Photodegradation of thermally bonded polyester nonwovens

Durable polyester nonwoven fabrics have a finite lifetime determined by a number of factors. Important among these is photodegradation, where prolonged exposure to sunlight causes damage to the chemical linkages of the polymers resulting in the loss of desirable characteristics.

The purpose of this study was to investigate the degradation resulting from exposure to the ultraviolet component of sunlight in terms of changes in molecular weight, polydispersity, and physical performance behavior of thermally bonded polyester nonwovens. Fabrics representative of the nonwoven interlining market were made according to an initial determination of optimal base/binder fiber composition and bonding conditions. Samples were exposed to ultraviolet light in the xenon-arc Weatherometer for 100 to 400 hours in 50 hour increments. Flexural rigidity, tenacity, and elongation were analyzed before and after exposure, and viscosity, gel permeation chromatography, and differential scanning calorimetry were measured after exposure to determine the effect of exposure to ultraviolet light on the nonwoven fabric.

Overall, a decrease in all average molecular weight averages and an increase in polydispersity were observed. Chain scission reactions appeared to predominate; however, some evidence exists to support a degree of crosslinking between 200 and 300 hours of exposure to ultraviolet light. Mechanical properties of flexural rigidity, tenacity, and extension followed trends exhibited by molecular weight, decreasing overall.

Additional investigation is recommended to determine the contribution of base fiber, binder fiber and bond strength to the failure of mechanical properties. Longer exposure time periods are needed to more realistically assess damage, as well as investigations using layered systems such as draperies to more adequately reflect actual end use testing.