Chemical Degradation
Irreversible breaking of the flexible polyether or polyester chains in a polyurethane elastomer molecule destroys the elastic recovery of synthetic yarns. This chemical damage, known as soft segment scission, occurs under the influence of heat, light, or reactive chemical agents.
Environmental Origin
Exposure to ultraviolet radiation or atmospheric pollutants initiates the chemical breakdown of the flexible blocks. Chlorine in swimming pools and ozone in the air act as strong oxidants that attack the ether or ester linkages. This chemical reaction leads to soft segment scission, which gradually degrades the polymer chain and shortens the life of the fiber.
When synthetic yarns are exposed to both sunlight and heat, the rate of this oxidative degradation increases, causing the elastic garments to lose their stretch within a few weeks of use.
Mechanical Consequence
Reduced chain continuity in the flexible regions reduces the stretch capacity of the fabric. Garments suffer from permanent bagginess and lose their shape-retention properties because the degraded soft segments can no longer stretch or pull back. Laboratory testing shows a drop in the recovery force of the yarn.
Stabilization Strategy
Incorporating protective chemical additives into the polymer dope during spinning reduces the degradation rate. Antioxidants and ultraviolet absorbers shield the soft segments from oxidative attack.
