A Study on the Durability Properties of Textile Membranes for Architectural Purposes

The durability of textile membranes in outdoor architectural applications is a key factor to be considered in a specific project design. The degradation of the polymers within the coating and its propagation to the fibres contributes to the loss of functional performance, mainly in terms of mechanical properties. The aim of this work was to study the durability of two architectural membranes: one produced with polyester fibre coated with polyvinylchloride (PVC) and other produced with glass fibre coated with polytetrafluorothylene (PTFE) at the initial stages of environmental exposure. These materials were subjected to an in-situ degradation in a real environment and a rapid degradation by the action of moisture and ultraviolet radiation in an accelerated aging chamber over a period of 2160 hours (3 months). The effect of these agents on the degradation and thus the durability of the membranes was evaluated by the loss of mechanical performance (tensile strength test) and thermal performance levels (Alambeta test). In addition to mechanical and thermal analyses, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis were performed, in order to understand the effect of the degradation agents on the surface of the membranes. The mechanical performance of the polyester/PVC membranes has shown unchangeable properties, while the glass fibre /PTFE membrane has presented a reduction on tensile strength properties. These reduction was more significant when the membrane were subjected to the accelerated degradation test, showing a decrease of resistance of about 34% and 43% on longitudinal and transversal direction, respectively for the period of 2160 hours. SEM images of polyester/PVC membranes did not show any significant difference over time, however EDS analysis showed a loss of 52% of the chlorine element. For glass fibre /PTFE membrane, SEM and EDS analysis didn't show any significant difference over degradation time.