Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The PTFE analysed originates from two manufacturers in form of Teflon adhesive tapes, used as gaskets in an ultrasonic tyre moulds cleaning plant (UMCS). The gaskets were exposed to various acid baths, temperature and ultrasonic waves, and shown anomalous damage and surface degradation in a relatively short operation time. The analyses here reported have been aimed at investigating this unusual behaviour. PTFE samples have been treated with different acid mixes to evaluate possible different aging effects. Both surface and core have been analysed after aging, providing evidence of the degradation phenomena. In particular, different acid treatments have highlighted different response of PTFE and differences among manufacturers.

Abstract: Polyimides (PIs) are widely used in electronics wherein high temperature (HT) insulating layers are needed. Like other polymers used in HT and in ambient atmosphere, polyimides are subject to the thermal and thermo-oxidative degradations. The thermo-oxidative aging can lead to the material dielectric properties degradation and then to the device failure. Therefore, it is important to study the thermo-oxidative aging effect on the dielectric properties of PI thin films, in order to predict their lifetime. During the thermo-oxidative aging of PI films deposited on stainless steel substrate at 300 °C in air, electrical (dielectric loss, DC conductivity, breakdown voltage), physical (thickness and surface profile) and physicochemical (FTIR) properties, have been monitored for different film thicknesses. Results are analyzed and discussed in order to choose the suitable life end point criterion, and to estimate the mean time to reach it in such aging conditions.