Structural Deterioration
Irreversible change in the chemical structure and physical properties of textile fibres caused by exposure to heat, light, chemicals, or mechanical stress during manufacturing and use. This process involves the breaking of the long molecular chains that give the fibre its strength and flexibility. As the chains are shortened, the material loses its integrity, leading to a decline in performance characteristics like tensile strength, elasticity, and color fastness.
Polymer degradation is a constant concern in the production of synthetic fibres like polyester and nylon, as well as natural fibres like cotton and silk. Understanding the triggers for this breakdown is essential for developing durable textile products.
Chain Scission
Molecular mechanism behind the deterioration often involves the cleavage of the bonds holding the polymer units together, a process known as chain scission. This can be caused by the absorption of high-energy ultraviolet radiation, which triggers a series of free radical reactions that attack the polymer backbone. Thermal energy can also cause the chains to vibrate and break, particularly in the presence of oxygen or moisture.
In some cases, the degradation is a result of chemical attack, such as when acids or alkalis react with the functional groups of the polymer. This results in a permanent loss of molecular weight, which shows up as a decrease in the viscosity of the polymer when dissolved in a solvent. The rate of this reaction increases significantly at higher temperatures and under high humidity.
Performance Loss
Physical manifestations of the chemical breakdown include yellowing, brittleness, and a general loss of surface smoothness. A fabric suffering from polymer degradation will often feel dry or “crunchy” to the touch and will tear much more easily than a fresh sample. In synthetic fibres, the degradation can also lead to the formation of small cracks or pits on the surface, which increase the tendency for pilling and snagging.
These changes are not just cosmetic, as they directly affect the safety and longevity of the garment. For technical textiles used in outdoor applications, such as awnings or safety harnesses, the loss of strength can be catastrophic. Testing labs use accelerated aging chambers to simulate years of exposure and predict how the polymer will hold up over time.
Failure Analysis
Investigating the cause of a textile failure often requires a detailed look at the chemical state of the fibres to determine if degradation has occurred. Techniques like infrared spectroscopy and gel permeation chromatography allow scientists to identify the specific chemical changes and the extent of the molecular weight loss. This information helps manufacturers to improve their formulations by adding stabilizers or UV absorbers that can slow the rate of decay.
If the degradation happened during the dyeing or finishing stage, the process parameters must be adjusted to reduce the thermal or chemical load on the fabric. By identifying the specific trigger, the factory can prevent similar issues in future production runs. The final goal is to ensure that the textile maintains its properties throughout its intended lifespan.
